Partitioning of Organic Fertilizers in the Production of KaleAbstract
In the production of kale, nitrogen is one of the nutrients that the plant needs in greater quantity. Its application must be divided throughout the cycle, due to the loss by leaching. The objective of the research was to evaluate the effect of splitting organic fertilizers in topdressing on the production of kale. The experimental design was randomized blocks, with four replications, with seven treatments being evaluated in a 2 x 3 + 1 factorial scheme, the first factor was the fertilizers (castor bean cake and bokashi) and the second the application intervals (7; 14 and 21 days), in addition to the control without topdressing fertilization. The amount of each fertilizer was calculated to provide the same dose of N (40 kg ha-1) every 21 days. The following characteristics were evaluated: plant height (PH), stem diameter (SD), number of leaves per plant (NLP), leaf fresh matter mass (LFMM), leaf length at the beginning (LLB), middle (LLMe) and end (LLE) of the cycle and “SPAD” index. There was no interaction between the factors, for any characteristic evaluated. For all traits, the values observed in control was lower than treatments with topdressing. The increases of treatments of factorial in relation to the control were 37.8% (plant height); 31.8% (SD); 157.1% (NLP); 213.5% (MLFMM); 7.6% (LLB); 80.2% (LLMe) and 126.6% for the “SPAD” index. It is recommended to use castor bean cake and split it every 21 days as it results in less labor for application.
Keywords:
castor bean cake; bokashi; nitrogen; organic agriculture
HIGHLIGHTS
For kale production, the application interval in topdressing makes no difference.
It is recommended to use castor bean cake it every 21 days for kale topdressing.
It is possible to reduce labor in kale production, with less topdressing times.
INTRODUCTION
The vegetable species of the Brassicaceae family play an important role in human nutrition, with the genus Brassica being the most important, both for its economic and nutritional value and for its market acceptance, with emphasis on the species Brassica oleracea, which comprises several crops, such as cabbage (B. oleracea var. capitata), cauliflower (B. oleracea var. botrytis), broccoli (B. oleracea var. italica) and kale (B. oleracea var. acephala) [1; 2].
The consumption of kale has increased, especially among people who want to have a healthy diet, due to recent discoveries regarding the nutraceutical properties of the leaves. The kale contains a high water content, low lipid content, carbohydrates, is a rich source of glucosinolates that contribute to the elimination of toxins from the body and has a high content of flavonoids, ascorbic acid and anticarcinogenic action [1; 2; 3; 4]. The leaves are also considered a good source of calcium, potassium, magnesium and fiber [1; 4].
These changes in the agri-food sector are also due to the growing concern on the part of consumers and producers with the environment, which has increased production and demand for food produced in the organic system [2; 3]. Brassicas are among the main vegetables produced in this system, in which pesticides or inorganic fertilizers cannot be used to supply essential nutrients to the plants, requiring the use of sustainable practices such as green manure and organic fertilizers.
In the production of kale, one of the nutrients that the plant needs in greater quantity is nitrogen [2]. However, as it is easily leached in the soil, it is usually applied in installments with part at planting and part in topdressing, and there are no reports of research with organic fertilizers in topdressing in this crop. To meet the nutritional needs of plants, organic fertilizer must be able to provide nutrients at a speed similar to the demand of the crop. In this context, the proper management of organic fertilizers, through the division of the product, can provide greater efficiency in the use of nutrients by the plants and reduce labor costs.
As it has a long production cycle, it is recommended to divide the nitrogen throughout the entire kale cycle, with weekly applications. However, this recommendation is for inorganic, fast-release fertilizers. For organic fertilizers, because they release nutrients more slowly, perhaps the application can be more spaced, allowing a reduction in labor costs in the application.
One of the organic fertilizers most used by farmers in top dressing is castor bean cake [4; 5; 6; 7], which is a residue from the castor bean oil extraction industry. Another organic fertilizer that has been widely used is bokashi [8], which is the addition of efficient microorganisms that act in the fermentation of various materials, such as straw, manure and bran. Bokashi microorganisms decompose organic matter, transform and make nutrients available in soluble substances for plants [8].
