| Summary: | [Objective] This study aims to analyze the effects of the plant growth regulator Miantaijin (N,N-dimethyl piperidinium chloride and 2-N,N-diethylaminoethyl caproate) and planting density on yield and nitrogen (N), phosphorus (P), and potassium (K) uptake and accumulation in cotton. The results will clarify the high-yield cultivation techniques in the cotton direct seeding after wheat harvesting cropping system in the Yangtze River Basin. [Method] In 2017 and 2018, the cotton cultivar Guoxinzao 11-1 was planted at 3 densities (75,000, 90,000, and 105,000 plants·ha<sup>−1</sup>), and 3 Miantaijin doses (0, 1170, and 2340 mL·ha<sup>−1</sup>) were imposed. [Results] The results show that the highest yield (3551.3–3687.5 kg·ha<sup>−1</sup>) was achieved with a 90,000 and 105,000 plant·ha<sup>−1</sup> density and 1170 mL·ha<sup>−1</sup> of Miantaijin (seedling stage: 90 mL·ha<sup>−1</sup>, peak squaring stage: 180 mL·ha<sup>−1</sup>, peak flowering stage: 360 mL·ha<sup>−1</sup>, and peak bolling stage: 540 mL·ha<sup>−1</sup>). Under these conditions, the uptakes of N, P, and K were also the highest, up to 117.8 kg·ha<sup>−1</sup>, 77.4 kg·ha<sup>−1</sup>, and 116.4 kg·ha<sup>−1</sup>, respectively. N uptake was the highest from the peak flowering to peak squaring stage, while the highest uptakes of P and K were both detected from the peak squaring to peak flowering stages. We also found significant linear positive correlations between yield and the total absorptions and accumulations of N, P, and K, especially during the peak flowering–peak bolling stage. [Conclusions] The optimum dose of Miantaijin with a medium and high density could enhance the absorption of N, P, and K during the whole growth period of the cotton population, especially in the peak flowering–boll opening stage. This resulted in the highest yield of direct-seeded cotton after wheat harvesting.
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