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Understanding the dynamics of attributes of medium and short cycle rice cultivars under nitrogen effect

Compreendendo a dinâmica de atributos de cultivares de arroz de ciclo médio e curto sob efeito do nitrogênio

ABSTRACT:

Nitrogen (N) is the element supplied by the soil that limits the development of irrigated rice. The hypothesis of the present is that to meet higher demand for N by the plant due to the higher potential yield, it is not necessary to apply a higher dose of N fertilizer. This studyevaluated the efficiency of N utilization, the rate of growth and accumulations of N by plants and the grain yield of two rice cultivars, short cycle and medium cycle, with and without N fertilization. A field experiment was installed in the Rio Grande do Sul, southern Brazil. The treatment factors evaluated were cultivar, with medium and short cycles, with doses of 0 and 150 kg N ha-1. Growth curves, absorption rate, N content and leaf area index over time, root area and grain yield were analyzed. The medium cycle cultivar has a greater potential to explore the environment when compared to the short cycle rice cultivar, both for greater leaf area and root area per cultivation area, as well as for longer exploration times. Thus, the medium cycle cultivar has greater N utilization efficiency and higher grain yield.

Key words:
irrigated rice; nitrogen fertilization; growth curve; absorption

RESUMO:

O nitrogênio é o elemento fornecido pelo solo que mais limita o desenvolvimento do arroz irrigado. A hipótese do presente trabalho é que para atender a uma maior demanda de nitrogênio pela planta devido ao maior potencial de rendimento, não é necessário aplicar uma dose maior de fertilizante nitrogenado. O objetivo do estudo foi analisar o efeito do potencial produtivo de cultivares de arroz na resposta ao nitrogênio. Um experimento de campo foi instalado no Rio Grande do Sul, sul do Brasil. Os fatores de tratamento avaliados foram cultivar, com ciclos médio e curto sob doses de 0 e 150 kg N ha-1. Foram analisadas curvas de crescimento, marcha de absorção, teor de nitrogênio e índice de área foliar ao longo do tempo, área radicular e produtividade de grãos. A cultivar de ciclo médio apresenta maior potencial de exploração do ambiente quando comparada a cultivar de arroz de ciclo curto, tanto pela maior área foliar quanto pela maior área superficial da raiz por área. Assim, a cultivar de ciclo médio tem maior capacidade de exploração de recursos e maior eficiência no aproveitamento do nitrogênio, o que é de grande importância para uma agricultura mais sustentável.

Palavras-chave:
arroz irrigado; adubação nitrogenada; curva de crescimento; marcha de absorção

INTRODUCTION:

The irrigated rice cultivation in southern Brazil is the most technically advanced rice production system in the country and the regions with the highest grain yield globally (CARLOS et al., 2020CARLOS, F. S. et al. Integrated crop-livestock systems in lowlands increase the availability of nutrients to irrigated rice. Land Degradation & Development, v.31, n.18, p.2962-2972, 2020. Available from: <Available from: https://onlinelibrary.wiley.com/doi/10.1002/ldr.3653 >. Accessed: Apr. 24, 2021.
https://onlinelibrary.wiley.com/doi/10.1...
; SOSBAI, 2018SOSBAI. Arroz Irrigado - Recomendacões técnicas da pesquisa para o Sul do Brasil. Cachoerinha-RS, 205 p, 2018.; SOUSA et al., 2021SOUSA, Rogério Oliveira De et al. No-tillage for flooded rice in Brazilian subtropical paddy fields: history, challenges, advances and perspectives. Revista Brasileira de Ciência do Solo, v.45, 2021. Available from: <Available from: https://www.rbcsjournal.org/article/no-tillage-for-flooded-rice-in-brazilian-subtropical-paddy-fields-history-challenges-advances-and-perspectives/ >. Accessed: Nov. 29, 2021.
https://www.rbcsjournal.org/article/no-t...
). The crop’s yield has increased consistently, especially over the past decade. In the Rio Grande do Sul, the average crop yield reached 9,010 Kg ha-1 in the crop season 2020/2021 (IRGA, 2021IRGA. Produção municipal - Safra 2020/2021. Serviçoes e informações - Safras, [S.l.], 2021. Available from: <https://irga.rs.gov.br/boletim-de-resultados>.
https://irga.rs.gov.br/boletim-de-result...
). Such yield results from the use of cultivars with high genetic potential and technical advances in crop management, mainly regarding irrigation, fertilization (CARDOSO et al., 2020CARDOSO, E. F. et al. Phosphate fertilization for rice irrigated in soils with different phosphorus adsorption capacities. Archives of Agronomy and Soil Science, v.68, n.1, p.89-100, 2020. Available from: <Available from: https://www.tandfonline.com/doi/full/10.1080/03650340.2020.1827233 >. Accessed: Jan. 10, 2022.
https://www.tandfonline.com/doi/full/10....
; CARLOS et al., 2021CARLOS, F. S. et al. A long‐term no‐tillage system can increase enzymatic activity and maintain bacterial richness in paddy fields. Land Degradation & Development, v.32, n.6, p.2257-2268, 2021. Available from: <Available from: https://onlinelibrary.wiley.com/doi/10.1002/ldr.3896 >. Accessed: Apr. 24, 2021.
https://onlinelibrary.wiley.com/doi/10.1...
; OGOSHI et al., 2020OGOSHI, C. et al. Influence of Blast on the Nutrition and Yield of Irrigated Rice in Southern Brazil. Journal of Soil Science and Plant Nutrition, v.20, n.3, p.1378-1386, 2020. Available from: <Available from: https://link.springer.com/article/10.1007/s42729-020-00219-9 >. Accessed: Jan. 17, 2022.
https://link.springer.com/article/10.100...
), sowing time density and weed control (SOSBAI, 2018SOSBAI. Arroz Irrigado - Recomendacões técnicas da pesquisa para o Sul do Brasil. Cachoerinha-RS, 205 p, 2018.).