The objective of this research was to evaluate the effect of splitting the organic fertilizers castor bean cake and bokashi in top dressing on the production of kale under organic management.
MATERIAL AND METHODS
The experiment was conducted at the Experimental Farm of São Manuel, School of Agriculture (FCA) - Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Botucatu, SP, located at 22º 44'28” S and 48º 34'37” WGr and altitude of 740 m. The region's climate, according to the Köppen classification, is mesothermal type Cfa, humid subtropical, with rainy summers and dry winters [9].
The soil in the area is classified as Typical Dystrophic Red Latosol and the crop that preceded the implementation of the experiment was corn. Before the installation of the experiment, soil was collected (0-20 cm) for chemical analysis, obtaining the following values: pH(CaCl2) = 5.8, organic matter = 13 g dm-3, Presin = 190 mg dm-3, V = 67%, Al3+ = 0 mmolc dm-3, H + Al = 11 mmolc dm-3, K = 3.5 mmolc dm-3, Ca = 12 mmolc dm-3, Mg = 7 mmolc dm-3, SB = 22 mmolc dm-3, CEC = 33 mmolc dm-3, S = 5 mg dm-3, B = 0.22 mg dm-3, Cu = 2.0 mg dm-3, Fe = mg dm-3, Mn = 5.8 mg dm-3 and Zn = 18.2 mg dm-3.
Seven treatments were evaluated in a 2 x 3 +1 factorial scheme, in which the first factor was the fertilizers used in topdressing (castor bean cake and bokashi) and the second was the application intervals (every 7; 14 and 21 days), in addition to the control without top dressing fertilization. The experimental design was randomized blocks, with four replications of 18 plants per plot. Before planting, only Provaso® organic compost was used. at a dose of 30 t ha-1 [10], which was incorporated into the total area. Chemical analyzes were carried out in all organic fertilizers used (Table 1). In top dressing, 6.3; 12.5 and 18.8 g per plant of castor bean cake were applied and 12.6; 25.1 and 37.7 g per plant of bokashi in treatments with application every 7, 14 and 21 days, respectively, aiming to provide the same amount of N per plant throughout the cycle.
The hybrid Hi-Crop (Takii) was used, and sowing was carried out in polypropylene trays with 162 cells, containing Carolina® substrate, with one plant per cell. The seedlings were transplanted into beds with spacing of 0.50 m between rows and 1.00 m between plants, totaling 18 plants per plot (3 rows with 6 plants each), but only the four central plants of each plot were evaluated.
The implantation and the cultural management followed the technical recommendations, according to [10] and [11] and the irrigation system used was sprinkler, applying an average of 3 mm of water per day.
At the end of the experiment cycle, the height (m) of the plants was evaluated with a measuring tape and the diameter of the stem (mm) with a caliper.
Harvests were performed every seven days, starting at 50 days after transplanting (DAT) and the last harvest was at 239 DAT. The leaves were harvested when they were between 20 and 30 cm in length and were considered for evaluation only the commercial leaves, without apparent defects. After each harvest, the following characteristics were evaluated: number and mass of the leaves (they were weighed in a scale with a precision of 0.1g). At the beginning (64 DAT), in the middle (119 DAT) and at the end (239 DAT) of the harvests, the length of the leaves (cm) was evaluated.
At 119 DAT, an evaluation of the relative chlorophyll index (“SPAD” index) was carried out with the indirect chlorophyll meter Minolta SPAD-502 (Soil Plant Analysis Development), carried out at three points per leaf, three leaves per plant, using the average of these to represent the value of each plot.
The experimental data were submitted to tests of normality and homogeneity of variance (Shapiro-Wilk). Then, analysis of variance and Tukey's test (p ≤ 0.05) were performed to compare the means of treatments, using the statistical software AgroEstat [12].
