Amaranth (Amaranthus hypochondriacus L.), which is considered an alternative source of vegetable protein, is grown particularly under rainfed conditions. Therefore, it is important to look for better management practices that lead to a more efficient use of resources, such as water and essential nutriments, to obtain higher yields. The aim of this work was to determine the influence of nitrogen and plant density on phenology, nitrogen and water use efficiency (WUE), biomass production, and seed yield of amaranth planted on June 11, 1999, with 0, 10, and 20 g m(-2) N and 12.5, 25.0, and 33.3 plants m(-2). With the application of N and with a higher plant density (PD), the efficiency in water use and in N was greater, and in consequence, biomass production and yield increased as well. These increments were higher with higher N level and higher DP. In this way, with 20 g N m(-2) and 33.3 plant m(-2) a biomass production of 2827 g m(-2) and seed yield of 346 g m(-2) were obtained. Phenology was not affected by the treatments. The requirement of sowing heat units to physiological maturity was 1629 UC and 385 mm of water used in evapotranspiration.

Water and nitrogen (N) availability are the main factors affecting biomass and grain production in maize cultivation. The lower N absorption of corn grown under rainfed conditions is due to lower demand resulting from lower growth of aboveground biomass and root system. Under irrigation conditions, high N rates can inhibit absorption due to mineralization, especially in areas with high organic matter content. Therefore, the main objective of this study was to evaluate the combined effect of nitrogen fertilization, water availability, and plant density on grain and water productivity in maize. Three experiments were carried out in the 2022/23 growing season: Santa Maria (SM), Cruz Alta (CA), and Boa Vista do Cadeado (BVC). In CA and BVC, the experimental design consisted of a randomized block in a bifactorial 2x4 scheme with four replications. Factor A consisted of two plant densities (7.0 and 8.5 plants m-2), while factor D consisted of four topdressing nitrogen rates (0, 75, 15,0 and 300 kg ha-1). In CA, the experiment was conducted under a central pivot irrigation system, while in BVC, the experiment was carried out in a rainfed environment. In SM, a three-factor DBC (2x2x4) was used, where factor A consists of irrigation management (irrigated and rainfed), factor C consists of plant densities, and factor D consists of N rates (as in CA and BVC experiments). The SIMDualKc model was used to simulate the soil water balance and consumption in different environments. The model was calibrated with the irrigation treatment of the SM experiment, 7.0 plants m-2, and 300 N rate. Soil water content was monitored using FDR sensors to a depth of 80 cm. The results showed a significant difference in grain yield for plant density factor in CA, with yields of 15.6 and 16.6 Mg ha-1 for populations of 7 and 8.5 pl m-2, respectively. In the rainfed condition, decreasing linear behavior was observed with increasing dose. Lower water availability reduced N absorption and demand, which was reflected in lower LAI and plant height. In SM, rainfed yield was 4.35 Mg ha-1compared to 3.6 Mg ha-1 in BVC. The lower yield for BVC is due to the water deficit that occurs during peak demand. Greater available soil water (ASW) and occasional rainfall during the grain-filling period favored the higher yield of rainfed corn in SM. The lack of responsiveness of corn yield to varying N rates in an irrigated environment may be related to mineralization and higher N losses through leaching. The SIMDualKc model adequately reproduced the observed ASW (available soil water) under the different growing conditions, with bo values ranging from 0.96 to 1.03, R2 between 0.89 and 1.0, and RMSE ranging from 3.2 to 12.10 mm, which represents less than 15% of the average observed ASW. | A disponibilidade de água e nitrogênio (N) são os principais fatores que influenciam a produção de biomassa e grãos na cultura do milho. A menor absorção de N pelo milho cultivado em sequeiro deve-se a menor demanda, devido ao menor crescimento da parte aérea e sistema radicular. Em condições irrigadas, altas doses de N podem inibir sua absorção devido à mineralização, especialmente em áreas com alto teor de matéria orgânica. Assim, o principal objetivo do trabalho foi avaliar a efeito combinado de níveis de adubação nitrogenada, disponibilidade de água e