RESUMO O cultivo do amendoim tem importância nacional e global na agricultura e na indústria. Em condições limitadas de água, sua produtividade diminui ao ponto de comprometer o sucesso da exploração. Este estudo teve como objetivo avaliar o rendimento da cultura do amendoim e seus componentes de produção sob irrigação plena e deficitária aplicada na fase reprodutiva, para determinar o impacto do fornecimento de água no rendimento do amendoim cultivado na segunda época no Estado de São Paulo, Brasil. O experimento foi conduzido durante dois anos e seguiu um delineamento de blocos ao acaso com cinco níveis de irrigação distribuídos em faixas, com quatro repetições. Os tratamentos consistiram na reposição da evapotranspiração da cultura de 100 a 10%. No primeiro ano, sob temperaturas adequadas, o rendimento máximo atingiu 3.922 kg ha-1 com a aplicação de uma lâmina de irrigação de 277 mm e diminuiu em até 35% com a menor lâmina (48 mm). No segundo ano, temperaturas subótimas causaram atraso no ciclo de crescimento e casou redução de 33% na produtividade da cultura. Apesar dos potenciais benefícios da irrigação deficitária no aumento da produtividade da água, as baixas temperaturas representam um risco para o rendimento do amendoim na segunda safra. indústria exploração reprodutiva Paulo Brasil faixas repetições 10 10% ano adequadas 3922 3 922 3.92 ha1 ha 1 ha- 27 35 48 (4 mm. . mm) 33 safra 392 92 3.9 2 4 ( 39 9 3.

ABSTRACT Peanut cultivation has national and global significance in agriculture and industry. Under water-limited conditions, its yield decreases to the extent that it compromises the success of the exploitation. This study focused on evaluating peanut crop yield and production components under full and deficit irrigation applied in the reproductive phase, to determine the impact of water supply on the yield of peanuts grown in the off-season in the State of São Paulo, Brazil. The experiment was conducted for two years and followed a randomized blocks design with five irrigation levels distributed in strips, with four repetitions. The treatments consisted of crop evapotranspiration replenishments from 100 to 10%. In the first year, under suitable temperatures, the maximum yield reached 3,922 kg ha-1 with the application of 277 mm of irrigation depth and decreased up to 35% with the lowest irrigation depth (48 mm). In the second year, suboptimal temperatures caused a delay in the growing cycle and caused a 33% reduction in crop yields. Despite the potential benefits of deficit irrigation in increasing water productivity, low temperatures pose a risk to peanut yield, especially during the off-season crop in the region. industry waterlimited limited conditions exploitation phase offseason off season Paulo Brazil strips repetitions 10 10% year 3922 3 922 3,92 ha1 ha 1 ha- 27 35 48 (4 mm. . mm) 33 yields productivity region 392 92 3,9 2 4 ( 39 9 3,

ABSTRACT Sugarcane is grown in several countries and environmental conditions, and production increases should not only be based on the expansion of the cultivated area. As water is a limiting factor for sugarcane yield, irrigation is crucial to increase its yields. Thus, this study aimed to evaluate the agronomic performance of five sugarcane cultivars under irrigated and rainfed conditions and compare yields in each treatment with those of previous cycles. The experiment was carried out from July 2017 to July 2018, which stands for the fourth sugarcane harvest. It consisted of two irrigation factors (irrigated and rainfed conditions), and five sugarcane cultivars (CTC4, IACSP93-3046, RB86-7515, IACSP95-5000, and IAC91-1099). Irrigation was applied to supply 100% of crop evapotranspiration. Irrigation increased sugarcane yields, and such increases varied with the genotype and crop cycle evaluated. In general, the cultivars most responsive to irrigation were IACSP93-3046 and IACSP95-5000, regardless of the evaluation cycle, and CTC4 from the fourth harvest onwards. Irrigation did not interfere with sugarcane technological quality if harvested after the middle of the crop season (June). Cultivars with higher tillering capacity, such as CTC4, had improved yield stability throughout the cycle when under irrigated conditions.