The fertilizer doses with nitrogen (N), phosphorus (P) and potassium (K) has increased over time in proportion to the grain yield despite the fact the maximum recommended doses in the 1990s were 90, 60 and 60 kg ha-1 of N, P2O5 and K2O, the current maximum recommendations for very high yield expectations are 150, 80 and 125 kg ha-1 of N, P2O5 and K2O, respectively (SOSBAI, 2018SOSBAI. Arroz Irrigado - Recomendacões técnicas da pesquisa para o Sul do Brasil. Cachoerinha-RS, 205 p, 2018.). Although, it is stated that, on average, such doses of fertilizers have an economic return at current prices, it is possible that in many cases high doses are used much more as a guarantee of obtaining high yields than because of the real need for culture. That is, in many cases it is possible that high yields can be obtained with lower fertilizer doses than currently recommended.

Furthermore, the recommendations presented in SOSBAI (2018)SOSBAI. Arroz Irrigado - Recomendacões técnicas da pesquisa para o Sul do Brasil. Cachoerinha-RS, 205 p, 2018. do not consider that there may be differences in the responses of rice cultivars to N, solely based on soil organic matter content and expected grain yield. To reach this level of specification, more in-depth knowledge of nutritional requirements throughout the crop cycle and its interaction with other factors of production is required.

The efficiency of using N refers to the plant’s ability to use N for grain production (SHARMA et al., 2018SHARMA, N. et al. Phenotyping for nitrogen use efficiency: Rice genotypes differ in N-Responsive germination, oxygen consumption, seed urease activities, root growth, crop duration, and yield at low N. Frontiers in Plant Science, v.9, p.1452, 2018. ). Currently, several strategies are developed worldwide to improve the efficiency of the use of N-fertilizers, so that the losses that occur in the flooded system, through processes such as volatilization, leaching and denitrification can be mitigated (AN et al., 2018AN, N. et al. Agronomic and environmental causes of yield and nitrogen use efficiency gaps in Chinese rice farming systems. European Journal of Agronomy, v.93, p.40-49, 2018. Available from: <Available from: https://www.sciencedirect.com/science/article/pii/S1161030117301673 >. Accessed: Jan. 12, 2022.
https://www.sciencedirect.com/science/ar...
; CHEN, G. et al., 2015CHEN, G. et al. Do high nitrogen use efficiency rice cultivars reduce nitrogen losses from paddy fields? Agriculture, Ecosystems & Environment, v.209, p.26-33, 2015. Available from: <Available from: https://www.sciencedirect.com/science/article/pii/S0167880915000778 >. Accessed: Nov. 08, 2021.
https://www.sciencedirect.com/science/ar...
; HUANG, L. et al., 2019HUANG, L. et al. Coordination of high grain yield and high nitrogen use efficiency through large sink size and high post-heading source capacity in rice. Field Crops Research, v.233, p.49-58, 2019. Available from: <Available from: https://www.sciencedirect.com/science/article/pii/S0378429018315132 >. Accessed: Jan. 12, 2022.
https://www.sciencedirect.com/science/ar...
). In addition to the adequacy of doses, the regular application of N in the form of instalments as well as the introduction of sustainable management practices such as green manure can help to reduce losses in irrigated cultivation and assist in increasing the efficiency use of applied N (ALAM et al., 2019ALAM, M. A. et al. Nitrogen transformation and carbon sequestration in wetland paddy field of Bangladesh. Paddy and Water Environment, v.17, n.4, p.677-688, 2019. Available from: <Available from: https://link.springer.com/article/10.1007/s10333-019-00693-7 >. Accessed: Jan. 14, 2022.
https://link.springer.com/article/10.100...
; CARLOS et al., 2022CARLOS, F. S. et al. Soybean crop incorporation in irrigated rice cultivation improves nitrogen availability, soil microbial diversity and activity, and growth of ryegrass. Applied Soil Ecology, v.170, p.104313, 2022. Available from: <Available from: https://linkinghub.elsevier.com/retrieve/pii/S0929139321004364 >. Accessed: Nov. 15, 2021.
https://linkinghub.elsevier.com/retrieve...
; THAKUR; MANDAL; RAYCHAUDHURI, 2020THAKUR, A. K.; MANDAL, K. G.; RAYCHAUDHURI, S. Impact of crop and nutrient management on crop growth and yield, nutrient uptake and content in rice. Paddy and Water Environment, v.18, n.1, p.139-151, 2020. Available from: <Available from: https://link.springer.com/article/10.1007/s10333-019-00770-x >. Accessed: Jan. 14, 2022.
https://link.springer.com/article/10.100...
).

In Rio Grande do Sul six rice regions are well defined according to the prevailing climatic variables in each with different yield potentials (SOSBAI, 2018SOSBAI. Arroz Irrigado - Recomendacões técnicas da pesquisa para o Sul do Brasil. Cachoerinha-RS, 205 p, 2018.). In addition, the cultivars in use have different genetic potentials (KLERING et al., 2008KLERING, E. V. et al. Modelagem agrometeorológica do rendimento de arroz irrigado no Rio Grande do Sul. Pesquisa Agropecuária Brasileira, v.43, n.5, p.549-558, 2008. Available from: <Available from: http://www.scielo.br/j/pab/a/m7LBGXcMXLfNZQMFHR9gJQv/ >. Accessed: Jan. 14, 2022.
http://www.scielo.br/j/pab/a/m7LBGXcMXLf...
). Therefore, the quantitative requirements of N for the crop to reach its maximum yield in each crop must vary between cultivars and between climatic regions. From the point of view of fertilization practice, it leads to the following question: to meet a higher demand for N by the rice plants due to the higher potential yield, is it necessary to apply a higher doses of N fertilizer? As a hypothesis, the answer is no. When a plant grows more, either due to its genetic potential or to more appropriate environmental conditions, the plant’s ability to acquire nutrients from the soil increases proportionately. The increase in the root system as a result of increased plant growth alone already compensates for the need for additional absorption. Experimentally, this comparison is difficult to make between regions or even between different places within a region because the differences between soils can mask the results. In the same place, comparing cultivars with different genetic potentials, the hypothesis can be tested. In this case, the research hypothesis is that the medium cycle cultivar has a greater capacity to exploit the resources of the environment, greater N utilization efficiency and achieves higher yields than a shorter cycle cultivar.

The theoretical basis to justify any differences in yield between cultivars, as well as the effects of N on yield can be sought from the analysis of the growth of the different organs and of the absorption and distribution of N among the plant organs along with its development cycle, under conditions of insufficient and sufficient N supply. In Brazil, there are no previous studies comparing cultivars from different cycles in relation to N utilization and grain yield.

