O sucesso na produção de alface (Lactuca sativa L.) começa pela obtenção de mudas com boa qualidade sendo necessário a utilização de substratos que fornecem condições químicas e físicas favoráveis ao desenvolvimento da planta. O reaproveitamento de resíduos na produção de substratos pode ser uma proposta interessante para a produção de mudas. O trabalho objetivou avaliar a influência de biochar produzido a partir da serragem de eucalipto, no desenvolvimento de mudas de alface. O experimento foi conduzido em casa de vegetação com delineamento experimental inteiramente casualizado, com sete tratamentos e três repetições. Utilizou-se a cultivar Grandes Lagos e sete substratos sendo um comercial, Bioplant® (BPL) e seis formados a partir do substrato comercial, Bioplant® + biochar (BC 5, BC 10, BC 15, BC 25, BC 50 e BC 75% m/m). Foram avaliadas as variáveis percentagem de emergência (E), índice de velocidade de emergência (IVE), comprimento da parte aérea (CPA) e sistema radicular (CSR), massa fresca da parte aérea (MFPA) e do sistema radicular (MFSR) e massa seca da parte aérea (MSPA) e do sistema radicular (MSSR), 25 dias após a semeadura. A adição de biochar, ao substrato comercial, Bioplant®, na concentração de 5% em massa, apresentou viabilidade para ser utilizado como condicionador de substrato no desenvolvimento de mudas de alface da cultivar Grandes Lagos.

In the rigion Nordeste, the peanutis cultivated almost exclusively by family agriculture producers with low technological levels, in addition to the low use of inputs, essential to ensure better productivity. Objective to evaluate the performance and productivity of peanut subjected to doses of fertilization and spacing between plants, in the rainfed system and irrigation system. The experiment was conducted at the Federal University of cariri. Two experiments were conducted in randomized blocks in parcel scheme subdivided, with four replicates.The plots were four doses of fertilization on sowing (0, 50, 100 and 150%) and the subplots two spaces between plants (10 and 20 cm). The peanut cultivar used was the BRS151L7. Sowing was carried out manually, depositing-if 5 and 10 as the spacing between plants. The harvest was carried out manually to 90 days after sowing.The variables population initial and final population showed significant (p < 0.01) to the spacing between plants in system rainfed and irrigation system. The mass of plants and grains per plant showed significant difference to 1% in the spacing for the irrigation system. In the fertilizing factor, the height of plants was the only variable thatshowed significance (p < 0.05). The application of 80% of the recommended dose of phosphorus and potassium is enough to meet the need of culture. The 10 cm spacing between plants was the best for culture.The use of supplemental irrigation has increased by more than 300% the productivity of grain and peanut pods.

No abstract

A utilização de biocarvão na produção de substratos pode ser uma estratégia agronômica interessante para produção de mudas. Com o objetivo de avaliar a influência do biocarvão produzido a partir do resíduo do fruto do cafeeiro, no desenvolvimento de mudas de alface quando adicionado a substrato comercial, foi conduzido experimento em casa de vegetação, com delineamento experimental inteiramente casualizado, com cinco tratamentos e oito repetições. Utilizou-se a cultivar Grandes Lagos (Lactuca sativa L.) e cinco substratos, sendo um comercial, Bioplant® (PLT) e quatro formados a partir do substrato comercial, Bioplant® + biocarvão (BC 5, BC 10, BC 15 e BC 25). Foram avaliadas as variáveis percentagem de emergência (E), índice de velocidade de emergência (IVE), comprimento parte aérea (CPA) e sistema radicular (CSR), massa fresca da parte aérea (MFPA) e do sistema radicular (MFSR) e massa seca da parte aérea (MSPA) e do sistema radicular (MSSR), 25 dias após a semeadura. Os tratamentos, BC 5, BC 10, BC 15, apresentaram 100% de plântulas emergidas e IVE de 37,1 Plântulas dia-1; 37,5 Plântulas dia-1 e 37,7 Plântulas dia-1, respectivamente, resultados comparáveis ao tratamento PLT. O tratamento BC 10, apresentou maiores valores para as variáveis CPA, CSR, MFPA, MFSR, MSPA e MSSR (2,38 cm; 5,16 cm; 89,1 mg; 88,8 mg; 12,7 mg; 10,3 mg, respectivamente), diferenciando-se significativamente do tratamento PLT. A adição de biocarvão (10 % em massa), foi uma alternativa viável para ser utilizado como condicionador do substrato comercial, Bioplant®, para produção de mudas de alface da cultivar Grandes Lagos.

