BACKGROUND: We evaluated different machine learning (ML) models for predicting soybean productivity up to 1 month in advance for the Matopiba agricultural frontier (States of Maranhão, Tocantins, Piauí, and Bahia). We collected meteorological data on the NASA-POWER platform and soybean yield on the SIDRA/IBGE base between 2008 and 2017. The ML models evaluated were random forest (RF), artificial neural networks, radial base support vector machines (SVM_RBF), linear model and polynomial regression. To assess the performance of the models, cross-validation was used, obtaining the value of precision by R 2 , accuracy by root mean square error (RMSE), and trend by the mean error of the estimate (EME). RESULTS:The results showed that the RF algorithm achieves the highest precision and accuracy, with R 2 of 0.81, RMSE of 176.93 kg ha −1 and trend (EME) of 1.99 kg ha −1 . On the other hand, the SVM_RBF algorithm showed the lowest performance, with R 2 of 0.74, RMSE of 213.58 kg ha −1 and EME of −15.06 kg ha −1 . The average yield values predicted by the models were within the expected range for the region, which has a historical average value of 2.730 kg ha −1 . CONCLUSION: All models had acceptable precision, accuracy and trend indices, which makes it possible to use all algorithms to be applied in the prediction of soybean crop yield, observing the particularities of the region to be studied, in addition to being a useful tool for agricultural planning and decision making in soy-producing regions such as the Brazilian Cerrado.

The objective of this study was to analyze the variations of the decoupling factor and the aerodynamic and stomatal conductances for cowpea subjected to different levels of water availability during the reproductive phenological stages of the crop. The study was conducted in the municipality of Castanhal located in the northeast of the state of Pará, Brazil, in an area planted with cowpea, in 2013, 2014 and 2015 with four irrigation treatments: T100 - replacement of 100% of the crop evapotranspiration (ETc); T50 - replacement of 50% ETc; T25 - replacement of 25% ETc; and T0 - without any replacement (without irrigation). The interaction between the crop and the atmosphere in water vapor exchange was estimated through the decoupling factor (Ω), which was between 0.5 and 1, except for the treatment without irrigation, indicating a moderate to high decoupling between the crop and the atmosphere, so that the water vapor exchange process was controlled by the energy supply, instead of stomatal control.

The present work evaluated the Aquacrop model as a tool for climate risk analysis and yield prediction of cowpea, cultivated in a dystrophic yellow oxisol. The model was previously calibrated and validated for two harvests, in order to simulate the biomass and yield of cowpea, considering four applied water blades over its reproductive period. The good achieved results prove the model’s efficiency for this kind of simulation. After validation, the yield simulation of cowpea based on the meteorological data (2003 to 2014), soil and crop management of 12 harvests was performed. Two scenarios were given: the potential yield without water restrictions; and the actual yield, considering to pluvial availability conditions of the inserted series. The results suggested that the optimum sowing dates are between April 1st and 20th, in which there was a low yield loss (< 10 %) considering the potential yield, high probability (> 90 %) of achieving high yields (above 1300 kg ha-1) and a low risk of getting crop harvesting in the rainy period. After all, the model proved to be a feasible tool for predicting cowpea yield in the region and also over regions with similar characteristics.

