The Effects of the Nitrogen Fertilizer Rates on the Uptake and Yield of Cotton on Calcareous Soil
Sep 12, 2018
Excessive nitrogen fertilizer rates in Upland cotton (Gossypium hirsutum L.) produces high levels of nitrates in calcareous soils. The experiments were conducted in the Experimental Station of Vardates in central Greece, during the seasons 1992 and 1993. The objectives were to examine the effects of variable nitrogen rates on the nitrogen uptake and the yield of cotton in calcareous soils. The experiments were conducted in complete, randomized blocks, using the nitrogen rates of 0, 60, 90, 120, 150, and 180 kg.ha-1, while phosphorus and potassium were kept constant at 80 kg.ha-1. The dry matter content (grams per plant) and nitrogen uptake, as well as the concentration of NO3- (ppm) in soil depth of 0-30 cm, differed for the applied nitrogen rates and stages of plant growth. Cotton plants appeared to have a higher dry matter content and nitrogen uptake at the ‘blooming’ stage while the lowest value of concentration of NO3- (ppm) in soil appeared at the ‘squares’ stage. The yield of seed cotton of 4400 - 4500 kg.ha-1 was not significantly affected by the high nitrogen rates of 120 - 180 kg.ha-1, (r2 = 0.4). The yield of seed cotton (4733 kg. ha-1) and the dry matter content ( 100 g.plant-1), were positively affected by the rates of 60 kg N. ha-1, 80 kg P2O5. ha-1 and 80 kg K2O. ha-1 (r2 = 0.75 ).