Thus, the objective of this research was to evaluate the efficiency of N utilization, the rate of growth and accumulation of N by plants and the grain yield of two rice cultivars, of short and medium cycle, with and without N fertilization

MATERIALS AND METHODS:

Site description

The experiment was conducted in the municipality of Manoel Viana, which is an important irrigated rice-producing regions in the state of Brazil. Located by definition of the geographical coordinates 29º 25’ 34.64” S and 55º 43’ 49.78” W, at an altitude of 81 m. The soil is classified as Haplic Luvisol (STRECK et al., 2008STRECK, E. . et al. Solos do Rio Grande do Sul. 2. ed. Porto Alegre: Emater-RS: 222 p, 2008.) and flat relief. The region’s climate is classified as humid temperate with hot summer (Cfa), according to the Köppen classification with an average temperature of 20.7 ºC and annual rainfall of 1371 mm year-1. The location of the experimental area is shown in figure 1.

Figure 1
Experimental location in the municipality of Manoel Viana, state of Rio Grande do Sul, Brazil. Adapted from Sousa et al. (2021SOUSA, Rogério Oliveira De et al. No-tillage for flooded rice in Brazilian subtropical paddy fields: history, challenges, advances and perspectives. Revista Brasileira de Ciência do Solo, v.45, 2021. Available from: <Available from: https://www.rbcsjournal.org/article/no-tillage-for-flooded-rice-in-brazilian-subtropical-paddy-fields-history-challenges-advances-and-perspectives/ >. Accessed: Nov. 29, 2021.
https://www.rbcsjournal.org/article/no-t...
).

For the installation of the experiment, a survey of the chemical attributes of the area, was previously made. Table 1 shows the main results of the soil analysis, carried out before the installation of the experiment. To certify the homogeneity of the site, and mesh samplings were carried out every five meters. In each sample, the contents of phosphorus, potassium, organic carbon and pH in water and in Shoemaker, McLean, Pratt (SMP) buffer solutions were determined (TEDESCO et al., 1995TEDESCO, M. et al. Análises de solo, plantas e outros materiais. 2. ed. Porto Alegre-RS, Brazil, 175 p, 1995.).

Table 1
Chemical characterization performed before the installation of the experiment for the parameters pH in water, effective CEC, CEC at pH 7.0, Aluminum Saturation (AlS), Bases Saturation (BS), organic matter, phosphorus (P) and potassium (K).

Experimental design and description

The treatment factors evaluated in this study were factor (1) cultivar (C), medium and short cycle rice cultivar and factor (2) nitrogen dose (N), with 0 kg N ha-1 and 150 kg N ha-1. The N fertilizer was urea (46% N) from the company Yara Brasil®. The dose 0 kg ha-1 was added to confirm the response to the N applied. Two cultivars from different cycles and with different yield potentials were used to observe whether the period of cycle duration influences the use of N. The short cycle cultivar takes 83 days until full flowering and 115 days until maturation. The short cycle cultivar is IRGA 417, and it was widely cultivated in the early 2000s in Brazil. The medium cycle cultivar takes 96 days until full flowering and 132 days until maturation (SOSBAI, 2018). The medium cycle cultivar is IRGA 424, and it is the most sowed cultivar in Brazil and Latin America in the Clearfield® version (CL). The treatments consisted of varying the levels of N for each cultivar in a 2x2 factorial scheme.

The experimental units were plots with dimensions of 7 x 10 m. The experiment was laid out in strip plot design with three replications. The plots received the same procedures of soil preparation, basic fertilization, seedings, control of invasive plants, pests and diseases, and water management. All crop management procedures are in accordance with the instructions described in SOSBAI (2018), except treatments with N levels. Certified seeds with known germination percentage were used, the sowing density used was sufficient to obtain a population of 300 plants m-2 for both cultivars. For the treatment that had N fertilization, it was carried out with the application of 10 kg ha-1 in the sowing and 140 kg ha-1 in coverage, 50% of the dose when the plants had three expanded leaves when the start of tillering (15 days) and the other fraction (50%) was applied at the end of the vegetative phase (55 days for short cycle cultivar and 65 days for medium cycle cultivar).

Sampling and analyses

The response variables observed were N accumulated and plant growth, growth was evaluated through the accumulation of dry mass and increase in leaf area, root area and grain yields were also evaluated. The method of observation of the accumulation of dry matter and N was by collecting samples of plant tissue, performed at average intervals of 15 days, starting from the phenological stage V2 (COUNCE; KEISLING; MITCHELL, 2000COUNCE, P. A.; KEISLING, T. C.; MITCHELL, A. J. A Uniform, Objective, and Adaptive System for Expressing Rice Development. Crop Science, v.40, p.436-443, 2000. Available from: <Available from: http://uarpp.uark.edu/Publications/Preharvest characterizatioin/Counce et al 2000 Crop Sci.pdf >. Accessed: May, 29, 2017.
http://uarpp.uark.edu/Publications/Preha...
). So, eight collections were made in the short cultivar and ten in the medium cycle cultivar. Collections were made in each experimental unit, totaling three samples, one in each replicate. Each collection consisted of the sampling of 1 linear meter irrigated rice plants that totalled 0.158 m2 per sampling date in each replicate.

All samples of plant tissue were dried at a temperature of 60 ºC, in a forced ventilation for 72 hours oven until they reach constant weight. After being properly dried, they were partitioned into stems, leaf sheath, leaf blade, panicle and dead tissue. The dry matter (DM) of the plants was weighed with milligram precision and then taken to the Laboratory of Soil and Vegetable Tissue Analysis to determine the N concentration (TEDESCO et al., 1995TEDESCO, M. et al. Análises de solo, plantas e outros materiais. 2. ed. Porto Alegre-RS, Brazil, 175 p, 1995.). So that the sum of the DM of all the organs constitutes the Dry Matter of the Aerial Part (DMAP) in each season, and the Dry Matter of the Panicle (DMP) obtained by the direct weighing of the panicle. The weighted average of the N content of each season multiplied by their respective DMAP gave rise to Total Accumulated Nitrogen (TAN), in the same way the N accumulated in the panicle (NAP) was calculated by multiplying the N content in the panicle and its respective DMP.

