Resumo em Inglês:

ABSTRACT The estimate of the potential sugarcane productivity through agroclimatic models aids in the agricultural planning of the crops and the quantification of the yield for a given region. For these estimated values to be considered robust there is a need for validating the performance of such models in different areas and agricultural varieties. Hence, the aim of this study was to validate the Agro-Ecological Zone (AEZ) method with fifteen sugarcane varieties in the region of the Vale do São Patrício, state of Goiás, Brazil. We evaluated the data referring to the cane-plant (one-and-a-half-year sugarcane), as well as the first and second sugarcane ratoons (both with one-year cycles) in an irrigated and dry farming system. The productivities obtained in dry farming were corrected due to the occurrence of a water deficit in the crop. The results indicated that the AEZ method presented productivity estimates more satisfactory for the one-year cultivation cycles (ratoon cycles) for all varieties studied, with the model adjusting best to the CTC15 variety (RMSE = 8.70 t ha-1; MAE = 6.05 t ha-1; d = 0.99).

Resumo em Inglês:

ABSTRACT Deficient ventilation rates and airflow patterns in naturally ventilated greenhouses are the main causes for the generation of inadequate and heterogeneous thermal conditions inside this type of structure. In this research, a numerical study was developed using a two-dimensional computational fluid dynamics model validated in a Colombian greenhouse established under warm climate conditions (PG). The objective of the research was to evaluate the effect on natural ventilation generated by the coupling of two ventilation towers on the PG greenhouse, scenario called MPG. The results indicated that airflow patterns over the region where crops are established in MPG are between 25.9% and up to 142.5% faster compared to PG, which generates ventilation rates up to 57.3% higher in MPG, which is why the temperature distribution under this scenario is more homogeneous inside the structure and its average thermal differential with the outside environment does not exceed 1.1 °C.

Resumo em Inglês:

ABSTRACT The aim of this study was to evaluate the effects of cropping systems (single and twin-rows) and N fertilizer rates in the second top-dressing on the agronomic performance and relative economic returns of maize. The experiment was conducted in a randomized block design, with subplots and three repetitions. The plots were composed of two cropping systems: single and twin-rows. The subplots consisted of six rates of N fertilizer, applied in the second top-dressing fertilization in the V8 phenological stage (eight fully developed leaves) of maize: 0, 14, 28, 56, and 70 kg ha-1 of N. The first application of N top-dressing fertilization (rate of 140 kg ha-1 N) was during the V4 phenological stage (four fully developed leaves) in all treatments. The cropping system of twin-rows provides a higher grain yield and relative economic return of maize. The agronomic efficiency of the twin-row cropping system decreases with increasing N rates, but remains higher than that obtained in the single-row system, independent of the N fertilizer top-dressing rate.. The application of the second N top-dressing fertilization in the V8 phenological stage increases linearly with the grain yield and relative economic return of maize, independent of the cropping system.

Resumo em Inglês:

ABSTRACT The objective with the work was to evaluate, during storage, the rice seeds physical and physiological quality, cultivar IRGA 424 RI, dried with different drying air temperatures. For such, rice seeds were harvested with a moisture content of 22%. Then, they were subjected to drying in a cross-flow dryer, operating in an intermittent system and using the 55 and 65 ºC drying air temperatures. After, samples containing 50 kg of seeds were stored in PP Woven Bags for 240 days. After drying and every 60 days, physical and physiological analyses were performed. The experiment was conducted under a completely randomized design, arranged in a split-plot scheme, with 4 replications. The physical quality, estimated by the seed hectoliter weight, decreased during storage, regardless of the drying air temperature. The germination percentage, as well as the vigor increased during storage, regardless of drying air temperature due to the dormancy overcoming process. The dry seeds with the highest drying air temperature showed less vigor throughout the storage, according to the cold test. The rice seeds drying with an air temperature of 65 ºC, promoted a higher drying speed and did not negatively influence the seeds physical and physiological quality, however, reduced the vigor.

Resumo em Inglês:

ABSTRACT The search for techniques that maximize the use of water is becoming necessary for the sustainability of agriculture in semi-arid areas. In this sense, the present work aimed to evaluate the effects of soil protection against water loss and the use of bovine biofertilizer on fruit production and chlorophyll content in bell pepper plants. The experiment was conducted in the municipal district of Nova Floresta in the semi-arid region of the State of Paraíba during the period of August 2010 to February 2011. The experimental design was a randomized block design with four repetitions in a 2 × 2 × 2 factorial scheme, corresponding to soil without and with bovine biofertilizer, without and with mulch, and without and with side coating of the grooves with polyethylene film, to reduce water loss through evaporation and lateral movement of water. The results showed that the use of side coatings of the grooves led to greater production, generating productivity gains in bell pepper cultivation. The association between side coating of the grooves and mulching of the soil resulted in increased levels of chlorophyll, but the bovine biofertilizer × side coating × mulch interaction inhibited the production of chlorophyll in the plants.