This study aimed to evaluate the performance of six machine-learning models in forecasting corn (Zea mays L.) grain yield before harvest using, as input, variables in the models, some of the most-used vegetation indices (VIs) and spectral bands in the literature, as well as using data at 770 and 980 sum of degree days (SDD).The field study was carried out in a commercial area in the 2017-2018 and 2018-2019 harvests. Spectral data were obtained from Sentinel-2 satellite images and were used as input variables in the proposed models: artificial neural networks (ANN), k-nearest neighbors (KNN), random forest (RF), and support vector machine (SVM). The maximum R 2 and minimum values of mean absolute error (MAE) and RMSE were 0.89, 0.33, and 0.42 t ha −1 , respectively, for the RF algorithm using all input variables. The results obtained in the present study show that it is possible to predict corn grain yield 80 d before harvest using only VIs for the crop. Testing the various combinations of spectral bands and VIs resulted in obtaining the GREEN band and the VI global environment monitoring index (GEMI) as the best predictor variables in the present study. The use of more than one SDD did not improve the performance of the models tested. The models developed using data at 980 SDD obtained the best precision and accuracy performance both in the scenario with all model input variables and with the two best predictors. The KNN algorithm obtained the best performance in the precision and accuracy metrics for most of the scenarios studied in the present work.

Objetivou-se com o presente trabalho avaliar o efeito de diferentes plantas de cobertura sobre as características agronômicas e produtividade da cultura da soja sob sistemas de cultivo Plantio Direto e Convencional. O experimento foi realizado em área experimental no município de Monte Carmelo-MG, nos anos agrícolas 2016/2017 e 2018/2019, utilizando delineamento experimental em blocos ao acaso, com quatro repetições, em esquema de faixas. Os tratamentos foram constituídos por seis espécies de plantas para cobertura de solo (2016/2017 foi semeado crotalária, feijão guandu, lab lab, milheto, sorgo e pousio e 2018/2019 foram crotalária, nabo forrageiro, feijão guandu, milheto, lab lab e pousio) e por dois sistemas de cultivo (plantio direto e plantio convencional).  A cultivar de soja utilizada em 2016/2017 foi a SYN 1562 IPRO*(RR) e em 2018/2019 a NS 7667 (Ipro, Nidera). Nas cultivares de soja foram avaliadas as seguintes características agronômicas: altura inicial das plantas, altura da primeira vagem, altura final, número de vagens por planta, número de sementes por vagem e produtividade de grãos de soja. As maiores alturas de plantas de soja foram após o cultivo de crotalária, feijão guandu, lab lab e pousio. A altura da primeira vagem foi maior sobre a palhada de crotalária, lab lab e pousio e milheto. O uso do milheto, nabo forrageiro e feijão guandu proporcionaram maior número de vagens por planta em soja cultivada. Em 2016/2017 o sistema de plantio direto proporcionou maior produtividade da soja. No sistema de plantio convencional todas as plantas de cobertura proporcionaram aumento na produtividade em 2018/2019.