PRODUTIVIDADE E EFICIÊNCIA DO USO DA ÁGUA DE CUPUAÇUZEIRO IRRIGADO NAS CONDIÇÕES CLIMÁTICAS DE CASTANHAL-PA, AMAZÔNIA BRASILEIRA     DEBORAH LUCIANY PIRES COSTA 1; IGOR CRISTIAN DE OLIVEIRA VIEIRA 2; ERIKA DE OLIVEIRA TEIXEIRA3; MATHEUS YAN FREITAS SILVA4; MARIA DE LOURDES ALCÂNTARA VELAME5 E PAULO JORGE DE OLIVEIRA PONTE DE SOUZA6   1 Laboratório de Agrometeorologia, Universidade Federal Rural da Amazônia - Campus Belém – PA, Av. Tancredo Neves, nº 2501 – Terra Firme – CEP. 66.077-830, Belém, PA, Brasil, deborahpires.agro@gmail.com. 2 Departamento de Ciências Exatas, Universidade Estadual Paulista Júlio de Mesquita Filho, Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal, Via de Acesso Prof. Paulo Donato Castellane s/n, Bairro Rural, CEP. 14.884-900, Jaboticabal/SP, Brasil, cristianigor67@gmail.com. 3 Laboratório de Agrometeorologia, Universidade Federal Rural da Amazônia - Campus Belém – PA, Av. Tancredo Neves, nº 2501 – Terra Firme – CEP. 66.077-830, Belém, PA, Brasil, eriikateixeira@hotmail.com. 4 Laboratório de Proteção de Plantas, Universidade Federal Rural da Amazônia - Campus Belém – PA, Av. Tancredo Neves, nº 2501 – Terra Firme – CEP. 66.077-830, Belém, PA, Brasil, matheus.yan.silva@gmail.com. 5Laboratório de Agrometeorologia, Universidade Federal Rural da Amazônia - Campus Belém – PA, Av. Tancredo Neves, nº 2501 – Terra Firme – CEP. 66.077-830, Belém, PA, Brasil, alcantaravelame@gmail.com. 6 Laboratório de Agrometeorologia, Universidade Federal Rural da Amazônia - Campus Belém – PA, Av. Tancredo Neves, nº 2501 – Terra Firme – CEP. 66.077-830, Belém, PA, Brasil, paulo.jorge@ufra.edu.br.     1 RESUMO   O cupuaçuzeiro é uma espécie promissora para o desenvolvimento sustentável da agricultura na Amazônia, porém, ainda está no processo de domesticação, sendo necessário estudos fitotécnicos para otimizar a produção de seus frutos. O objetivo deste trabalho foi avaliar a produtividade e eficiência do uso da água (EUA) do cupuaçuzeiro sob diferentes disponibilidades hídricas no município de Castanhal, PA. O experimento foi conduzido entre os anos de 2018 e 2020, representando duas safras, com uso de irrigação por microaspersão em um plantio de 0,3 ha da cultivar BRS-Carimbó. O delineamento experimental foi inteiramente casualizado (DIC), com quatro, tratamentos e 10 repetições, os tratamentos aplicados foram: TS (sem irrigação - sequeiro), T50, T100 e T150, referentes a 50%, 100% e 150% da evapotranspiração de referência, respectivamente. Foi realizada análise de variância, utilizou-se o teste de Tukey (p<0,05) e análise de regressão. Os resultados demonstraram melhor desempenho no T100, sendo superior em 68% na produção de frutos que o TS, a produtividade e EUA ajustaram-se a modelos de regressão polinomiais. A EUA foi máxima no T100 (2,615 kg ha-1 mm-1) e mínima no TS (1,105 kg ha-1 mm-1) Logo, indica-se que a irrigação em pomares de cupuaçuzeiro seja igual a 100% da evapotranspiração de referência.   Keywords: Theobroma grandiflorum (Wild.Ex.Spreng.) Schum, irrigação, rendimento, consórcio, clima.         COSTA, D. L. P.; VIEIRA, I. C. DE O.; TEIXEIRA, E. DE O.; SILVA, M. Y. F.; VELAME, M. DE L. A.; SOUZA, P. J. DE O. P. DE YIELD AND WATER USE EFFICIENCY OF IRRIGATED CUPUAÇU TREES UNDER THE CLIMATE CONDITIONS OF CASTANHAL-PA, BRAZILIAN AMAZON     2 ABSTRACT   Cupuaçu tree is a promising species for the sustainable development of Amazonian agriculture. However, it is still in the domestication phase and requires phytotechnical studies to optimize fruit production. The objective of this study was to evaluate the yield and water use efficiency (WUE) of cupuaçu trees under different levels of water availability in the municipality of Castanhal-PA. The experiment was performed between 2018 and 2020 during two harvests, using micro-sprinkler irrigation in a 0.3 ha plantation of the BRS-Carimbó cupuaçu cultivar. The experimental design was completely randomized, with four treatments and 10 replications. The treatments were: TS (without irrigation - rainfed), T50, T100, and T150, referring to 50%, 100%, and 150% of the reference evapotranspiration, respectively. Analysis of variance and comparison of means were performed by the Tukey test (p<0.05), in addition to regression analysis. The results showed better performance in response to T100, which had fruit production 68% higher than TS. The results of yield and WUE were adjusted by polynomial regression, with maximum WUE for T100 (2.615 kg ha-1 mm-1) and minimum for TS (1.105 kg ha-1 mm-1). Therefore, irrigation must be equal to 100% of the reference evapotranspiration in cupuaçu plantations.   Keywords: Theobroma grandiflorum (Willd. ex Spreng.) K.Schum, irrigation, yield, intercropping, climate.