ABSTRACT Producers in the northeastern semiarid region of Brazil have been cultivating irrigated corn. The commercialized product comprises mainly green ears and silage. However, the irrigation of crops for dry grain has been questioned regarding costs and price competitiveness in relation to the same non-irrigated product cultivated in other regions. In recent years, the use of drip tapes and fertigation has spread among corn producers in the region. The aim of this study was to determine the N dose, via fertigation, which provides the maximum economic production of corn for dry grain, in two crop seasons (summer and winter), in the semiarid region of Brazil. The experimental design was performed in randomized blocks, with four replications. In both crops, the treatments consisted of four doses of N (0, 80, 160, and 240 kg ha-1) applied in the form of urea. In the hybrid corn (Bt Feroz), the N content was evaluated in terms of leaves, grain yield, gross and net incomes, the rate of return, and the profitability index. Independent of the crop season, the yield of dry grain (5,441.03 kg ha-1) was highest when the corn was fertigated with a dose of 104.05 kg ha-1 N. The highest net incomes of the dry grain were obtained with 80 kg ha-1 N in summer (R$ 1,190.78 ha-1) and 160 kg ha-1 N in winter (R$ 2,757.54 ha-1). The winter crop was more favorable to the economic production of dry grain.

ABSTRACT. The objective of this work was to determine the adequate nitrogen (N) dose via fertigation associated with the maximum economic production of maize for silage, in two agricultural crops (summer and winter), in the municipality of Canindé de São Francisco-SE, Brazil. The experimental design was in randomized blocks, with four replicates. The treatments consisted of four doses of N (0, 80, 160, and 240 kg ha-1) using urea. The cultivar planted was the hybrid Bt Feroz. The evaluated characteristics were as follows: shoot fresh and dry mass productivity, gross and net incomes, the rate of return and net profit margin. There was an interaction between N doses and agricultural crops for all variables. Higher agroeconomic efficiency in the production of maize for silage was obtained from the winter harvest. In the summer crop, the rate of return (1.82) and the net profit margin (45.52%) were highest when the plants were fertigated with 56.04 and 58.92 kg ha-1 of N, respectively. In winter, the yields of fresh mass, gross and net incomes increased linearly with increasing doses of N, with a profit proportional to the invested capital since nitrogen fertigation did not influence the rate of return (2.24) and the net profit margin (55.22%).

Resumo: O objetivo deste trabalho foi determinar a dose de nitrogênio para fertirrigação associada à máxima produtividade de milho verde (Zea mays) com menor custo de produção, em duas safras agrícolas no semiárido brasileiro. O delineamento experimental foi em blocos ao acaso, com quatro repetições, e os tratamentos consistiram em doses de N (0, 80, 160 e 240 kg ha-1), na forma de ureia, via irrigação por gotejamento. A cultivar utilizada foi o híbrido Bt Feroz. As características avaliadas foram: número e massa de espigas comercializáveis, renda bruta, renda líquida e taxa de retorno. As maiores quantidades de espigas comercializáveis foram alcançadas com 152,52 kg ha-1 de N no verão (41.183,84 espigas por hectare) e 190,31 kg ha-1 de N no inverno (53.291,25 espigas por hectare). Nas duas safras, houve variação nos custos de produção entre R$ 2.422,12 ha-1 e R$ 3.320,95 ha-1 sem N e com 240 kg ha-1 de N, respectivamente. A safra de inverno apresentou maior produtividade e rentabilidade de espigas verdes com fertirrigação com 160 kg ha-1 de N. No semiárido brasileiro, a máxima produtividade de milho verde com menor custo de produção é alcançada com a fertirrigação com 90 kg ha-1 de N, em ambas as colheitas.

Abstract: The objective of this work was to determine the nitrogen rate for fertigation associated with the maximum productivity of green corn (Zea mays) with a lower production cost, in two harvest seasons in the Brazilian semiarid region. The experimental design was a randomized complete block with four replicates, and the treatments consisted of four N rates (0, 80, 160, and 240 kg ha-1) in form of urea, applied via drip irrigation. The used cultivar was the Bt Feroz hybrid. The evaluated characteristics were: number and mass of marketable ears, gross income, net income, and rate of return. The greatest amounts of marketable ears were reached with 152.52 kg ha-1 N in summer (41,183.84 ears per hectare) and 190.31 kg ha-1 N in winter (53,291.25 ears per hectare). In the two harvests, there was a variation in production costs between R$ 2,422.12 ha-1 and R$ 3,320.95 ha-1 without N and with 240 kg ha-1 N, respectively. The winter harvest showed higher productivity and profitability of green ears with fertigation with 160 kg ha-1 N. In the Brazilian semiarid, the maximum productivity of green corn with the lowest production cost is reached with fertigation with 90 kg ha-1 N, in both harvests.

RESUMO A produção de hortaliças é caracterizada pelo uso intensivo da terra, pela alta demanda de insumos e pela necessidade de gestão estratégica com uma abordagem agroecológica para sustentar a produção. Indicadores agronômicos foram avaliados em alface adubada com diferentes quantidades de biomassa de Flor - de-seda, em diferentes épocas de incorporação ao solo e plantadas em duas estações de cultivo (primavera e outono-inverno) em Serra Talhada, Pernambuco, Brazil. O delineamento experimental consistiu em blocos ao acaso com três repetições e os tratamentos arranjados em esquema fatorial 4 x 4. O primeiro fator foi à quantidade de biomassa de Flor-de-seda (5,4; 8,8; 12,2 e 15,6 t ha-1 em base seca) e o segundo os tempos de incorporação do adubo (0, 10, 20 e 30 dias antes do transplante da alface). As características avaliadas na cultura da alface foram: diâmetro de plantas, número de folhas por planta, altura de plantas, produtividade de massa verde e massa seca da parte aérea. As produtividades máximas de massa verde e seca foram obtidas na quantidade de biomassa de Flor-de-seda de 15,6 t ha-1 incorporada no solo. Observou-se uma sincronia entre a oferta de nutrientes pelo adubo verde e o período de máxima demanda pela alface nos tempos de incorporação de 10 (primavera) e 20 dias (outono-inverno) antes do transplantio. O cultivo na primavera resultou em maior crescimento vegetativo para a cultura.

ABSTRACT The production of vegetable crops is characterized by intensive land use, high input demands and the requirement of strategic management adoption with an agro-ecological approach. In this study, agronomic indicators were evaluated in lettuce fertilized with different amounts of roostertree biomass; fertilizer was incorporated into the soil at distinct times and seedlings were planted in two cropping seasons (spring and autumn-winter) in Serra Talhada, Pernambuco state, Brazil. The experimental design consisted of randomized complete blocks with three replications and treatments arranged in a 4 x 4 factorial scheme. The first factor was the amounts of roostertree biomass (5.4, 8.8, 12.2, and 15.6 t ha -1 on a dry basis) and the second the manure incorporation times (0, 10, 20, and 30 days before lettuce transplanting). The variables evaluated in the lettuce crop were: plant height and diameter, number of leaves per plant, productivity of green mass, and dry shoot mass. Maximum productivity and dry shoot mass were obtained using fertilization with 15.6 t ha -1. A synchrony between supply of nutrients by green manure and the period of maximum demand by lettuce was observed in the incorporation times of 10 (spring) and 20 (autumn-winter) days before transplanting. Cultivation in the spring resulted in higher vegetative growth.