Resumo em Inglês:

ABSTRACT Nitrogen fertilization, besides increasing productivity, can favor the production of well-formed, large, and heavy grains, which are traits valued by the oat processing industry. However, high nitrogen (N) doses may lead to plant lodging, which could be solved by using growth retardant. This study aimed to evaluate the industrial quality of white oat grains cultivated under different nitrogen doses and associated with the growth retardant trinexapac-ethyl in two growing environments. Experiments were conducted in Londrina and Mauá da Serra, PR, Brazil, using the cultivar IPR Afrodite in a randomized block design in a 4 × 2 factorial scheme and four replications. Treatments consisted of four topdressing N doses (0, 30, 60, and 90 kg ha−1) and the application or not of growth retardant. Thousand-grain weight, hectoliter weight, grain index greater than two millimeters, peeling index, and industrial grain yield were evaluated. The effect of N fertilization and growth retardant on the industrial quality of white oat grains depends on the characteristics of the growing environment. The trinexapac-ethyl application reduces grain quality in Londrina and Mauá da Serra. However, the industrial quality of grains is high in both growing environments when the growth retardant is associated with nitrogen doses.

Resumo em Inglês:

ABSTRACT Bowdichia virgilioides Kunth is a medium size tree used in folk medicine and in furniture manufacturing which makes it a target of extractive processes. The aim of this work was to evaluate the endogenous content of polyamines, amino acids, and sugars in seedlings of Bowdichia virgilioides that presented or not the development of spontaneously differentiated vegetative propagules in their roots. An average of thirty percent Bowdichia virgilioides in vitro growing plants cultivated in MS basal medium without growth regulators presented the differentiation of vegetative propagules. It was noted the propagules units presents embryo-like structures (globular - to leaf-shaped features) and these plants showed a compromised development when compared to the plants that do not presented these morphogenetic structures. Total sugars and amino acids content was significantly higher in the roots of plants with the vegetative propagules. With regard to polyamines content, there was no statistical difference, for spermine and spermidine. However, higher levels of putrescine were found in plants developing vegetative propagules. In this way, these results showed that this event are related to the amino acids, sugars and polyamines, mainly putrescine content.

Resumo em Inglês:

ABSTRACT Ear rot caused by fungi of genus Fusarium (FER) is one of the potentially harmful diseases to grain quality in maize. Given the capacity to produce mycotoxins, FER presents a risk to food safety. This study sought to identify parents and indicate hybrids of popcorn with a higher level of resistance to the incidence and severity of FER. Hybrids were produced from the crossing of 15 lines in S7 generation and 5 testers. The hybrids, together with the parents and five more genotypes used as control, were evaluated in a field trial. It was used a randomized block design arranged in 10 x 10 lattice. Data were submitted to analysis of variance by the F test (p < 0.05) and then by the mean grouping test of Scott Knott (p < 0.05). The results showed the possible to explore new sources of resistance to FER among germplasm evaluated. Both additive and non-additive gene effects are important in FER resistance. To obtain gains in FER resistance, the development of popcorn hybrids should consider the use of parental lines with low means of severity and good general combining ability.

Resumo em Inglês:

ABSTRACT Hass avocado production systems in Colombia have increased to become the third largest area planted for fruit production. A number of factors that limit productivity such as diseases have become of high economic importance. The objectives of this study were to identify the causal agents associated with pathologies in Hass avocado crops in different stages of development and to determine main environmental factors associated with their incidence. This work was conducted over a period of eight years (2009-2016), during which plots and nurseries were monitored. Results showed that the most common disease of Hass avocado was avocado wilt complex (AWC) caused mainly by Phytophthora cinnamomi. In addition, it was found that pathogens such as Lasiodiplodia theobromae, Colletotrichum gloeosporioides sensu lato, and Phytophthora palmivora, can affect diverse tissues of avocado plants, appearing in different stages of crop development. Incidence of different pathologies in commercial plots were influenced by technological level, the sampling season (rainy and dry), and environmental and topographical variables such as precipitation, slope and elevation. This work presented a holistic approach for analysis of pathologies in Hass avocado crops, which were determined by the stage of crop development, environmental and topographic variability and the technological level of the productive system.

Resumo em Inglês:

ABSTRACT Improved methods of weed control are required to support expansion of large-scale cowpea cultivation in mid-west Brazil. With the aim of testing our hypothesis that the tolerance of cowpea cultivars to sulfentrazone is dose- and genotype-dependent, we assessed the effects of increasing doses (0, 250, 500 and 1,000 g ha-1 of sulfentrazone) on the cultivars BRS Imponente, BRS Novaera, BRS Tumucumaque and BRS Itaim. The phytotoxic effects of sulfentrazone varied according to the dose of herbicide applied, although the symptoms were mild and only observable at the initial stages of development and at the highest dose tested. No statistically significant interactions were detected between cultivars and doses, and there were no significant differences between doses regarding population density, plant height, yield components and grain yield. Our results demonstrate that sulfentrazone is highly selective and can be applied to the studied cultivars without affecting growth or yield.