The leaf area index (LAI) was calculated by the relation between the leaf area (LA) and the corresponding land surface (0.158 or 0.79 m2), obtaining leaf area per soil area (m2 m-2). The leaf area, in turn, was estimated at each collection, using the product of the dry mass of green leaves with the relationship between the mass and the leaf area. This relationship was determined at three different times, the area was estimated in twelve leaves per experimental unit, and these leaves were properly dried and weighed to obtain the dry mass relationship with the area.

Root collection was performed during full flowering at the same time for all cultivars, three replicates per plot were collected. The collection was carried out through a monolith with a volume of 1485.2 cm³, the dimensions of which were 20 cm deep, 15.8 cm wide (between lines) and 4.7 cm long, which was inserted so that the between line was in the centre of the width. The monoliths were submerged in dispersant (NaOH at 0.05 Mol L-1) for 24h. They were then washed in running water with the aid of a 2 mm sieve, after which the samples were properly cleaned and kept in the refrigerator in solution with water and toluene (0.25 ml). Subsequently, root length measurement was performed using the method described by TENNANT (1975TENNANT, D. A Test of a Modified Line Intersect Method of Estimating Root Length. The Journal of Ecology, v.63, n.3, p.995, 1975. Available from: <Available from: https://www.jstor.org/stable/2258617 >. Accessed: Dec. 20, 2021.
https://www.jstor.org/stable/2258617...
) and the estimated volume through wet weight and the Root Surface Area (RSA) by the ratio between volume and length.

For evaluation final grain yield, three repetitions per plot were used. The collections were carried out in a square meter and then traced, dried in a forced ventilation oven at a temperature of 60 ºC, cleaned in equipment for small and heavy samples on a precision scale. The obtained masses were corrected for the humidity of 13%. The correction in the moisture content allows uniform weight for the same moisture content in the grain, and the value of 13% was chosen because it is the moisture content in which the rice grain must be stored.

Calculation methodology and data analysis

Growth analysis was performed by adjusting sigmoid logistic equations with three parameters, for the accumulation of Dry Matter of the Aerial Part (DMAP) and Dry Matter of the Panicle (DMP) according to ALVAREZ, R. De C. F. et al. (2006ALVAREZ, R. C. F. et al. Marcha de absorção de nitrogênio de cultivares de arroz de terras altas com diferentes tipos de plantas. Científica, v.34, n.2, p.162-169, 2006. Available from: <Available from: http://www.cientifica.org.br/index.php/cientifica/article/view/114 >. Accessed: Jan. 14, 2022.
http://www.cientifica.org.br/index.php/c...
); FELIX ALVAREZ; COSTA CRUSCIOL; STEPHAN NASCENTE (2012). So that the regression adjustment was performed using the SigmaPlot software with Equation 1, with f Dry Matter (DM) expressed in g m-2 and x the time in Days After Emergency (DAE).

DM= a/(1+exp(-(x-x0)/b))(1)

Where: a is the parameter that delimits the maximum point of the curve; b is the parameter that defines the maximum slope of the curve; and parameter x0 establishes the value of x where y (DM) is equals to half of a.

Also evaluated were the Absolute Growth Rate (AGR), obtained through the derivative of the equation adjusted for DM and expressed in g m-2 day-1 shown in Equation 2 according to (ALVAREZ, Rita De Cassia Felix; CRUSCIOL; NASCENTE, 2012ALVAREZ, R. C. F.; CRUSCIOL, C. A. C.; NASCENTE, A. S. Análise de crescimento e produtividade de cultivares de arroz de terras altas dos tipos tradicional, intermediário e moderno. Pesquisa Agropecuária Tropical, v.42, n.4, p.397-406, 2012. Available from: <Available from: http://www.scielo.br/j/pat/a/5gtk8WMMcnBRMhk6b9cM8gn/ >. Accessed: Jan. 14, 2022.
http://www.scielo.br/j/pat/a/5gtk8WMMcnB...
), and the Relative Growth Rate (RGR) obtained through the quotient of AGR and DMAP expressed in g g-1 day-1 as shown in Equation 3 according to (ALVAREZ, Rita De Cassia Felix; CRUSCIOL; NASCENTE, 2012). Where M is the mass in grams and T the time in days.

AGR=dMdT(2)

RGR=AGRDMAP(3)

Equation 1 was also used to analyze the accumulation of N in the aerial part and in the panicle, with f N accumulated in the DM in the unit of g m-2 and x the time in DAE. Through the derivative of the adjusted equation for the accumulation of N, the Absolute Absorption Rate (AAR) expressed in g N m-2 day-1, Equation 4, proposed based on Equation 2 of AGR was obtained. And finally, the Specific Utilization Rate (SUR) was obtained through the ratio between AGR and the Total Accumulated Nitrogen (TAN) having as units g g-1 N Day-1 Equation 5. MN being the mass of N in grams and T the time in days.

AAR=dMNdT(4)

SUR=AGRTAN(5)

To analyze the efficiency of N, the following parameters were used, all estimated from the functions adjusted for the primary data: Apparent Nitrogen Recovery (ANR) obtained by the ratio between the difference of N accumulation with and without N application and the dose application of N fertilizer expressed as a percentage according to Equation 6 (FAGERIA; SANTOS; CUTRIM, 2007FAGERIA, N. K.; SANTOS, A. B.; CUTRIM, V. dos A. Produtividade de arroz irrigado e eficiência de uso do nitrogênio influenciadas pela fertilização nitrogenada. Pesquisa Agropecuária Brasileira, n.7, p.1029-1034, 2007. Available from: <Available from: https://www.scielo.br/j/pab/a/PFCwtJC6Z44H4BpHfqCVVVN/?format=pdf >. Accessed: Jan. 17, 2022.
https://www.scielo.br/j/pab/a/PFCwtJC6Z4...
). Nitrogen Use Efficiency (NUE) obtained by the quotient between DMAP and TAN expressed in g g-1 of N described in Equation 7 (MARIOT et al., 2003MARIOT, C. H. P. et al. Resposta de duas cultivares de arroz irrigado à densidade de semeadura e à adubação nitrogenada. Pesquisa Agropecuária Brasileira, v.38, n.2, p.233-241, 2003. Available from: <Available from: http://www.scielo.br/j/pab/a/NHVMrZwDHjjkgFmkMgC6Dsd/ >. Accessed: Jan. 14, 2022.
http://www.scielo.br/j/pab/a/NHVMrZwDHjj...
). Physiological Nitrogen Use Efficiency (PNUE) obtained through the ratio between Grain Yield (GY) and TAN expressed in g g-1 of N described in Equation 8, according to BORIN et al (2013BORIN, J. B. M. et al. Eficiência do uso do nitrogênio e produtividade do arroz, afetados pelo manejo da água de irrigação em gleinossolo háplico. Santa Maria-RS: VIII Congresso Brasileiro de Arroz Irrigado, 2013. p.4. ). Agronomic Assessment of Nitrogen Use Efficiency (AANUE) obtained because of the difference in grain yield with and without N application and the applied N dose expressed in g g-1 of N and described in Equation 9.

