Main content area

Photosynthetic characteristics of boll subtending leaves are substantially influenced by applied K to N ratio under the new planting model for cotton in the Yangtze River Valley

Hafeez, Abdul, Ali, Saif, Ma, Xiaolei, Tung, Shahbaz Atta, Shah, Adnan Noor, Ahmad, Shoaib, Chattha, Muhammad Sohaib, Souliyanonh, Biangkham, Zhang, Zhao, Yang, Guozheng
Field crops research 2019 v.237 pp. 43-52
adenosine triphosphate, biomass, chlorophyll, cotton, crop yield, fertilizer rates, field experimentation, leaf area, leaves, models, photosynthesis, planting, ribulose-bisphosphate carboxylase, river valleys, sowing, water content, Yangtze River
A new cotton planting model has been developed for the Yangtze River Valley which involves late sowing, high plant density and less applied N compared with the traditional transplanted cotton production. However, it is unknown if the K application rate can be reduced to achieve a 1:1 or lower applied K2O: N ratio. Therefore, we conducted field experiments to investigate the optimal K2O: N ratio for cotton under the new planting model. The study involved the evaluation of the photosynthetic attributes of the boll subtending leaves in relation to crop yield. A two-year (2016-17) field experiment was conducted with three K to N ratios [K08 (0.8:1), K10 (1.0:1) and K12 (1.2:1)] with 210 kg N ha−1 applied to all treatments. Our results indicated that the increased K application improved the photosynthetic attributes of the boll subtending leaves, leading to increased crop yield. Compared with K08, K10 and K12, respectively, enhanced the photosynthetic rate by 7–32% and 36–59%, chlorophyll fluorescence by 4–13% and 8–35%, chlorophyll content by 5–61% and 20–75%, total Rubisco activity by 7–23% and 30–55%, leaf area by 21–72% and 32–87%, leaf biomass by 12–36% and 31–51%, and relative water content of the boll subtending leaves by 2–8% and 13–16%. Also, compared with K08, leaf ATP content and SLW (specific leaf weight) were down-regulated in K10 and K12 by 7–23% and 1–26%, respectively. Moreover, statistically similar contribution to yield was found between K10 and K12, suggesting that under the late sowing, high density and low applied N model, a 1:1 K2O: N application rate N (K10) is the optimal choice for maximum financial return without reducing cotton yield.