RESUMO A couve é uma hortaliça muito consumida no Brasil. No entanto, a qualidade e a produção desta hortaliça dependem da oferta e da qualidade da água, e o estresse hídrico, o salino, ou ambos podem inviabilizar seu cultivo. Objetivou-se avaliar o desempenho das características morfofisiológicas da couve cv. Geórgia sob níveis de irrigação e índices salinos após a primeira desfolha. O experimento foi conduzido em delineamento de blocos ao acaso, com tratamentos constituídos de combinações de valores de cinco níveis de condutividade elétrica da água (CEi, em dS m-1: C1 =0,80; C2 =1,30; C3 = 1,80; C4 = 2,30; C5 = 2,80) e quatro níveis de irrigação, baseado na capacidade do vaso (PwC: L1 = 55%; L2 = 70%; L3 = 85%; L4 = 100%), com quatro repetições. A altura de plantas, o diâmetro do caule e o número de folhas foram diretamente afetados pelas combinações de altas salinidades na água de irrigação. Já o índice de cor verde teve maior efeito negativo ocasionado pelos tratamentos na primeira avaliação. Para peso de matéria fresca e seca, e área foliar, o tratamento T16 (Condutividade 2,30 dSm-1 + nível de irrigação 100% da capacidade de água do vaso) apresentou o melhor resultado (206,67 g; 25,46 g; 3044 cm2, respectivamente). Já para eficiência do uso da água o tratamento T3 (Condutividade 0,80 dSm-1 + nível de irrigação 85% da capacidade de água do vaso) (22,95 g L-1) obteve melhor resultado. Os níveis de condutividade elétrica da água atrelados aos níveis de irrigação tiveram efeito direto sobre as características morfofisiológicas da couve.

ABSTRACT Collard is a vegetable widely consumed in Brazil. However, the quality and production of this vegetable depend on the supply and quality of water. Water stress and saline stress can make it impossible to grow. The objective of this study was to evaluate the performance of morphophysiological characteristics of collard cv. Georgia under irrigation levels and saline indices after the first defoliation.The experiment was conducted in a greenhouse, under random blocks design, and the treatments consisted of combinations of five water electrical conductivities (CEi in dS m-1: C1 =0.80; C2 =1.30; C3 = 1.80; C4 = 2.30; C5 = 2.80) and four irrigation levels based on the vase capacity (PwC: L1 = 55%; L2 = 70%; L3 = 85%; L4 = 100%), with four replications. Plant height, stem diameter and number of leaves were directly affected by combinations of high salinity levels in irrigation water. On the other hand, the green color index had a higher negative effect caused by the treatments in the first evaluation. For fresh and dry matter weight, and leaf area, T16 treatment (Conductivity 2,30 dSm-1 + irrigation level 100% vase water capacity) presented the best result (206.67 g; 25.46 g; 3044 cm2, respectively), while for water use efficiency, T3 treatment (Conductivity 0,80 dSm-1 + irrigation level 85% vase water capacity) (22.95 g L-1) gave better results. The water electrical conductivities linked to irrigation levels had a direct effect on the morphophysiological characteristics of collard.

ABSTRACT The response of biomass flow components of forage from the interaction between fertigation with wastewater and cutting height during the year is little known. The objective of this work was to verify the responses of morphogenic and structural characteristics of Urochloa brizantha as a function of fertigation application strategies with sewage treatment plant effluent (TSE), complemented with urea (U), associated with harvest with two plant heights during the dry and rainy periods. The forage cutting heights were 30 cm (H1) and 40 cm (H2), and nitrogen fertilization doses were 9.1 (D1), 12.1 (D2), 22.5 (D3), 26.6 (D4), and 34.0 (D5) kg of N per Mg−1 of dry matter (DM) produced, applied by TSE via fertigation, plus 7.5 kg N per Mg−1 of DM produced, applied in the form of urea by cover in all treatments. Factor analyses for the dry and rainy periods identified two processes that correspond to forage mass growth and leaf development. Analysis of variance showed that treatments D5H2 and D5H1 presented superior responses over the other treatments, in the dry, and rainy periods. The treatment D5H2 stood out in the process of forage mass growth, and D5H1 in leaf development.