ANR=MN150-MN0D150(6)

NUE=DMAPNAT(7)

PNUE=GYNAT(8)

AANUE=P150-P0D150(9)

Where: MN150 is the accumulated mass of N at a dose of 150 kg ha-1 of N in g m2; MN0 is the accumulated N mass without application of N in g m-2; D150 dose of 150 kg ha-1 of N; GP grain yield in g m-2; P150 grain yield at the dose of 150 kg ha-1 of N in g m-2; P0 grain yield without application of N in g m-2.

Statistical analysis

To interpret the N dilution in the total dry matter (TDM), potential equations with two parameters were adjusted according to the function presented in Equation 10 (GASTAL; LEMAIRE, 2002GASTAL, F.; LEMAIRE, G. N uptake and distribution in crops: an agronomical and ecophysiological perspective. Journal of Experimental Botany, v.53, n.370, p.789-799, 2002. Available from: <Available from: https://pubmed.ncbi.nlm.nih.gov/11912222/ >. Acessed: Jan. 14, 2022.
https://pubmed.ncbi.nlm.nih.gov/11912222...
), which was adjusted by the R software. Being f the level of N in percentage and x time in DAE (where x≥1); so that, a defines the highest point of the curve (greatest y) and b define the level at which y stops falling (where b < 0).

f=axb(10)

Some attributes were submitted to ANOVA and when significant to the Tukey test (P < 0.05). The confidence interval assessed variables over time at a 95% significance level. A Pearson correlation was made between the attributes and parameters of the evaluated plants. All analysis of the data was conducted in the R statistical environment (R CORE TEAM, 2020R CORE TEAM. A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. - References - Scientific Research Publishing, 2020. Available from: <Available from: https://www.scirp.org/(S(351jmbntvnsjt1aadkposzje))/reference/referencespapers.aspx?referenceid=2882118 >. Accessed: May, 10, 2021.
https://www.scirp.org/(S(351jmbntvnsjt1a...
) with particular use of the packages nlme and ggplot2 (PINHEIRO; BATES, 2022PINHEIRO, J.; BATES, B. Nlme: Linear and Nonlinear Mixed Effects Models, 2022. Available from: <Available from: https://bugs.r-project.org >. Accessed: Jan. 14, 2022.
https://bugs.r-project.org...
). Principal component analysis was carried out where all the attributes and parameters of the analyzed plants were vectored to understand better the variations observed concerning the cultivar cycle and the N dose. For PCA analysis, the statistical software R was used.

RESULTS:

Grain yield and root surface area

The medium cycle cultivar was more productive than that of the short cycle, in both N levels (Figure 2). The medium cycle cultivar produced 9450 and 11640 kg ha-1, at levels of zero N and 150 kg ha-1 of N respectively, whereas the short cycle cultivar showed a grain yield of 7100 kg ha-1 without N and 10110 kg ha-1 with N fertilization (Figure 2). The response in root growth occurred more pronounced in the medium cycle cultivar, which had an increase of 46 m2 m-3 in the area explored by the roots by volume of soil, increasing from 205 m2 m-3 to 251 m2 m-3. The short cycle cultivar showed no increase in the area explored by the roots, exploring 122 m2 m-3 of soil with and without application of N fertilization (Figure 2).

Figure 2
Grain yield (A) and root surface area (B) of medium and short cycle cultivars submitted to two nitrogen levels, 0 kg N ha-1 and 150 kg N ha-1. Vertical bar shows average data of 3 replicates. Error bars show standard deviation. Tukey (P < 0.05) compares the cultivars at the respective dose.

Leaf area index (LAI)

The cultivars studied when cultivated without N fertilization had low leaf area indexes, 3.6 m2 m-2 in the medium cycle cultivar and 2.8 in the short cycle cultivar, both below the critical LAI. When grown with the application of 150 kg N ha-1, these showed a considerable increase in the LAI, with 2.8 m² of photosynthetically active leaf per m² of cultivation in the medium cycle and 2.7 in the short cycle (Figure 3). Thus, the precocious reached 5.5 LAI being within the ideal range, and cultivar with a medium cycle 6.4 above the critical LAI. Thus, in the medium cycle, the ideal LAI could be achieved with a lower N fertilization.

Figure 3
Temporal variation of the leaf area index (LAI) for nitrogen dose (A) and cultivar cycle (B) in irrigated rice submitted to two nitrogen levels: 0 kg N ha-1 and 150 kg N ha-1. Shaded areas represent 95% confidence bands of model fits.

Dry matter of the aerial part (DMAP) and absolute growth rate (AGR)

The adjustments obtained for DMAP showed a high degree of significance for both models, with a significance level of less than 0.01% by the F test. It was observed that the higher doses reflected in higher DMAP and that, regardless of the dose, the medium cycle cultivar showed higher DMAP than short cycle cultivar (Figure 4). Responses to the application of N fertilizer in the production of DMAP in the medium cycle cultivar represented an increase from 1899 g m-2 to 2588 g m-2 with an increase of 689 g m-2 equivalent to 27%, according to the model estimate for the end of the cycle. In the short cycle cultivar, the increase, estimated by the model for the end of the cycle, went from 1727 g m-2 to 2232 g m-2, increasing 505 g m-2 in DMAP, representing a 23% increase. The medium cycle cultivar showed a greater response in the production of biomass to N applied, because, in addition to having developed more DMAP, and it obtained an absolutely and proportionally greater increase in the accumulation of biomass. However, this greater response in biomass did not result in a greater response in grain production, since the increase in grain yield was greater in the short cycle cultivar (Figure 2). Regarding the absolute growth rate, a higher growth rate was observed at the 150 N dose and in the early cycle cultivar close to 80-90 DAE (Figure 5). Figure 6 shows the difference in growth of rice plants of cultivar IRGA 417 in the tillering phase, with and without nitrogen fertilization, in addition to the chlorosis symptoms characteristic of N deficiency in plants without nitrogen fertilization.