RESULTS AND DISCUSSION
For all variables analyzed, the values of the control without top dressing was lower than the treatments of the factorial, that is, with top dressing (Table 2), obtaining increases in the comparison between average of treatments with top dressing in relation to the control of 38%, 32%, 157%, 213% and 127% for plant height, stem diameter, number of leaves per plant, fresh mass of leaves per plant and SPAD index, respectively. For leaf length at the beginning and middle of the crop cycle, increases were 7.57% and 80.15%, respectively, while for the end of the cycle there was no comparison with the control because there were no leaves classified as marketable in the control.
These results confirm the importance of performing topdressing fertilization to increase kale yield, even more so with a cycle of 239 DAT, when the plant extracts a large amount of nutrients that are exported with the harvesting of the leaves. The application of fertilizers sources of nitrogen in top dressing is essential to increase the production of the plants [13], as this nutrient is easily lost by leaching.
An increase in the production of various vegetables has been observed with the use of castor bean cake or bokashi topdressing [6; 7; 14; 15; 16; 17; 18; 19], and this work confirms this need, even more so in a crop with a long production cycle. This increase occurs because the organic fertilizer is responsible for promoting soil protection, nutrition of microorganisms that mobilize nutrients and are sources of nutrients that are made available to plants throughout the cycle [4; 5].
For the final plant height (Table 2), when comparing the fertilizers, the treatment with castor bean cake was superior to that with bokashi only in the splitting every 7 days, with no difference between the fertilizers in the splitting every 14 and 21 days. For splitting within the fertilizers, the difference occurred in the castor bean cake, when the plants were fertilized every 21 days, the height was lower than with 7 or 14 days. The greater height of the plants in the treatment with castor bean cake split every 7 days, which could be an indication of excessive growth, occurred due to the greater development of the plants, with the production of a greater number of leaves compared to the use of bokashi (Table 2).
For stem diameter, treatments with application of castor bean cake resulted in higher values than the bokashi treatments in the 7 and 21 day splits (Table 2) and no differences were obtained with the 14-day split. For both castor bean cake and bokashi, the interval between applications did not affect stem diameter. [2] obtained an average stem diameter of 32 mm at 93 DAT using the same hybrid, a value similar to that obtained in the present research.
Plant height and stem diameter are characteristics related to plant vigor, easily measurable and non-destructive, and can be evaluated without harming other evaluations. Although the plants remained in the field for 239 DAT, they did not grow much, less than 40 cm, as this is a characteristic of the Hi Crop hybrid, which facilitates handling and staking the plants was not necessary.
For total number and fresh mass of leaves per plant and length of leaves in the middle and at the end of the productive cycle, the results were similar, with higher values in treatments with castor bean cake applied every 7 or 21 days and no difference to the bokashi with14-day interval (Table 2).
In research carried out by [5], it also reported greater production of fresh mass of the aerial part of jambu plants with the use of castor bean cake compared to the use of bokashi. In beetroot, It was observed by [8; 14], greater increases in productivity in relation to the control without fertilization in top dressing with castor bean cake compared to bokashi. Although the N dose was the same, the rate of nutrient release by organic fertilizers is different. Castor bean cake has a low carbon/nitrogen ratio (Table 1), which favors a faster release of nutrients. According to [19], castor bean cake is a material with high microbial activity, its decomposition is very fast, and the nutrients are more quickly released and utilized by the plants. Increased productivity has been reported with the use of castor bean cake top dressing in different vegetables, such as zucchini [4], jambu [5], beetroot [14], arugula [16] and cabbage [17].
For the two fertilizers, there was no difference between the application intervals for leaf number, leaf production (mass) and leaf length in the middle and end of the productive cycle (Table 2). The values obtained were much higher than those reported by [2], average of 53 leaves per plant and by [1], an average of 51 leaves per plant, probably due to the long harvest period (up to 239 DAT) compared to 93 DAT and 147 DAT in research by [2] and [1], respectively. Other factors also contributed to the observed differences, such as the genotype studied. [1] used the cultivar Georgia, which usually emits several lateral shoots that must be removed and compete with the leaves for nutrients and photoassimilates, while the hybrid Hi Crop does not emit lateral shoots and favors an increase in the production of leaves with commercial size, as reported by [2] who emphasized the need to look for genotypes with a low number of lateral shoots in order to increase the productive potential in kale.
