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Effects of plant density and nitrogen rate on cotton yield and nitrogen use in cotton stubble retaining fields
WANG Shi-hong, MAO Li-li, SHI Jia-liang, NIE Jun-jun, SONG Xian-liang, SUN Xue-zhen
2021, 20 (8): 2090-2099.   DOI: 10.1016/S2095-3119(20)63323-8
Abstract149)      PDF in ScienceDirect      
Increasing nitrogen (N) rate could accelerate the decomposition of crop residues, and then improve crop yield by increasing N availability of soil and N uptake of crops.  However, it is not clear whether N rate and plant density should be modified after a long period of cotton stubble return with high N rate.  This study seeks to assess the effects of N rate and plant density on cotton yield, N use efficiency, leaf senescence, soil inorganic N, and apparent N balance in cotton stubble return fields in Liaocheng, China, in 2016 and 2017.  Three plant densities 5.25 (D5.25), 6.75 (D6.75) and 8.25 (D8.25) plants m–2 and five N rates 0 (N0), 105 (N105), 210 (N210), 315 (N315), and 420 (N420) kg ha–1  were investigated.  Compared to the combination used by local farmers (D5.25N315), a 33.3% N reduction and a 28.6% increase in plant density (D6.75N210) can maintain high cotton yield, while a 66.7% N reduction at 6.75 plants m–2 (D6.75N105) can only achieve high yield in the first year.  Biological yield increased with the increase of N rate and plant density, and the highest yield was obtained under 420 kg N ha–1 at 8.25 plants m–2 (D8.25N420) across the two years under investigation.  Compared to D5.25N315, N agronomic efficiency (NAE) and N recovery efficiency (NRE) in D6.75N210 increased by 30.2 and 54.1%, respectively, and NAE and NRE in D6.75N210 increased by 104.8 and 88.1%, respectively.  Soil inorganic N decreased sharply under 105 kg N ha–1, but no change was found under 210 kg N ha–1 at 6.75 plants m–2.  N deficit occurred under 105 kg N ha–1, but it did not occurr under 210 kg N ha–1 at 6.75 plants m–2.  Net photosynthetic rate and N concentration of leaves under N rate ranging from 210 to 420 kg ha–1 were higher than those under N rate of 0 or 105 kg N ha–1 at all three densities.  The findings suggest that D6.75N210 is a superior combination in cotton stubble retaining fields in the Yellow River Valley and other areas with similar ecologies.
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