Abstract:
A field experiment was carried out in order to explore the winter irrigation on cotton field in arid region.Influences of winter irrigation pattern and irrigating water quota for cotton field in northern Xinjiang on soil water and salt distribution as well as cotton growth and yield in the next year were discussed.From October in 2013 to October in 2014, Key Corps Laboratory for Modern Water saving Irrigation of Shihezi University, carried out the field experiment.Field without winter irrigation was taken as the control group(CK).The winter irrigation experiment set a total of 9 test groups, including 2 irrigation patters (drip irrigation and flood irrigation) and 4 irrigation water quotas: DI-1800(drip irrigation, irrigation quota of 1 800 m3/hm
2), DI-3000(drip irrigation, irrigation quota of 3 000 m3/hm
2), DI-2400(drip irrigation, irrigation quota of 2 400 m3/hm
2), DI-3600(drip irrigation, irrigation quota of 3 600 m3/hm
2), FI-1800(flood irrigation, irrigation quota of 1 800 m3/hm
2), FI-3000(flood irrigation, irrigation quota of 3 000 m3/hm
2), FI-2400(flood irrigation, irrigation quota of 2 400 m3/hm
2), and FI-3600(Flood irrigation, irrigation quota of 3 600 m3/hm
2).We used soil drilling and drying method to measure soil moisture content, and electric conductivity method to measure soil salt content, and we observed and measured the cotton growth situation for each treatment and growth stage to determine population physiological index.Dynamic changes of water and salt in 0~300 cm soils before sowing, rate of emergence, population physiological indices(leaf area duration, net assimilation rate, and leaf area index) and cotton yields in the next year of all testing groups were monitored and compared.When comparing the effect of irrigation, we found water spread and infiltrated evenly under drip irrigation situation, the infiltration speed was slow, and the water retention effect was considerably good; under the circumstance of flood irrigation, the irrigation speed was fast, the infiltration was uneven and waterlogging occurred in the cultivation layer.Results showed that winter irrigation had certain impact on water and salt content and distribution in soil profile before sowing in the next year.For both flood irrigation and drip irrigation, the influence of irrigation on water and salt contents was intensified with the increase of irrigation water quota.Winter irrigation could leach and reduce salt contents in superficial soils.Salt distribution in soil profile(especially 0~150 cm soils) before sowing was greatly influenced by winter irrigation.Due to the strong leaching effect of winter irrigation on soil salt content, it could provide good water and salt environment for crop growth.Compared to flood irrigation, drip irrigation provided more uniform and regular water infiltration.Drip irrigation in winter had an important role on cotton growth and yield in the next year.Difference of population indices between testing groups and CK increased with the increase of irrigation water quota.Appropriate irrigation water quota could increase the rate of cotton emergence in the next year and improve the population indices in early period significantly.Under winter drip irrigation with the quota of 3 000 m3/hm
2, the cotton canopy photosynthetic potential, group net assimilation rate and leaf area index improved respectively by 34.30%, 19.23% and 42.60% compared with those without winter irrigation treatment, and the photosynthesis potential and leaf area index reached peak value 10 days in advance.The leaf area index peak under 3 000 m3/hm
2 drip irrigation was 10 d earlier than CK and higher than that under the flood irrigation.Winter irrigation also could increase cotton yield in the next year.The cotton yields under 3 000 and 3 600 m3/hm
2 drip irrigation were 10.66% and 12.36% higher than that under the CK.Based on the comprehensive considerations to the effect of winter irrigation pattern and irrigation water quota on soil water and salt distributions as well as cotton growth and yield in the next year, this paper concludes that 3 000 m3/hm
2 drip irrigation is the optimum one.It can not only leach soil salts as deep as 300 cm, but also contribute a high yield, reaching 6 107.75 kg/hm
2.