Water-heat-salt effects of mulched drip irrigation maize with different irrigation scheduling in Hetao Irrigation District

Abstract: Along with the development of Northwest Water-saving and Benefit-increasing strategy in China, mulched drip irrigation is booming in Hetao Irrigation District because of its advantage in water saving and high production. However, soil salinization has been a potential risk factor in arid area, thus enough attention should be drawn in the management of soil salt. This research studied the influence of different mulched drip irrigation schedules (lower irrigation limits were ?10, ?20, ?30 and ?40 kPa, respectively) on water and salt profile distribution characteristics, soil temperature, maize production and quality. Moreover, the salt-leaching irrigation in non-crop growth period (i.e., autumn irrigation, which is a traditional irrigation custom in Hetao Irrigation District after crop was harvested in autumn to leach salt and store the water in soil for the next year) had also been investigated. The experiment was carried out in the year of 2014-2015. The irrigation quota for each treatment was 518.0, 444.7, 368.3 and 268.3 mm, respectively. The leaching irrigation amount was 180 mm. The soil samples were collected for moisture, salinity measurements. Soil temperature was also sequentially measured during the experiment. After harvest, the maize yield and quality were determined. The results showed that the distributions of soil water and salt profiles were uneven under different mulched drip irrigation schedules. Soil salt migrated from the central mulching soil to the bare field, tending to accumulate in surface soil layer outside the film during the mulched drip irrigation. Soil temperature was influenced by air temperature, leaf area index, irrigation practice and soil moisture comprehensively. Soil temperature dropped sharply after irrigation practice, and recovered 2-3 days later. The optimum accumulated soil temperature for the nutritive growth period of maize was ?30 kPa. Salt accumulation at the depth of 0-40 cm inside the film in maize growth period was little for almost all the treatments. The treatment of ?10 kPa could leach 0-100 cm soil salinity effectively, while influence of the other treatments on the 0-100 cm soil salt was not obvious in the short term, and long-term observation to study impact of different drip irrigation lower limit on soil salt is needed. The effect of salt-leaching irrigation with 180 mm Yellow River water in non-crop growth period was remarkable, and the soil salinity decreased by 10.86%-26.14% on average, resulting in a relatively uniform salt profile at 0-100 cm. A combination of irrigation schedule for water-saving and leaching irrigation in the non-crop growth period for salt-controlling was helpful to control the salt accumulation. The maize yield was highest in the treatment of ?20 and ?30 kPa. The yield was 16 511 and 14 964.4 kg/hm2, respectively. The quality of maize was similar for all the treatments. Considering soil moisture, temperature, salinity and maize yield, we suggested that the limit of soil suction to trigger irrigation was ?30 kPa. However, due to the impacts of the frost-freeze phenomenon and particular hydrogeological condition in Hetao Irrigation District, the detailed leaching irrigation schedule to control soil salt induced by mulched drip irrigation need further investigation in the future.