Effects of water quality and nitrogen applied on soil salinity and cotton growth under drip irrigation in arid region

Abstract

<b><sc>Abstract.</sc></b> <b>Understanding the interactions between soil salt and nitrogen is of significant importance for promoting crop growth and nitrogen uptake. To evaluate the effects of irrigation water quality and nitrogen application rate on plant nitrogen uptake and cotton growth, a pot experiment was conducted in the arid region of southern Xinjiang in 2019. Treatments included three irrigation water qualities (groundwater (GW), 1.27 g l^-1; brackish water (BW), 3.03 g l^-1 and saline water (SW), 4.70 g l^-1) and three nitrogen application rates (255 kg ha^-1, 315 kg ha^-1 and 375 kg ha^-1). Results showed that a higher irrigation water salinity resulted in a higher soil salt accumulation and a lower nitrogen uptake. The highest nitrogen application rate tested can reduce soil salt accumulation by 65% and increase nitrogen uptake rate by 24%. The plant height, leaf area index (LAI) and aboveground biomass of cotton were significantly reduced with an increasing irrigation water salinity. And the increasing nitrogen application rate alleviated the adverse effects of salinity on cotton growth to some extent. When GW or SW was used, the highest nitrogen application rate always produced the highest plant height, LAI and aboveground biomass. When BW was used, no significant difference in aboveground biomass was found between nitrogen application rate of 315 kg ha^-1 and 375 kg ha^-1. Considering soil salt accumulation, nitrogen uptake rate and aboveground biomass, a moderate nitrogen application rate (315 kg ha^-1) under BW irrigation and a high nitrogen application rate (375 kg ha^-1) under GW and SW irrigation were recommended for cotton planting in arid region.</b>