| Fruit and cotton intercropping has become main planting patterns of agricultural production in recent years in southern Xinjiang. Effect of fruit tree on shade of cotton is more serious, later maturation phenomenon of cotton was obvious, pre-frost yield was lower and yield was declined seriously under fruit and cotton intercropping. Clearing effects of nitrogen management on cotton photosynthetic matter production, yield formation and nitrogen absorption and use efficiency in shade have important theoretical and practical significance. The material was Central cotton No.49 to study effects of the relationship between cotton growth and photosynthetic characteristics and nitrogen forward, illustrating effects of nitrogen forward on cotton nitrogen absorption and use efficiency in shade and providing the theory basis on reasonable construction of nitrogen fertilization technology for fruit and cotton intercropping. The main results were as follows:Shade under the condition of the plant height, beginning section height, leaf number, pour four leaf width and pre-frost yield of cotton were all increasing trend with advance of nitrogen forward time. Leaf area index(LAI) of nitrogen forward to initial flowering stage(N1) was the largest before initial flowering stage, nitrogen forward to full flowering stage(N2) was the larger after initial flowering stage. Boll opening stage of N1 and N2 was 8 d and 5 d in advance. Fiber length decreased with advance of nitrogen forward time, fiber maturity and micronaire was opposite trend. Fiber uniformity and intensity were increased first and then decreased with advance of nitrogen forward time. Boll number per plant and boll weight of nitrogen forward to full flowering stage(N2) were highest, lint yield was 2594.13 kg·ha-1 and it had significant difference with N0 and N1. Lint yield of normal fertilization(N3) had no significant difference with N2, but pre-frost yield was low, so it affected yield.The Fv/Fo, Fv/Fm and qP of nitrogen topdressing finished at full flowering(N2)were improved after full flowering stage in the condition of shading, it(N2) was advantageous to the photosynthetic pigment which could capture light energy efficiency and speed to chemical energy, the carbon assimilation with the sufficient energy was provided, PS Ⅱ openness and ETR were increased at flower and boll stage, ΦPSⅡ and net photosynthetic rate were promoted, non-radiant energy dissipation was reduced at initial flowering stage, made the light energy capture more fully on photosynthetic production, non-radiant energy dissipation was improved at the late of flower and boll stage, more photosynthetic product was conveyed for bolls, the yield was promoted.Due to the large nitrogen fertilizer proportion of nitrogen forward to initial flowering stage(N1) in earlier stage, cotton vegetative growth was exuberant, short supply of nitrogen in later stage and low nitrogen use rate, it affected the yield formation. Vegetative organs proportion was still high at 43.72% of normal fertilization(N3) in later stage, had significant difference with other treatments and existed later phenomenon. Theoretical maximum accumulation of dry matter and nitrogen, maximum growth rate and growth eigenvalues of N2(nitrogen topdressing to full flowering end) were the largest. At the same time, nitrogen fertilizer use efficiency, nitrogen agronomy use efficiency, nitrogen partial productivity, nitrogen harvest index and maximum nitrogen momentary use efficiency were raised, it(N2) was advantageous to the accumulation and distribution of dry matter and nitrogen, the transformation from vegetative growth to reproductive growth and promotion of yield formation.To sum up, nitrogen topdressing should be appropriately forwarded to full flowering end(in the mid and last ten days of July) when the nitrogen level was consistent, it was benefit to improve photosynthetic matter production, nutrient transport and nitrogen use efficiency, thus increasing yield under fruit and cotton intercropping in southern Xinjiang. |
PDF Full Text Request