ABSTRACT Brazil stands out worldwide for its high grain production in areas of direct sowing. The objective of this study was to simulate and assess the relationship of soil organic carbon content and nitrogen, crop yield, and biomass of two crop sequences under the no-tillage system in a subtropical region of São Paulo, Brazil, using CSM-CROPGRO-Soybean and CSM-CERES-Maize models. The modeling was carried out considering the meteorological conditions of Jaboticabal, SP, Brazil. The treatments consisted of combining two summer crops (maize and soybean) with maize cultivation as a winter crop. The average biomass and productivity for corn were 15594 kg ha−1 and 5996 kg ha−1, respectively, and for soybeans they were 5905 kg ha−1 and 3441 kg ha−1, respectively. For soil organic carbon and nitrogen, a small variation was observed between years, and in addition there was a decline in their levels after a year with low biomass production. In our study, the RMSE and MAPE values between the observed and simulated productivity by the model were 2.21 kg ha−1 and 44.24%, respectively. The analysis of main components for the cultivation of corn explained 83.9% of the variability, and for the cultivation of soy, 93.5%. Among the tested models, the CROPGRO was the one with the best accuracy.

RESUMO Aumentar a produtividade da batateira economizando recursos naturais é um desafio de todos os envolvidos na cadeia produtiva da batata. Foi realizado um experimento de campo com o objetivo de avaliar o efeito de diferentes níveis de fertilização, massa de tubérculos sementes e regime hídrico sobre a produção de batata cv. Orchestra. Os tratamentos testados foram forma de fertilização (F1= adubação convencional; F2= fertirrigação de acordo com a marcha de absorção da cultura; F3= fertirrigação parcelada em 3 vezes), massa de tubérculo semente (TS1= <50 g; TS2= >50 g), regimes hídricos [RH1= 50%; RH2= 100% de reposição da evapotranspiração de cultura (ETc)]. O estudo foi conduzido no delineamento em blocos casualizados, em parcelas subdivididas com fertilizações na parcela e massa de tubérculos sementes na subparcela, com seis repetições. Maior produtividade (48,18 t ha-1) e batata graúda (43,67 t ha-1) foram obtidas no tratamento fertirrigação (marcha de absorção) e massas de tubérculos sementes >50 g (48,61 e 42,78 t ha-1) no regime hídrico 100% ETc. Porém não houve diferenças nos fatores fertilização e massa de tubérculos sementes para as plantas submetidas ao regime 50% ETc para a variável produtividade de tubérculos (P>0,05). Maior eficiência do uso da água é atribuída ao RH1 50% ETc para tubérculos sementes maiores que 50 g de 39,82 kg m-3 de água. A maior razão de cobertura é atribuída a tubérculos sob regime 100% ETc e duração do ciclo de 89 dias. A forma de fertilização e massa de tubérculos sementes que influenciaram positivamente as variáveis estudadas foram a fertirrigação de acordo com a marcha de absorção da cultura e massas de tubérculos sementes >50 g para as duas condições hídricas (100% e 50% ETc).

ABSTRACT Increasing potato yield while saving natural resources is a challenge for all those involved in the potato production chain. A field experiment was carried out in order to evaluate the effect of different levels of fertilization, mass of seed tubers and the water regime on the production of potato cv. Orchestra. We tested fertilization methods (F1= conventional fertilization; F2= fertigation according to the rate of absorption by the crop; F3= fertigation split into 3 applications), seed tuber mass (ST1= <50 g; ST2= >50 g), and water regimes [WR1= 50%; WR2= 100% replacement of crop evapotranspiration (ETc)]. The study was conducted using a split-plot randomized block design, with fertilizers in the plot and seed tuber mass in the subplot, with six replications. The highest tuber yields (48.18 t ha-1) and greatest potatoes (43.67 t ha-1) were obtained in the treatment F2 and for seed tuber masses >50 g (48.61 and 42.78 t ha-1) under 100% ETc water regime. However, for plants subjected to 50% ETc, the factors fertilization and seed tuber mass caused no difference in tuber yield (P>0.05). The highest water use efficiency (39.82 kg m-3 of water) was found under WR of 50% ETc for seed tuber masses >50 g. The highest cover ratio was obtained with tubers under 100% ETc being 89 days the cycle duration. The fertilization method and seed tuber mass that positively influenced the studied variables were fertigation according to the culture absorption rate and seed tuber masses >50 g for both water conditions (100% and 50% ETc).