densidade de plantas no desenvolvimento e produtividade de grãos e água no milho. Três experimentos foram conduzidos na safra 2022/23: Santa Maria (SM), Cruz Alta (CA) e Boa Vista do Cadeado (BVC). Em CA e BVC, o delineamento experimental foi em blocos ao acaso, em esquema bifatorial 2x4, com quatro repetições. O fator A foi constituído de duas densidades de plantas (7,0 e 8,5 plantas m-2), enquanto o fator D foi constituído de quatro doses de nitrogênio em cobertura (0, 75, 150 e 300 Kg ha-1). Em CA, o experimento foi conduzido sob pivô central, enquanto que, em BVC, utilizou-se área de sequeiro. Em SM, usou-se um DBC tri-fatorial (2x2x4), com o fator A sendo composto pelo manejo de irrigação (irrigado e sequeiro), o fator C foi constituído pelas densidades de plantas, enquanto o fator D foi composto pelas doses de N (iguais às dos experimentos em CA e BVC). O modelo SIMDualKc foi utilizado para simular o balanço hídrico do solo e o uso da água nos diferentes ambientes. O modelo foi calibrado com o tratamento irrigado, 7,0 plantas m-2 e dose de 300 N, do experimento de SM. O conteúdo de água no solo foi monitorado utilizando sensores FDR, até a profundidade de 80 cm. Os resultados demonstraram que houve diferença significativa no rendimento de grãos para o fator densidade de plantas, em CA, com rendimentos de 15,6 e 16,6 Kg ha-1, para as populações de 7 e 8.5 pl m-2, respectivamente. Na condição de sequeiro, observou-se comportamento linear decrescente com o aumento da dose. A menor disponibilidade de água diminuiu a absorção e requerimento de N, representado por um menor IAF e altura de plantas. Em SM, o rendimento de sequeiro foi de 4,35 Kg ha-1, contra 3,6 Kg ha-1em BVC. O menor rendimento em BVC deve-se ao fato de o déficit hídrico ter ocorrido no período de máxima demanda. A maior disponibilidade de água no solo e precipitações eventuais no período de enchimento de grãos favoreceu o maior rendimento do milho de sequeiro em SM. A não resposta do rendimento do milho a diferentes doses de N em ambiente irrigado pode estar relacionada a mineralização e maiores perdas de N por lixiviação. O modelo SIMDualKc reproduziu adequadamente a ASW (água disponível no solo) observada nas diferentes condições de cultivo, com valores de bo variando entre 0,96 e 1,03, R2 entre 0,89 e 1,0 e RMSE variando entre 3.2 a 12.10 mm, o que representa menos de 15% da média de ASW observada.

The effect of radial distance from water sources (RDW) on plant volume, hiding cover (HC) and the presence of white-tailed deer was assessed. The study was conducted in the state of Puebla, Mexico. Stratified random sampling was used to select five areas with a RDW of less than 800 m, four between 800-1,600 m and four greater than 1,600 m. Plant volume was estimated in these areas and they were the starting point of transects in which HC and the number of white-tailed deer and coyote fecal pellet groups (PGs) were estimated. The number of white-tailed deer PGs increased as the RDW increased (Tukey; P < 0.05), while coyote PGs remained within the 800-m radius (X² = 0.004). The RDW did not affect HC (Tukey, P > 0.05). The relationship between RDW, HC and PGs was established using Poisson and polynomial regression. Poisson regression showed that RDW and HC significantly changed (X²; P < 0.0004 and P < 0.0001) the PG number. The polynomial equation showed that HC has a good correlation (R² = 0.72) with PGs. | El efecto de la distancia radial al agua (DRA) sobre el volumen vegetal, la cobertura de escape (CE) y la presencia del venado cola blanca, se evaluó. El trabajo se realizó en el estado de Puebla, México. Cinco áreas con una DRA menor a 800 m, cuatro entre 800-1,600 y cuatro mayores a 1,600 m, fueron seleccionadas utilizando un modelo completamente al azar. El volumen vegetal se estimó en estas áreas y fueron el punto de inicio de transectos en los cuales se estimó la CE y el número de grupos fecales (GFs) de venado cola blanca y coyote. Los GFs de venado cola blanca aumentaron conforme aumentaba la DRA (Tukey; P < 0.05) mientras que los de coyote se mantuvieron dentro de los 800 m de radio (X² = 0.004). La DRA no afectó la CE (Tukey; P > 0.05). La relación entre la DRA, CE y GFs, se estableció con un análisis de regresión de Poisson y un polinomial. La regresión de Poisson mostró que la DRA y la CE modifican significativamente (X²; P < 0.0004 y P < 0.0001) el número de GFs. La ecuación polinomial mostró que la CE tiene buena correlación (R² = 0.72) con los GFs.