The effects of different amounts of nitrogen and phosphorus in early cotton (Gossypium hirsutum L.) cultivar

This research was carried out at Agricultural and Natural Resources Research Center, Isfahan, Islamic Republic of Iran (Kabootar abad) for two years (2006-2007). The experiment was conducted as a split plot arranged in randomized block design with four replications. Treatments were four levels of N fertilizer [110, (160 = Soil and Water Research Institute recommendation), 210 and 260 kg ha-1] as main plots, and four rates of P fertilizer [23, (46= Soil and Water Research Institute recommendation), 70 and 92 kg ha-1) as subplots. Results showed that consuming 110 kg N fertilizer, production would be similar to other levels of​​ N treatments. So this treatment is both economically and environmentally, is recommended. But, the nitrogen concentration in leaves was significantly reduced in this treatment. Unlike the results of nitrogen fertilizer, reduced of phosphate fertilizer consumption (compared to the recommended amount of Soil and Water Research Institute) caused a significant reduction in yield. This lower performance was associated with a reduced number of capitula per plant and weight of capitula. In this treatment, the phosphorus concentration in leaves remained constant but the amount of phosphorus in the 0-30 cm soil depth was reduced significantly. In this study the interaction of nitrogen and phosphorus on yield was not statistically significant.