Figure 4
Temporal variation of dry matter of aerial part (DMAP) for nitrogen dose (A) and cultivar cycle (B) in irrigated rice submitted to two nitrogen levels: 0 kg N ha-1 and 150 kg N ha-1. Shaded areas represent 95% confidence bands of model fits.

Figure 5
Absolute growth rate for nitrogen dose (A) and cultivar cycle (B) in irrigated rice submitted to two nitrogen levels: 0 kg N ha-1 and 150 kg N ha-1. Shaded areas represent 95% confidence bands of model fits.

Figure 6
Aspect of the plants in the tillering phase - in the foreground a plot of cultivar IRGA 417 with N application and in the background on the left the same cultivar without N application.

Nitrogen accumulated in the aerial part and N use efficiency

As in the other variables analyzed, the accumulation of N was faster in the dose 150 N (Figure 7). When comparing cultivars, there was no greater N accumulation in the medium or short cycle cultivars (Figure 7). Note that the short cultivar has parameters b and x0 lower than the average cycle indicating that the accumulation of N in the biomass occurs more quickly in the short cultivar (Figure 7). The increase in TAN caused by N fertilization was much greater in the medium cycle cultivar (Figure 7), which for this reason obtained an Apparent Nitrogen Recovery (ANR) of 93%, while the short cultivar reached a RAN of 57% (Table 2). The Nitrogen Use Efficiency (NUE) and the Physiological Nitrogen Use Efficiency (PNUE) were higher in treatments that did not receive N. The Agronomic Assessment of Nitrogen Use Efficiency (AANUE) was higher in the short cultivar, being 20 g of grains per g of N and 14.6 g g-1 in the medium cycle (Table 2). Regarding the N level, the initial levels were relatively low, being 3.55 and 3.15% in the short cultivar with and without N, respectively (Figure 8). And in the medium cycle cultivar, the initial contents were 4.33 and 4.13% with and without N application, respectively. The treatments without N had a faster decay and reached very low levels of N in the tissue, according to the adjusted curve. The cultivar medium cycle reached a concentration of 0.75% and the short reached 0.81% at the end of the cycle.

Figure 7
Total accumulated N (TAN) for nitrogen dose and medium and short cycle cultivars of irrigated rice submitted to two N levels: 0 kg N ha-1 and 150 kg N ha-1. Shaded areas represent 95% confidence bands of model fits.

Table 2
Dry matter of the Aerial Part (DMAP), Total Accumulated Nitrogen (TAN), Apparent Nitrogen Recovery (ANR), Nitrogen Utilization Efficiency (NUE), Physiological Nitrogen Utilization Efficiency (PNUE), and Agronomic Assessment of Nitrogen Use Efficiency (AANUE) for medium and early cycle irrigated rice cultivars submitted to two levels of nitrogen: 0 kg N ha-1 and 150 kg N ha-1. The values of DMAP, TAN, N%, ANR, NUE and PNUE were estimated at physiological maturation from the previously adjusted models. Tukey (P < 0,05).

Figure 8
Nitrogen level for N dose (A) and cultivar cycle (B) in irrigated rice submitted to two N levels: 0 kg N ha-1 and 150 kg N ha-1. Shaded areas represent 95% confidence bands of model fits.

Pearson correlation and and principal component analysis between the different attributes of rice plants evaluated

Regarding the Pearson correlation it was observed that the yield had a positive relationship with LAI, RSA, DMAP, DMP, TAN and N (Figure 9). And the NUE had a negative relationship with the LAI and DMP.

The sum of PC1 and PC2, 87.2% of all observed variations were obtained (Figure 10). In the PCA it is also observed that both in the cultivar cycle (medium and short) and in the doses (0N and 150N) there is a clear grouping. Regarding the grouping by cultivar cycle, it is observed that there are a large number of variables (nue, nue, agr, rsa, yield, dmap, tan) that converge to the medium cycle cultivar (Figure 10). Thus, the medium cycle cultivar has a greater N use efficiency and greater grain yield.

Figure 9
Pearson correlation between the different attributes of rice plants evaluated in two doses of N and cultivars of short and medium cycle. lai: leaf area index, rsa: root surface area, dmap: dry matter of the aerial part, rgr: relative growth rate, dmp: dry matter of panicle, agr: Absolute Growth Rate, tan: total accumulated N, n: level of N, nue: N use efficiency and pnue: physiological N use efficiency. Significant at P < 0.05.

Figure 10
Principal component analysis comparing medium and short cycle cultivars (A) and N doses (B). lai: leaf area index, rsa: root surface area, dmap: dry matter of the aerial part, rgr: relative growth rate, dmp: dry matter of panicle, agr: Absolute Growth Rate, tan: total accumulated N, n: level of N, nue: N use efficiency and pnue: physiological N use efficiency. Significant at P < 0.05.

DISCUSSION:

The medium cycle cultivar is able to exploit the resources of the environment and transform into grain production, as it presents a larger leaf area and a higher biomass production per cultivation area, in addition to a larger root area per volume of soil, these characteristics revert to production. However, the short cultivar showed a greater increase in grain yield, even with an increase in LAI equal to the average cultivar, indicating that it is a genotype more responsive to N fertilization. Recent research observed that longer-cycle rice “indica” varieties had higher N utilization efficiency and higher yields than shorter cycle rice varieties (SHARMA et al., 2018SHARMA, N. et al. Phenotyping for nitrogen use efficiency: Rice genotypes differ in N-Responsive germination, oxygen consumption, seed urease activities, root growth, crop duration, and yield at low N. Frontiers in Plant Science, v.9, p.1452, 2018. ).