RESUMO A calibração de modelos é fator fundamental para a obtenção de elevadas acurácias na estimativa do crescimento e rendimento das culturas. Este estudo teve como objetivo parametrizar os coeficientes genético e de ecotipo do modelo DSSAT/Canegro para cinco cultivares de cana-de-açúcar mantidas sob três manejos hídricos, além de avaliar a precisão do modelo na estimativa da produtividade de colmos, produtividade de açúcar e altura de colmos. Foram utilizados dados experimentais de campo obtidos em dois anos de cultivo (2016 e 2017) na FCAV/Universidade Estadual Paulista, Jaboticabal, SP. As cultivares foram mantidas sob irrigação suplementar, irrigação deficitária e não irrigadas. Foram utilizados os dados do tratamento de irrigação suplementar (sem estresse) para a parametrização de cada cultivar. A acurácia do modelo foi verificada pela correlação de Pearson (r), raiz do erro quadrático médio (RMSE), erro médio (MBE), índice de concordância (d) e coeficiente de confiança (c). O modelo DSSAT/Canegro apresenta elevada acurácia na predição da produtividade de colmos e de açúcar da cana-de-açúcar cultivada sob regimes hídricos, apresentando-se como alternativa viável na simulação do rendimento da cultura. Para melhor performance do modelo DSSAT/Canegro, é necessário a parametrização das variáveis relacionadas ao ecotipo das cultivares, além dos coeficientes específicos das cultivares.

ABSTRACT Model calibration is a fundamental factor to obtain high accuracy in the estimation of crop growth and yield. This study aimed to parameterize the genetic and ecotype coefficients of the DSSAT/Canegro model for five sugarcane cultivars kept under three water managements, besides evaluating the accuracy of the model in predicting sugarcane stalk yield, sugar yield and height. Experimental field data were obtained from two years (2016 and 2017) of cultivation at FCAV/Universidade Estadual Paulista, Jaboticabal, SP, Brazil. The cultivars were maintained under supplementary irrigation, deficit irrigation and no irrigation. Data of the supplementary irrigation treatment (without stress) were used for the parameterization of each cultivar. Model accuracy was assessed by Pearson correlation (r), root mean squared error (RMSE), mean bias error (MBE), index of agreement (d) and confidence coefficient (c). The DSSAT/Canegro model is highly accurate in predicting stalk and sugar yields of sugarcane grown under water regimes, presenting itself as a viable alternative in sugarcane yield simulation. For better performance of the DSSAT/Canegro model, it is necessary to parameterize the variables related to the ecotype of the cultivars, besides the specific coefficients of the cultivars.

RESUMO A cultura do manjericão (Ocimum basilicum) é de grande importância para o comércio como condimento fresco ou seco, para consumo humano e óleo essencial para as indústrias farmacêutica e cosmética. Os excessos e déficits de água podem afetar a produção de biomassa das plantas, tornando necessário o uso da quantidade correta de água para cada cultura. Considerando que as determinações do consumo de água e dos coeficientes de cultivo para plantas medicinais são escassas, o objetivo deste estudo foi determinar a evapotranspiração e os coeficientes de cultivo de manjericão usando lisímetros. A evapotranspiração da cultura foi determinada por lisímetros de pesagem para as reposições de 100, 75 e 50% da evapotranspiração máxima diária. A evapotranspiração de referência da cultura foi estimada pela equação de Penman-Monteith. A evapotranspiração das culturas para o ciclo de 49 dias foi de 471, 352 e 236 mm, e as taxas diárias variaram de 4,8 a 9,4; 4 a 8,1 e 3,7 a 7,4 mm/dia, para as reposições de 100, 75 e 50% da evapotranspiração máxima diária. Os coeficientes de cultivo variaram de 1,5 a 2,8 e foram relacionados aos dias após o transplante, índice de área foliar, razão de cobertura e graus-dia acumulados.

ABSTRACT The basil (Ocimum basilicum) crop is of great importance for trading as fresh or dried condiment for human consumption and essential oil for pharmaceutical and cosmetic industries. Water excesses and deficits can affect biomass production of plants, making it necessary to use the correct amount of water for each crop. Considering that determinations of water consumption and cultivation coefficients for medicinal plants are scarce, the aim of this study was determining evapotranspiration and crop coefficients of basil using lysimeters. The crop evapotranspiration was determined by weighing lysimeters for the replacements of 100, 75 and 50% of the maximum daily evapotranspiration. The reference crop evapotranspiration was estimated by the Penman-Monteith equation. Crop evapotranspiration for the 49 day cycle was 471, 352 and 236 mm, and daily rates ranged from 4.8 to 9.4; 4 to 8.1 and 3.7 to 7.4 mm/day, for the replacements of 100, 75 and 50% of the maximum daily evapotranspiration. Crop coefficients varied from 1.5 to 2.8 and were related to the days after transplanting, leaf area index, cover ratio and cumulative degrees-day.

