Abstract:

The deficiency and disequilibrium of nutrient in coastal saline soil seriously hinder growth and development of cotton. It is urgent and necessary to study on changes of nutrient assimilation, nutrient use efficiency and dry matter accumulation of Bt cotton by measuring nutrient content and dry matter weight of different plant organs. And it can provide an important basis and guidance for economic application on fertilizers and nutrition improvement of Bt cotton in coastal saline soil. The experiments were conducted with two Bt cotton cultivars, spring cotton SCRC18 and short-season cotton SCRC19, in three types of coastal saline fields, high-, middle- and low-yield, in Yellow River Delta, Shandong province. The nutrient (N, P and K) assimilation, net photosynthetic rate (Pn) and dry matter accumulation characteristics were investigated. The results showed that main nutrient uptake of Bt cotton in middle- and low-yield fields was significantly lower than that in high-yield field. But nutrient use efficiency in physiology (NUEp) in middle- and low-yield fields was significantly higher than that in high-yield field. Average NUEp of Bt cotton in high-, middle- and low-yield fields was 4.81, 6.33, and 8.05 kg Lint kg^-1 N, 28.57, 40.06, and 50.48 kg Lint kg^-1 P, and 9.16, 11.58, and 12.76 kg Lint kg^-1 K, respectively. Generally, N was higher than K, and much higher than P in nutrient uptake ratio. Pn and biomass yield of Bt cotton in middle- and low-yield fields were obviously lower than those in high-yield field. And lint yield in middle- and low-yield fields was by 12.44% and 36.93% lower, respectively, than that in high-yield field. However, the ratio of seed cotton to straw in middle- and low-yield fields was significantly higher than that in high-yield field. Further analysis indicated, there were high salt content, and poor availability and supply capacity of nutrient in middle- and low-yield fields in coastal saline soil. These factors inhibited the nutrient assimilation and photosynthesis, and hindered growth and dry matter accumulation of Bt cotton. It was recommended that low- and middle-yield fields should have precedence over high-yield field in fertilization. It was also suggested that more P and K fertilizers should be applied in high-yield field, while more N and P fertilizers should be applied in low-yield field, according to characteristics of nutrient assimilation of Bt cotton and soil fertility in coastal saline soil.

Key words: Bt cotton, Coastal saline soil, Nutrient assimilation, Dry matter accumulation, Nutrient use efficiency in physiology