For leaf length at the beginning of the harvest (64 DAT) there was no difference either in the comparison of the intervals for each fertilizer, or between the fertilizers in the intervals (Table 2). At the end of the cycle (239 DAT), the length of the leaves was greater for the castor cake than for bokashi in the intervals of 7 and 21 days (Table 2). The fact that there were no differences at the beginning of the harvests is because few fertilizations were applied in top dressing, while at the end of the cycle there was already time for the fertilizers to have an effect.
The “SPAD index value was higher in treatments with castor bean cake compared to bokashi, regardless of the application interval (Table 2). The “Spad” index may be indicative of nitrogen deficiency (or excess) and help in the management of nitrogen fertilization of some vegetables [2]. The higher values obtained for the ''Spad'' index in the treatments with castor bean cake is another indication that this fertilizer should provide a greater release of nutrients, mainly N, for the plants, resulting in leaves with a darker green pigmentation compared to the use from bokashi.
Studies with increasing applications of nitrogen and organic fertilizers in vegetables found increases in chlorophyll contents and/or “Spad” index values in plant leaves [20; 21]. The “Spad” index used provides an instantaneous and non-destructive reading of the leaf, being an alternative to evaluate plant nitrogen in real time due to the fact that there is a significant correlation between the intensity of the green color with the chlorophyll content with the concentration of N on the leaf [21; 22], since 70% of this nutrient contained in leaves is in chloroplasts participating in the synthesis and structure of chlorophyll molecules [23; 24]. The chlorophyll is the pigment that is involved in photosynthesis and is present in all plants, being one of the factors related to the photosynthetic efficiency of plants and, consequently, to their growth. There was not difference between splitting intervals for the “Spad” index, and it was not observed no visible nitrogen deficiency, as if the leaves were very deficient, they would have a lighter shade of green.
The supply of nutrients in top dressing through different forms of splitting can provide better use by plants in their stages of greater nutritional demand [7; 13; 15]. However, the excessive number of installments can increase the cost of labor. Considering that for the characteristics related to leaf production there was no difference between the intervals between fertilizations and in the only characteristic in which there was a difference, the longest interval (21 days) resulted in plants with lower height, which cannot be considered a disadvantage, it is recommended that top dressing fertilization be carried out in this longer interval, with a reduction in the number of applications and, consequently, the labor required to carry out top dressing fertilization.
CONCLUSION
It is recommended to use castor bean cake in top dressing and splits the application every 21 days for the production of kale in the organic system. Since there is no difference for the characteristics evaluated under the conditions of the experiment, fertilize every 21 days and reduce the labor involved in application.
REFERENCES
- 1 Alves TN, Echer MM, Sackser GAB, Black AV, Klosowski ES, Macedo Júnior EK, et al. Effects of consortiums with okra on the physical and chemical characteristics of the kale under organic management. BJD. 2020; 6(10): 79987-80001.
- 2 Nasser MD, Cardoso AII, Vieites RL, Nasser FACM, Furlaneto KA, Ramos JA, et al. Effects of organic compost, gypsum, and topdress sulfur rates on bioactive compounds and physicochemical characteristics of collard greens. Scientia Plena. 2020; 16(9): 1-10.
- 3 Alves TN, Echer MM, Coutinho PWR, Macedo Júnior EK, Klosowski ES, Sackser GAB, et al. Effects of consortiums with okra on the physical and chemical characteristics of the kale under organic management. BJD. 2020; 6(10): 79987-80001.
- 4 Lanna NBL, Bardiviesso EM, Tavares AEB, Silva PN de L, Nakada-Freitas PG, Noda SBH, et al. Castor bean cake in top-dressing application as a source of nitrogen on the production and quality of zucchini organic seeds. Biosci J. 2020; 36(Supplement 1):130-42.
- 5 Nordi NT, Cardoso AII, Alves TN, Moraes VP de, Carvalho JR de. Organic fertilization in top dressing in jambu production. Comun Sci. 2022; 13:e3827.