RESUMO Técnicas inovadoras que busquem minimizar os custos de produção e a onerosidade de determinadas operações são um dos grandes desafios atualmente no setor sucroenergético. Nesse sentido, objetivou-se estimar os valores do Pol do caldo da cana-de-açúcar, em função do °Brix e do peso do bolo úmido (PBU), utilizando modelagem por redes neurais artificiais (RNAs). Foi organizado um banco de dados constituído de 204 análises tecnológicas provenientes de um experimento de campo com 15 tratamentos e 2 anos de avaliação. Foram utilizados 75% dos dados para a calibração do modelo e 25% para a validação. Foram utilizadas RNAs do tipo Multilayer Perceptron para calibração e validação dos dados. Antes da calibração, as variáveis foram normalizadas. O algoritmo de treinamento utilizado foi o backpropagation e a função de ativação foi a sigmoide. As RNAs foram estabelecidas com duas camadas ocultas e o número de neurônios variando de 4 a 20 em cada. As 15 RNAs com menor raiz do erro quadrático médio foram apresentadas aleatoriamente pelo software, dentre as quais 6 foram escolhidas para verificação da acurácia. As RNAs apresentaram elevada acurácia para a estimativa do Pol do caldo da cana-de-açúcar, tanto na fase de calibração (R2 = 0,948; RMSE = 0,36%) quanto na validação (R2 = 0,878; RMSE = 0,41%), podendo ser alternativa viável ao método padrão de análise. Redes mais simples podem ser treinadas para apresentarem a mesma acurácia que redes mais complexas.

ABSTRACT Innovative techniques that seek to minimize the costs of production and the laboriousness of certain operations are one of the great challenges in the sugar-energy sector nowadays. Thus, the objective of the present study was to estimate the Pol values of sugarcane juice as a function of °Brix and wet cake weight (WCW) using artificial neural network (ANN) modeling. A database was organized consisting of 204 technological analyses from a field experiment with 15 treatments and 2 years of evaluation. 75% of the data were used for the calibration of the model and 25% for its validation. Multilayer Perceptron ANNs were used for calibration and validation of the data. Before calibration, the variables were normalized. The training algorithm used was backpropagation and the activation function was the sigmoid. The ANNs were established with two hidden layers and the number of neurons ranging from 4 to 20 in each. The 15 ANNs with the lowest root mean square errors were randomly presented by the software, among which 6 were chosen to verify the accuracy. The ANNs had a high accuracy in the estimation of sugarcane juice Pol, both in the calibration phase (R2 = 0.948, RMSE = 0.36%) and in the validation (R2 = 0.878, RMSE = 0.41%), and can replace the standard method of analysis. Simpler networks can be trained to have the same accuracy as more complex networks.

Abstract Sugarcane pre-sprouted plantlets (PSP) production system is an innovative method to enhance crop multiplication rate. Determination of crop evapotranspiration (ETc) is crucial for water requirement identification throughout the plant cycle for irrigation management. ETc can be satisfactorily measured by weighing lysimeters. The objective of the study was to construct and calibrate three low-cost weighing lysimeters to measure ETc of PSP. The built lysimeters had 0.6909 m2 area (1179 mm × 586 mm), with 400 mm depth supported by 3 load cells. Lysimeters calibration showed excellent precision measurements, due to high linear correlation (R2 = 1.0000) between electric signal and equivalent mass, high accuracy, confirmed by mean absolute error between 0.0272 and 0.0382 mm, mean square error between 0.0011 and 0.0024 mm2 and Willmott's index of agreement (d) equal to unit. Maximum hysteresis (0.1951 mm) and hysteresis at full scale (0.4492%) did not compromise the evaluations. Daily ETc measurements showed variation of 0.27 mm among lysimeters and were coincident with daily course of reference evapotranspiration (ETo). The cost of the equipment was low, except for the data acquisition system. Therefore, lysimeters presented low cost and were adequate to measure ETc of PSP in greenhouse-grown.