The appropriate time for leaf collection to evaluate the nutritional status of the coffee tree should be carried out when the nutrient is in higher levels in the leaves, which may vary according to the phenological stage of the fruits. Macro and micronutrients do not show the same pattern regarding the period of highest leaf content. Therefore, it is coherent to define different times of leaf collection for each nutrient. The objective of this study was to verify the most suitable times for collecting leaves to evaluate the nutritional status of coffee plants based on the phenological development of coffee fruits. The experiment was carried out in a commercial field, in which six coffee cultivars were used (Acauã Novo, Bourbon Amarelo, Catuaí Vermelho IAC 144, Catucaí 20/15, IAC 125 RN and IPR 100). The collections were carried out in four phenological phases of coffee fruit development (floral bud maturation, chumbinho, fruit expansion, and fruit granulation). The periods with the highest concentrations varied based on the phenological stages of the fruits, and differences in concentrations were also observed between the cultivars examined. The highest zinc concentration in the leaves was observed in the maturation phase of the floral bud. Foliar collection for the diagnosis of the nutritional state of the coffee plant should be done for each nutrient based on the phenology of the fruits.

&lt;p&gt;&lt;strong&gt;Pedotransfer functions to mapping total and adsorbed phosphate using Vis-NIR (DRS) &lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Jos&amp;#233; Marques J&amp;#250;nior&lt;sup&gt; a&lt;/sup&gt;, Rom&amp;#225;rio Pimenta Gomes&lt;sup&gt; a&lt;/sup&gt;, Luis Fernando Vieira da Silva&lt;sup&gt; a&lt;/sup&gt;, Jo&amp;#227;o de Deus Ferreira e Silva&lt;sup&gt; a&lt;/sup&gt; &amp; La&amp;#233;rcio Santos Silva&lt;sup&gt; a&lt;/sup&gt;&lt;/p&gt;&lt;p&gt;Department of Soils and Fertilizers, Research Group CSME - Soil Characterization for Specific Management, State University of S&amp;#227;o Paulo (UNESP), Via de Acesso Prof. Paulo Donato Castellane s/n, 14883-292 Jaboticabal, S&amp;#227;o Paulo, Brazil&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Soil oxides-Fe can be an excellent predictor of spatial variability of total and adsorbed P, contributing to rapid mapping, low cost and differentiation of minimum areas of phosphate fertilizer management. In the Western Paulista Plateau (Brazil) were collected 300 soil samples representing the lithological (sandstone and basalt) and geomorphic variability (less, moderately and highly dissected), at a depth of 0.0 &amp;#8211; 0.2 m. The total (P&lt;sub&gt;total&lt;/sub&gt;) and adsorbed phosphorus (P&lt;sub&gt;ads&lt;/sub&gt;) determined by conventional methods and hematite and goethite by X-ray diffraction (XRD). By partial least squares regression (PLS) and chemometric calibration, internal validation and external calibration, the Ptotal and Pads were estimated by diffuse reflectance spectroscopy (Vis-NIR-DRS), using hematite (Hm) and goethite (Gt) as a predictor. Then, the spatial pattern was obtained by geostatitic analysis. Phosphorus ware influenced by geology and dissection of the landscape and is a covariate of Hm and Gt, important indicators of environments with high or low P adsorption and content potential. Partial least squares (PLS) regression analysis of the spectral data demonstrated the influence of iron oxides on P&lt;sub&gt;total&lt;/sub&gt; and P&lt;sub&gt;ads&lt;/sub&gt;, whereby Hm affects the former and Gt the latter. The lower maximum phosphorus adsorption capacity indicates the scarcity of P minerals and Fe oxides from sandstone sediments, with severe risk of phosphate loss and environmental damage. Significant correlation between P&lt;sub&gt;total&lt;/sub&gt; and Hm and P&lt;sub&gt;ads &lt;/sub&gt;and Gt in Vis-NIR-DRS indicates the potential of this study in mapping large areas based on iron oxides, which can be used to develop soil P inventories as well as monitor and estimate the future impacts of land use, considering the complex relations between soil and landscape.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords:&lt;/strong&gt; Diffuse reflectance spectroscopy, goethite, hematite, geostatistics.&lt;/p&gt;