If the growth pattern of a cultivar is well known, DMAP can be a useful tool to estimate its growth, thus assisting in deciding the amount of N to be applied. The greatest increase in the mass of panicles in the medium cycle cultivar may be because this cultivar continues tilling practically until the end of the cycle in the treatment with the application of N, always generating new panicles. (HUANG, M. et al., 2016HUANG, M. et al. The solar radiation-related determinants of rice yield variation across a wide range of regions. NJAS - Wageningen Journal of Life Sciences, v.78, p.123-128, 2016. Available from: <Available from: https://www.sciencedirect.com/science/article/pii/S1573521416300288 >. Accessed: Dec. 10, 2021.
https://www.sciencedirect.com/science/ar...
). HUANG et al. (2019)HUANG, L. et al. Coordination of high grain yield and high nitrogen use efficiency through large sink size and high post-heading source capacity in rice. Field Crops Research, v.233, p.49-58, 2019. Available from: <Available from: https://www.sciencedirect.com/science/article/pii/S0378429018315132 >. Accessed: Jan. 12, 2022.
https://www.sciencedirect.com/science/ar...
also observed greater grain yield when there is greater biomass production, the greater relative efficiency of N uptake and N accumulation after flowering. Dry matter production is directly influenced by solar radiation captured by plants. In addition, the DMAP is an attribute that is related to greater N utilization efficiencies and that is related to higher grain yield (HUANG, M. et al., 2016HUANG, M. et al. The solar radiation-related determinants of rice yield variation across a wide range of regions. NJAS - Wageningen Journal of Life Sciences, v.78, p.123-128, 2016. Available from: <Available from: https://www.sciencedirect.com/science/article/pii/S1573521416300288 >. Accessed: Dec. 10, 2021.
https://www.sciencedirect.com/science/ar...
).

The increase in leaf area benefited photosynthesis, accumulating more photoassimilates that is reversed in grain production. The increase in LAI also causes greater transpiration of the plant, due to the greater surface area of transpiration, consequently the absorption of nutrients increase through a greater mass flow. The increase in the root surface area allowed a greater absorptions of nutrients, ensuring better plant nutrition. In this way, the average cultivar increased the capacity to exploit the nutrients made available by the soil, together with the demands for nutrients to achieve greater grain yield. The short cultivar, on the other hand, increased grain yield and consequently demand with N fertilization but did not increase its capacity to absorb nutrients through the increase in RSA. This may be one of the factors that prevent the precocious one from reaching grain yield levels as high as medium cycle cultivars. So that the short cultivar has a higher AGR in the two doses of N when compared to the cultivar medium cycle. When comparing the growth rates obtained with those presented by other authors (ALVAREZ; CRUSCIOL; NASCENTE, 2012ALVAREZ, R. C. F.; CRUSCIOL, C. A. C.; NASCENTE, A. S. Análise de crescimento e produtividade de cultivares de arroz de terras altas dos tipos tradicional, intermediário e moderno. Pesquisa Agropecuária Tropical, v.42, n.4, p.397-406, 2012. Available from: <Available from: http://www.scielo.br/j/pat/a/5gtk8WMMcnBRMhk6b9cM8gn/ >. Accessed: Jan. 14, 2022.
http://www.scielo.br/j/pat/a/5gtk8WMMcnB...
) it is noted that the two cultivars have a higher AGR, with early cycle cultivar reaching double the value presented by this author. Possibly since the cultivars in the present study are cultivated under flood irrigation, which, in general, results in a more favourable condition for rice development. In work carried out by ALVAREZ et al 2012, upland rice was carried out only with supplementary irrigation and with older cultivars, which in general have less productive potential.

When we compare the ANRs obtained in this resarch with those presented by BORIN et al. (2013BORIN, J. B. M. et al. Eficiência do uso do nitrogênio e produtividade do arroz, afetados pelo manejo da água de irrigação em gleinossolo háplico. Santa Maria-RS: VIII Congresso Brasileiro de Arroz Irrigado, 2013. p.4. ), using the medium cycle cultivar, we found similar results that have an average of 80%, varying between 49 and 138%. However, FAGERIA et al (2007FAGERIA, N. K.; SANTOS, A. B.; CUTRIM, V. dos A. Produtividade de arroz irrigado e eficiência de uso do nitrogênio influenciadas pela fertilização nitrogenada. Pesquisa Agropecuária Brasileira, n.7, p.1029-1034, 2007. Available from: <Available from: https://www.scielo.br/j/pab/a/PFCwtJC6Z44H4BpHfqCVVVN/?format=pdf >. Accessed: Jan. 17, 2022.
https://www.scielo.br/j/pab/a/PFCwtJC6Z4...
) reached lower ANR in rainfed rice ranging between 23 and 37%, with an average of 29%. One of the factors that can contribute to high apparent N recovery by the medium cycle cultivar is its larger root surface area. In this way, the N absorbed more by the treatment with N fertilization comes not only from the absorption of the applied N, but also from the N made available by the soil. Since the higher RSA allows the medium cultivar to exploit the resources better available in the soil, consequently absorbing more N. In addition to the roots, the increase in the leaf area (Figure 3) can also contribute to the increase in N absorption because with its addition, the plant has greater transpiration, generating a greater mass flow of the nutrient.