- 6 Azevedo DMP, Beltrão NEM. Castor bean agribusiness in Brazil. Brasília: Embrapa Information Technology, 2007. 506 p.
- 7 Silva PN, Lanna NB, Cardoso AI. Bokashi rates in topdressing in the beet production. REAN .2018; 5(1): 28-34.
- 8 Nordi NT, Alves TN, Cardoso AII, Moraes VP, Carvalho JR. Organic fertilization on dry mass production and nutrient accumulation in jambu plants. Res, Soc Dev. 2022; 11(8): e51611831164.
- 9 Alvares CA, Stape JL, Sentelhas PC, Gonçalves JLM, Sparovek G. Koppen's climate classification map for Brazil. Meteorologische Zeitschrift. 2014; 22 (6): 711-728.
- 10 Trani PE, Terra MM, Tecchio MA, Teixeira LAJ, Hanasiro J. Organic fertilizer for vegetables and fruit trees. IAC, 2013,1-16.
- 11 Filgueira FAR. New vegetable farming manual: modern agrotechnology in the production and marketing of vegetables.3ª ed. Viçosa, MG: UFV, 2008.
- 12 Barbosa JC, Maldonado Junior W. Agronomic Experimentation & AgroEstat - system for statistical analysis of agronomic trials. Jaboticabal: FCAV/UNESP, 2015.
- 13 Colombari LF, Lanna NB, Guimarães LR, Cardoso AII. Production and quality of carrot in function of split application of nitrogen doses in top dressing. Hortic Bras. 2018; 36(3):306-312.
- 14 Silva PN, Lanna NB, Cardoso AII. Beet production depending on rates of castor bean cake as topdressing. Hortic Bras. 2016; 34(3):416-421.
- 15 Cardoso AII, Oliveira JB, Lanna NB, Candian JS, Castro JLM. Sources and splitting of the organic fertilization in top dressing in cabbage production. Hortic Bras. 2020; 38(2):230-234.
- 16 Cruz LKA, Ruffino GM, Pelvine RA, Cardoso AII. Sources of organic fertilizers on arugula production. Rev Brasieleira Agroecol. 2021; 16(2):123-131.
- 17 Hounmenou GV, Candian JS, Inowe MA, Colombari LF, Cardoso AII, Magro FO. Cabbage production in function of castor bean cake doses in top dressing. Comun Sci. 2021; 12(e3453):1-5.
- 18 Alves TN, Cardoso AII, Carvalho JR, Nordi NT, Oliveira MMV, Silva ISS, et al. Jambu (Acmella oleracea [(l.) rk jansen]) production with the use of different organic fertilizers before planting and top dressing. Comun Sci. 2023; 15:1-20.
- 19 Severino LS, Costa FX, Macêdo Beltrão NE, Lucena AMA, Guimarães MM. Mineralization of castor bean cake, cattle manure and sugarcane bagasse estimated by microbial respiration. Rev. Bioterra. 2004; 5(1): 20-26, 2004.
- 20 Sediyama MAN, Santos IC, Lima PC. Growing vegetables in the organic system. Rev. Ceres. 2015; 61(7): 829-837.
- 21 Porto JS, Costa RQ, Rebouças TNH, Lemos OL, Luz JMQ, Amorim YF. Tomato plant growth and SPAD index in different nitrogen sources and levels. Sci Plena. 2014;10(11):110-203.
- 22 Coelho FS, Fontes PCR, Puiatti M, Neves JCL, Silva MCC. Nitrogen rate associated with yield of potato and leaf nitrogen indices. Rev. Bras. C. Sol. 2010; 34: 1175-1183.
- 23 Kurtz C, Pauletti V, de Menezes Júnior FOG, Mora C. Nitrogen for diagnosis by chlorophyll index and nitrate in sap for onion in direct seeding system. Rev. Thema. 2022; 21(1):92-114.
- 24 Hahn L, Paviani AC, Feltrim AL, Wamser AF, Rozane DE, Reis ARD. Nitrogen doses and nutritional diagnosis of virus-free garlic. Rev. Bras. C. Sol. 2020; 44:1-14.
