Abstract
Controlled drainage (CD) is an important agricultural measure for maintaining soil moisture and nutrients, controlling groundwater level, and increasing crop yield. In arid regions, CD can be used to improve the water supply in agriculture and reduce environmental pollution. In this study, we investigated the effects of CD, including drainage depths of 40 cm (CWT1) and 70 cm (CWT2) during the plant growth stages, free drainage (FD), and open-ditch drainage (OD), on the migration of water, nutrients, and salts in the soil, the dynamics of the groundwater level, the loss of soil nitrogen, and the growth of oilseed sunflower plants. Compared with FD, CD increased the water and nutrient content in the soil, reduced nitrogen loss, and enhanced the ability of the soil to continuously supply nitrogen to the oilseed sunflower plants, which benefited plant growth at later growth stages and reduced environmental pollution. During the period between irrigation at the budding stage and the harvest stage, the average soil water content in the 0–20 cm soil layer in CWT1 increased by 3.67%, 4.78%, and 0.55%, respectively, compared with that in CWT2, FD, and OD. The soil mineral content in CWT1 was 25.17%, 35.05%, and 17.78% higher than that in CWT2, FD, and OD, respectively, indicating that higher soil salinity occurred at the later stage of plant growth in CWT1, which actually had little effect on the plants due to their enhanced salt tolerance and increased need for water and nutrients at that stage. In addition, CD delayed the decline in groundwater level, which allowed the plants to use groundwater at later growth stages, and as a result, the yield and water-use efficiency were improved. CWT1 significantly increased oilseed sunflower yield by 4.52–11.14% and increased water-use efficiency by 1.16–10.8%. Moreover, CWT1 also increased the survival rate of the oilseed sunflower plants by 2.62–2.92%, and the plants demonstrated good growth. Therefore, under CD conditions, plants used soil water and nitrogen more efficiently and, as a result, their productivity was increased, and the water quality was improved.
Highlights
We aimed to examine the effects of different drainage systems on soil water content, salinity, mineral nitrogen content, and the quality of drainage water, to understand the regularity of the response of the soil–crop–environment system to drainage methods, and to determine the best drainage system for benefiting crop yield, reducing environmental pollution, and improving water- and fertilizer-use efficiency
CWT1, CWT2, and free drainage (FD) all had drainage pipes concealed beneath the 100 cm soil layer, and the difference in soil water content between them was small
After irrigation at the budding stage, due to the 40 cm drainage depth, CWT1 discharged less water from the soil during the plant growth stages compared with the other drainage systems, thereby providing better water and fertilizer conditions for the growth of plants at their later growth stages
Summary
Controlled drainage has a long history of use and is widely applied globally [1,2,3,4]. In arid and semi-arid regions, soil salinization can be prevented by drainage. In humid and semi-humid regions, excessive water can be drained away to reduce the risk of yield loss, allowing farmers to cultivate a greater variety of crops. Drainage facilitates the reclamation of flood-stricken areas and provides better growth conditions for crops [5]. Surface drainage causes an increase in agricultural production, but in many countries, it leads to a reduction in retention and water loss, and it is ineffective in the event of a flood. The advancement of science and technology and the increasing attention to agriculture have encouraged the wide application of subsurface
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