The NUE of this research are superior to those presented by LOPES (1996LOPES, S. I. G. Curva de resposta à aplicação de nitrogênio nas cultivares IRGA 416 e Colombiano em Uruguaiana. Cachoerinha-RS, 1996. p.12. ) and LOPES (2000)LOPES, S. I. G. Resposta à aplicação de nitrogênio de quatro linhagens e quatro cultivares de arroz irrigado. Cachoerinha-RS, 2000. p.11. , which were respectively 11.8, 4.68 and 9, 99 grams of grains per gram of N. The results reported in these two works have lower NUE because they have older cultivars that are less responsive to N. In addition, there has recently been the adoption of new management practices that increase the use of N in the fertilizer by the crop, such as the application of the first N fertilization before flood irrigation and anticipation of the sowing time, which is favourable to an adequate development of the crop, and, consequently, use of Nitrogen from fertilization. They are similar to those reported by FAGERIA et al. (2007FAGERIA, N. K.; SANTOS, A. B.; CUTRIM, V. dos A. Produtividade de arroz irrigado e eficiência de uso do nitrogênio influenciadas pela fertilização nitrogenada. Pesquisa Agropecuária Brasileira, n.7, p.1029-1034, 2007. Available from: <Available from: https://www.scielo.br/j/pab/a/PFCwtJC6Z44H4BpHfqCVVVN/?format=pdf >. Accessed: Jan. 17, 2022.
https://www.scielo.br/j/pab/a/PFCwtJC6Z4...
) and BORIN et al. (2013BORIN, J. B. M. et al. Eficiência do uso do nitrogênio e produtividade do arroz, afetados pelo manejo da água de irrigação em gleinossolo háplico. Santa Maria-RS: VIII Congresso Brasileiro de Arroz Irrigado, 2013. p.4. ). When there was an adequate supply of N, the concentrations according to the adjusted functions were 1.18 and 1.26% of N for the medium and short cycle cultivars, respectively, very similar to the values reported in WITT et al. (1999WITT, C. et al. Internal nutrient efficiencies of irrigated lowland rice in tropical and subtropical Asia. Field Crops Research, v.63, n.2, p.113-138, 1999. Available from: <Available from: https://www.sciencedirect.com/science/article/abs/pii/S0378429099000313 >. Accessed: Oct. 02, 2021.
https://www.sciencedirect.com/science/ar...
) in Asia, FAGERIA; PRABHU (2004) FAGERIA, N. K.; PRABHU, A. S. Controle de brusone e manejo de nitrogênio em cultivo de arroz irrigado. Pesquisa Agropecuária Brasileira, v.39, n.2, p.123-129, 2004. Available from: <Available from: http://www.scielo.br/j/pab/a/q5SDFC6MdHbFvHctTg7qhyr/ >. Accessed: Jan. 17, 2022.
http://www.scielo.br/j/pab/a/q5SDFC6MdHb...
in Central Brazil and MUELLER (1980MUELLER, S. Influência da adubação nitrogenada sobre o rendimento e outros parâmetros de três cultivares de arroz irrigado. Universidade Federal de Pelotas, 1980. ) in South Brazil for maximum grain yield. There is a small difference between the levels of the cultivars, with the short cultivar having a slightly higher content in the two levels of N.

Cultivars that are more efficient in absorbing N have higher yields and dry matter gain as they have higher root oxidation activity and active root uptake surface area for N uptake and higher abscisic acid and cytokinin content in the medium and late growth stages (XIN et al., 2021XIN, W. et al. The Response of Grain Yield and Root Morphological and Physiological Traits to Nitrogen Levels in Paddy Rice. Frontiers in Plant Science, v.12, p.1826, 2021. Available from: <Available from: https://www.frontiersin.org/articles/10.3389/fpls.2021.713814/full >. Accessed: Oct. 02, 2021.
https://www.frontiersin.org/articles/10....
).

The NUE for irrigated rice cultivars is the target of studies in several places in the world, the genetic improvement, aims to explore genes of interest that contribute to the expression of the best use of N (ISLAM, 2019ISLAM, M. S. Sensing and Uptake of Nitrogen in Rice Plant: A Molecular View. Rice Science, v.26, n.6, p.343-355, 2019. Available from: <Available from: https://www.sciencedirect.com/science/article/pii/S1672630819300800 >. Accessed: Nov. 21, 2021.
https://www.sciencedirect.com/science/ar...
; WANG et al., 2018AN, N. et al. Agronomic and environmental causes of yield and nitrogen use efficiency gaps in Chinese rice farming systems. European Journal of Agronomy, v.93, p.40-49, 2018. Available from: <Available from: https://www.sciencedirect.com/science/article/pii/S1161030117301673 >. Accessed: Jan. 12, 2022.
https://www.sciencedirect.com/science/ar...
). Contrary to what was observed in this study, short maturation varieties can have rapid initial development and, under appropriate conditions of sowing time, can result in better yields (AKTER et al., 2019AKTER, B. et al. Morpho-physiological Basis of Yield Performance of Early Maturing Rice Varieties in Bangladesh. Annual Research & Review in Biology, v.32, n.5, p.1-13, 2019. Available from: <file:///C:/Users/filip/Downloads/30097-Article Text-56474-1-10-20190819.pdf>. Accessed: Oct. 10, 2021. ). In general, NUE and grain yield can be affected by several factors inherent to cultivars, such as application rate, plant density and light interception, which is also influenced by the plant’s morphological structure and irrigation (HOU et al., 2019HOU, W. et al. Nitrogen rate and plant density interaction enhances radiation interception, yield and nitrogen use efficiency of mechanically transplanted rice. Agriculture, Ecosystems & Environment, v.269, p.183-192, 2019. Available from: <Available from: https://www.sciencedirect.com/science/article/pii/S0167880918304249 >. Accessed: Jan. 08, 2022.
https://www.sciencedirect.com/science/ar...
).

Thus, this research makes possible to have a greater knowledge of the dynamics and response of short and medium cycle cultivars to nitrogen fertilization, thus assisting in a more efficient management of nitrogen with greater economic return and less potential damage to the environment.

CONCLUSION:

The medium cycle cultivar has a greater capacity to explore the environment due to the larger area of the root system and greater leaf area, which gives the greater capacity to explore the resources of the environment. Under N fertilization, the increase in leaf area and root system of the medium cycle cultivar is even greater than that of the short cycle cultivar.

The medium cycle cultivar demands less N per unit of total dry matter and impacts on greater Nitrogen Utilization Efficiency and Nitrogen Utilization Physiological Efficiency. Grain yield is similar in both cultivars with the expected increases in N. However, in absolute numbers the productivity in the medium cycle cultivar is higher because it has a greater capacity to exploit the resources of the environment.

ACKNOWLEDGEMENTS

This research was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brasil which awarded a scholarship to the first author.

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  • CR-2021-0584.R2

Edited by

Editors:

Leandro Souza da Silva (0000-0002-1636-6643)

Publication Dates

  • Publication in this collection
    27 May 2022
  • Date of issue
    2023

History

  • Received
    04 Aug 2021
  • Accepted
    28 Jan 2022
  • Reviewed
    18 Apr 2022
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