ABSTRACT Through the use of remote sensing, the productivity and the nutritional state of the plants can be estimated in relation to the nitrogen doses due to the modification of the canopy reflectance. In this study, values of the normalized difference vegetation index (NDVI) obtained by a terrestrial optical sensor were correlated with productivity and contents of nitrogen (N) and of foliar crude protein (CP) of Brachiaria brizantha cv. Marandu, fertigated with doses of sewage treatment effluent (STE) The NDVI average rates of the forage were obtained by the active terrestrial sensor (GreenSeeker) before the harvests that were realized every 28 days in 2014. Five fertigated treatments with the following fractions of STE in water were evaluated: E5 = 1.0; E4 = 0.87; E3 = 0.60; E2 = 0.31; and E1 = 0.11. During the 12 months of experiment, the treatment E5 received 1,132 kg ha-1 of N and the others received quantities proportional according to the application fractions defined in each treatment. The increasing application doses of STE resulted in higher yields of dry biomass and better leaf qualities in N and crude protein (CP). The productivity, the foliar N content and the NDVI index were increasing due to the gradual application of applied STE. There was a high linear correlation among the NDVI indexes and the productivity (r>0.9256) and with the N content (r>0.9570) and also for CP (r>0.8421) and leaf N (r>0.8339), demonstrating that the method can be used to estimate forage productivity and quality.

RESUMO Objetivou-se, neste trabalho, avaliar o desempenho de três modelos de gotejadores de fluxo normal utilizando não apenas o efluente de esgoto tratado puro e diluído mas também dois tipos de filtro, tela e disco. O efluente de esgoto tratado utilizado no experimento foi proveniente da estação de tratamento da cidade. Esta unidade experimental foi composta por 12 linhas laterais com três modelos de gotejadores, dois modelos de filtro e se utilizou, como água de irrigação, o efluente de esgoto tratado puro (100%) e diluído em água (50%). Para cada modelo de gotejador foram definidos os tratamentos, sendo: T1 (efluente diluído em 50% com água subterrânea e uso de filtro de tela); T2 (efluente diluído em 50% com água subterrânea e uso de filtro de disco); T3 (efluente 100% e uso de filtro de tela); T4 (efluente 100% e uso de filtro de disco). Os resultados permitem afirmar que há modelos de gotejadores menos susceptíveis ao entupimento, sendo o gotejador de pastilha menos sensível ao entupimento. O filtro de disco é o mais indicado para prevenir o entupimento. O uso de efluente de esgoto puro ou diluído aumenta o coeficiente de variação de vazão dos gotejadores.

ABSTRACT The objective of this study was to evaluate the performance of three models of drippers using treated sewage effluent, pure and diluted, and two types of filters, screen and disc. The treated sewage effluent used in the experiment was collected from the city’s treatment plant. The experiment included 12 lateral lines with three types of emitters to apply pure (100%) and diluted (50%) effluent filtered by screen and disc filters. The combination of those factors set the treatments: T1 (50% effluent diluted in fresh water filtered by a screen filter); T2 (50% effluent diluted in fresh water filtered by a disc filter); T3 (pure effluent filtered by a screen filter); T4 (pure effluent filtered by a disc filter). The results showed that the flat type emitter is less sensitive to clogging, the disc filter is the most suitable to prevent clogging and the use of pure or diluted sewage effluent increases the drippers’ flow rate coefficient of variation.

ABSTRACT: Simulation models of crop growth enable estimating crop yield and water balance components with low cost and high precision. This study aimed to calibrate and evaluate the performance of the CS-CROPGRO model for common beans under the conditions of Jaboticabal city (SP), Brazil. The model was calibrated and tested with data previously collected from two experiments conducted in 2002 and 2003. In these experiments, treatments corresponded to two irrigation scheduling methods (tensiometers and class A pan evaporation) and two cropping systems (conventional and no-till). For calibration, data from the experiment carried out in 2002 were used. For testing, we used data from the experiment conducted in 2003. By using the genetic coefficients calibrated for cultivar IAC-Carioca, the model could correctly simulate phenology, leaf area, dry matter and grain yield during both, calibration and testing, under no-till and conventional systems, combined with tensiometer and class A pan irrigation scheduling methods. Conversely, the model did not show the same performance for soil moisture simulations.

