Water depths and nitrogen rates on sugarcane growth and dry biomass accumulation

Irrigation and soil fertilization management are essential agricultural practices that improve the growth and development of sugarcane plants and, consequently, increase their production capacity, which is important for sugar and alcohol productions. In this context, the objective of this work was to evaluate the effect of water depths and nitrogen rates on the growth and dry biomass accumulation of sugarcane plants. The treatments consisted in four water depths (1,498; 1,614; 1,739; and 1,854 mm), five nitrogen rates (0; 20; 40; 80; and 120 kg ha-1) and five evaluation times. The experiment was conducted in a randomized block design with a split-split-plot arrangement and four replications, including the factors water depths, nitrogen rates, and days after planting. The dry biomasses of the plant pointer, leaves and culms, culm diameter, plant height, and number of plants were analyzed. The application of nitrogen increased the sugarcane biomass, mainly the pointer (with leaves) and dry culm biomass, and the number of plants. The highest dry culm biomass accumulation and dry leaf biomass were found at the end of the crop cycle for the treatment with the application of nitrogen rates of 80 and 120 kg ha-1. The increases in water depths applied increased the number of plants per linear meter, but the culm and dry leaf biomass did not happen.

Green onion production under strategies of replacement and frequencies of circulation of brackish nutritive solutions / Produção de cebolinha sob estratégias de reposição e frequências de circulação de soluções nutritivas salobras

The cultivation of vegetables in semi-arid regions, especially in the context of the use of brackish water, has been made possible by the use of the hydroponics technique. Thus, two experiments were carried out between December 2016 and January 2017 in a protected environment at the Federal Rural University of Pernambuco (UFRPE), Recife ­ PE, Brazil (8° 1"7" South latitude and 34° 56" 53" West longitude, and average altitude of 6.5 m), aiming at evaluating the production of green onion (cv. "Todo dia" Evergreen - Nebuka) in plants exposed to brackish nutrient solution (1.5, 3.0, 4.5, 6.0, 7.5 and 9.0 dS m-1), applied at two frequencies of circulation (twice a day - at 8 and 16 hours, and three times per day - at 8, 12 and 16 hours) in low-cost hydroponics system. In Experiment I, the nutrient solution evapotranspirated by the plants was replaced with the respective brackish water used in its preparation, and in Experiment II with UFRPE supply water (0.12 dS m-1). In both cases, a completely randomized experimental design was used, in a 6 x 2 factorial scheme, with five replications. It was concluded that under replacement with brackish water, the increase in the frequency of circulation attenuated the losses imposed by the salinity to the biometric variables and of the production of fresh and dry phytomass of the plants; the water supply replenishment had a greater mitigating role in relation to the damage caused by the salinity with the increase of the electrical conductivity of the nutrient solution.

O cultivo de hortaliças em regiões semiáridas, especialmente no contexto de uso de águas salobras, tem sido viabilizado pelo uso da técnica da hidroponia. Diante disto, entre janeiro de 2016 e abril de 2017, foram conduzidos dois experimentos em ambiente protegido na Universidade Federal Rural de Pernambuco (UFRPE), Recife, PE (8° 1"7" Sul e 34° 56" 53" Oeste, altitude média de 6,5 m), objetivando-se avaliar a produção da cebolinha (cv. Todo ano Evergreen - Nebuka) em plantas expostas a soluções nutritivas salobras (1,5; 3,0; 4,5; 6,0; 7,5 e 9,0 dS m-1) aplicadas em duas frequências de circulação (duas vezes ao dia - às 8 e às 16 horas; e três vezes ao dia - às 8, 12 e 16 horas). Em ambos os casos, utilizou-se um delineamento experimental inteiramente casualizado, em esquema fatorial 6 x 2, com cinco repetições. No Experimento I, a lâmina de solução nutritiva evapotranspirada pelas plantas foi reposta com a respectiva água salobra utilizada no seu preparo e, no Experimento II, com água de abastecimento da UFRPE (0,12 dS m-1). Concluiu-se que sob reposição com água salobra, o aumento da frequência de circulação atenuou as perdas impostas pela salinidade às variáveis biométricas e de produção de fitomassa fresca e seca das plantas; a reposição com água deabastecimento passou a ter maior papel mitigador em relação ao dano causado pela salinidade com o aumento da condutividade elétrica da solução nutritiva.