Effects of water and nitrogen fertilization on root growth of cotton under drip irrigation in mildly salinized soil
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DOI:10.7606/j.issn.1000-7601.2019.06.30
Key Words: water nitrogen regulation  cotton  root morphological parameters  root spatial distribution  mild salinized soil  drip irrigation
Author NameAffiliation
LI Wenhao Shihezi University, School of Hydraulic Engineering, Shihezi, Xinjiang 832000, China
Key Laboratory of Modern Water-saving Irrigation Crops, Shihezi University, Shihezi, Xinjiang 832000, China 
WANG Zhenhua Shihezi University, School of Hydraulic Engineering, Shihezi, Xinjiang 832000, China
Key Laboratory of Modern Water-saving Irrigation Crops, Shihezi University, Shihezi, Xinjiang 832000, China 
ZHU Yankai Shihezi University, School of Hydraulic Engineering, Shihezi, Xinjiang 832000, China
Key Laboratory of Modern Water-saving Irrigation Crops, Shihezi University, Shihezi, Xinjiang 832000, China 
MA Dongqing Shihezi University, School of Hydraulic Engineering, Shihezi, Xinjiang 832000, China
Key Laboratory of Modern Water-saving Irrigation Crops, Shihezi University, Shihezi, Xinjiang 832000, China 
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Abstract:
      In order to explore the effects of different water and nitrogen combinations on root growth of cotton under drip irrigation in mildly salinized areas, this experiment coupled water and nitrogen under mild salt stress to determine the reasonable combination of water and nitrogen for cotton cultivation in mildly salinized cropland. We used ‘Nongfeng 133’, a local main cotton variety, to carry out a two-factor and three-level barrel cultivation experiment under mild salt stress (4~5 g·kg-1) and drip irrigation conditions. The effects of three nitrogen levels and three water levels on root growth of cotton under drip irrigation were studied. Three urea rates with nitrogen levels of 300, 600 kg·hm-2 and 900 kg·hm-2 were labeled as N1, N2, and N3, respectively, and three irrigation levels of 2 750, 3 750 kg·hm-2 and 4 750 m3·hm-2 were labeled as W1, W2, and W3, respectively. The results showed that under mild salt stress, the interaction between irrigation and nitrogen had significant effects on root surface area and average root diameter. Both root surface area and average root diameter decreased with increasing irrigation quota or nitrogen application. The effects of irrigation and nitrogen application rate on root volume of cotton in 0~20 cm soil layer were not significant. Under the condition of drip irrigation in mild salinized soil, the root surface area, average root diameter, and root volume of cotton were mainly distributed in the soil layer of 0~30 cm, and decreased gradually with the increase in soil depth in the vertical direction. In the horizontal distribution, roots were mainly distributed under the emitters. It was beneficial to the growth of cotton root system under drip irrigation of mild salinized soil when the irrigation quota was 3 750 m3·hm-2 and the urea application amount was at 600 kg·hm-2, and the cotton yield achieved the highest, 5 854.5 kg·hm-2, under this condition.