Abstract:
Objective Yield and N-uptake of cotton plants in response to N applications and factors affecting the reaction were quantitatively analyzed with documented database.
Method Meta analysis was conducted on 43 relevant articles published from 2002 to 2019 to compare the effects of the planting time, area, and N fertilization as well as the soil type, density, organic matters, total N, alkali-hydrolysable N, available phosphorus, and available potassium on the yield and N-uptake of cotton plants with those without any N application.
Result The increase of 36% on yield and 51% on N-uptake of the cotton plants in 2008–2013 were significantly higher than 20% and 34%, respectively, in 2002–2007 or 28% and 33%, respectively, in 2014–2019. Increased N application promoted both yield and N-uptake of cotton plants more from the first data collection period to the second period than from the second to the last 5 years. Cotton yield and N-uptake were significantly higher with N application 300–450 kg·hm−2(38%, 58%) than N application more than 450 kg·hm−2(30%, 54%) or less than 300 kg·hm−2 (27%, 31%). There were regional variations on the effects as well. For instance, in northwest China, the fertilization resulted in the greatest increase on yield at 45% but the least on N-uptake at 35%, whereas the least on yield at 25% and the greatest on N-uptake at 65% in central China and the medium on yield at 33% and N-uptake at 38% in eastern China were observed. Increases on planting density tended to reduce the cotton yield and N-uptake. Soil type also affected the yield and N uptake as they increased significantly more in clay soil (40% and 56%, respectively) than in sandy loam (25% and 28%, respectively) and loam (36% and 39%, respectively). Grown on soil containing organic matters more than 15 g·kg−1, alkali-hydrolyzable N in the range of 50–100 g·kg−1, available phosphorus between 15–30 mg·kg−1, and available potassium greater than 300 mg·kg−1, the cotton yield was higher than without N application. And the soil containing organic matters in the range of 10–15 g·kg−1, total N more than 1.6 g·kg−1, alkali-hydrolyzable N higher than 100 g·kg−1, available phosphorus between 15–30 mg·kg−1, and available potassium less than 200 mg·kg−1 produced higher cotton N-uptake than without N fertilization.
Conclusion Application of 300-450 kg·hm−2 of N fertilizer on the filed appeared to be critical for high cotton yield.