RESUMO Um dos fatores que determinam os baixos índices zootécnicos na pecuária brasileira é a estacionalidade da produção das plantas forrageiras tropicais. A irrigação pode proporcionar aumento e estabilização da produtividade durante o outono e o inverno. Objetivou-se pelo presente estudo avaliar: a) a produtividade de massa seca e qualidade de forragem de Brachiaria brizantha, em função de lâminas de irrigação, no período do outono e do inverno; b) a umidade do solo e a temperatura do ar a fim de determinar seus efeitos na produtividade de forragem. O experimento foi conduzido na Fazenda Experimental da FCAV-Unesp, em Jaboticabal-SP. Utilizou-se de um sistema de aspersão em linha para estabelecer tratamentos com cinco lâminas de irrigação correspondentes a frações da evapotranspiração de referência (L1= 0,18; L2= 0,52; L3= 1,00; L4= 1,45 e L5= 1,67), em duas estações do ano: outono e inverno. A produtividade de forragem foi mais elevada no outono, e a resposta de produtividade à lâmina de água foi ajustada por uma função quadrática, atingindo produtividades máximas com lâminas de 267 e 269 mm para o outono e o inverno, respectivamente. Alto valor nutritivo da forragem foi obtido em ambas as estações do ano, com incrementos nos teores de proteína bruta com acréscimo da lâmina de irrigação somente no outono. As lâminas de água não afetaram os teores de fibra detergente neutro da forragem.

ABSTRACT One of the reasons of low performance of the Brazilian livestock industry include the seasonal growth of tropical pasture grasses. Irrigated grasslands may have higher and most stable rates of yield during autumn and winter seasons. Therefore, we aimed at evaluating: a) Brachiaria brizantha dry matter yield and forage quality as a function of different water depths during the autumn and winter, and b) soil moisture and air temperature effects on forage yield. The experiment was carried out at the Experimental Farm of the University of São Paulo State (FCAV – UNESP), campus in Jaboticabal – SP, Brazil. We used a line-source sprinkler system to provide five levels of irrigation (L1= 0.18, L2= 0.52, L3= 1.00, L4= 1.45, and L5= 1.67). These water depths corresponded to fractions of reference evapotranspiration in both autumn and winter. Forage yield was higher in autumn and water depth responses were fitted by a quadratic function, reaching maximum values at 267 and 269 mm during autumn and winter, respectively. During the autumn, we observed a highly nutritive forage with crude protein increment by increasing water depths. However, water application had no effect on neutral detergent fiber content.

O presente estudo foi realizado no Instituto Agronômico do Paraná (IAPAR), em Londrina, Estado do Paraná (latitude de 23º18'S, longitude de 51º09'W e altitude média de 585 m). O clima local, segundo a classificação do Köppen, é do tipo Cfa, ou seja, subtropical úmido, com chuvas em todas as estações, podendo ocorrer secas no período de inverno. Determinou-se a evaporação (E) da água do solo sob diferentes densidades de cobertura com resíduo da cultura de trigo. Os tratamentos foram instalados em lisímetros de pesagem de 2,66 m² e 1,3 m de profundidade, que permitem determinar E por diferença de massa com precisão equivalente a 0,1 mm em intervalos de uma hora. Os tratamentos consistiram em 0; 2,5; 5 e 10 t ha-1 de resíduos da cultura do trigo, colocadas de forma homogênea em cada lisímetro. No primeiro ciclo (22/09 a 20/10/2008), a redução de E em relação ao solo descoberto foi de 4; 15 e 24%, enquanto no segundo ciclo (01/12 a 30/12/2008), a redução foi de 15; 22 e 25%, respectivamente, para os tratamentos 2,5; 5 e 10 t ha-1.

This study was conducted at the Agronomic Institute of Paraná (IAPAR) in Londrina, State of Paraná (PR), Brazil (latitude 23º18'S, longitude 51º09'W and average altitude of 585 m). The local climate, according to the classification of Köeppen, is Cfa type, i.e., humid subtropical climate, with rain in all seasons and can occur dry seasons during the winter. It was determined soil evaporation (E) under different coverage densities with residue from the wheat crop. The treatments were installed in weighting lysimeters of 2.66 m² and 1.3 m deep, which allows to determine E by the mass difference with measuring precision of 0.1mm at one hour intervals. Treatments consisted of 0; 2.5; 5 and 10 t ha-1 of wheat crop residues, placed evenly over each lysimeter. In the first cycle (September 22nd to October 20th, 2008), the reduction of E, as compared to a bare soil, was 4; 15 and 24%, while in the second cycle (December 1st to 30th, 2008), the reduction was of 15; 22 and 25%, respectively, for the treatments of 2.5; 5 and 10 t ha-1.