Effects of reduced nitrogen application rate on drip‐irrigated cotton dry matter accumulation and yield under different phosphorus and potassium managements

Abstract

To elucidate effects of reduced N application rate on dry matter accumulation and yield of drip-irrigated cotton (Gossypium hirsutum L.) under different phosphorus and potassium managements (PK-Ms), field studies with four reduced N application rates and four PK-Ms were conducted in 2018 and 2019. Results show that after early peak boll-forming (PB) stage, the leaf area (LA) in N3PK-M3 was the highest among all treatments. The net assimilation rate (NAR), crop growth rate (CGR), boll dry weight (BDW), and boll growth rate (BGR) were highest in N2, followed by N3 with insignificant differences, and those parameters in PK-M3 were the highest.The reproductive/vegetative biomass ratio (RVR) for N3PK-M3 was the highest. The CGR, BDW, BGR, and NAR for N3PK-M3 were insignificantly lower than those for N2PK-M3, which increased yield in N2PK-M3 and N3PK-M3 treatments. Correlation analysis showed that BGR was positively related with CGR and NAR from peak flowering (PF) stage to boll opening (BO) stage, and CGR was significantly correlated with NAR and LA from PF to BO stage, and BO stage, respectively. Moreover, the yield was positively correlated with boll weight (BW) and boll number (BN), and BGR was significantly correlated with BN and BW from peak squaring stage to late PB stage. Therefore, high yield in N3PK-M3 due to higher value in LA after bollforming stage, with higher NAR, CGR, RVR, and BGR, suggesting that early boll formation and successive partitioning of dry matter in boll growth were important factors for yield formation.

Variation of Nitrogen, Phosphorus, and Potassium Contents in Drip-Irrigated Cotton at Different Yield Levels under Combined Effects of Nitrogen, Phosphorus and Potassium

“…Three cotton plants were selected from each plot at the full square stage (FS), the full flowering stage (FF), the early-full bolling stage (EFB), the late-full bolling stage (LFB), and the boll-opening stage (BO), and divided into leaves, stems and reproductive organs. Afterward, the different parts were placed at 105 • C for 30 min and then dried at 80 • C until their weights were constant [5,10]. The Nc, Pc, and Kc in cotton leaves, stems, and reproductive organs were estimated, as well as the N accumulation (Na), P accumulation (Pa), and K accumulation (Ka) in cotton plants.…”

“…Rational fertilization management can reduce production costs without reducing yields [5,10], but the variation in N, P, and K content of cotton at different yield levels during critical growth stages remains to be studied. Research has demonstrated that N, P, and K contents and accumulation could provide a reliable evaluation of the crop growth conditions and yield predictions [11,12].…”