摘要:环渤海低平原冬小麦夏玉米一年两作种植系统中，冬小麦季微咸水灌溉造成土壤含盐量增加，影响下茬玉米正常出苗。通过水分调控消减根层土壤盐分是有效可行的途径，并利于冬小麦夏玉米一年两作的微咸水安全利用。该研究通过盆栽与田间试验相结合的方法，研究玉米出苗对土壤水盐阈值的响应以及玉米播后灌水对出苗、生长、根层水盐和产量的影响。盆栽试验结果表明：1）玉米在低土壤盐分含量（全盐含量0.8 g·kg-1）下，60%田间持水量即可达到正常出苗；2）在高土壤盐分含量（全盐含量3.5 g·kg-1）下，出苗时间延长，出苗率降低；3）土壤盐分对出苗的影响，随着土壤含水量降低而越趋严重。因此在较高的盐分条件下，维持出苗期间一定土壤含水量，更利于缓解土壤盐分对玉米出苗的影响。大田试验中灌溉水盐分梯度为淡水（对照）、3 g·L-1、4 g·L-1和5 g·L-1。田间试验结果表明：1）随着灌溉水盐分浓度增加冬小麦收获时0~20 cm土壤盐分含量明显增加；2）淡水、3 g·L-1、4 g·L-1和5 g·L-1灌溉冬小麦，收获期0~20 cm土壤盐分含量分别为1.0 g·kg-1、1.3 g·kg-1、1.6 g·kg-1、2.0 g·kg-1；3）夏玉米播种后立即灌溉一次75 mm淡水，玉米出苗期耕层土壤含水量维持在田间持水量的70%以上，土壤含盐量下降到1.0 g·kg-1左右，夏玉米生长进程和产量不受影响。2年（2015年和2016年）淡水、3 g·L-1、4 g·L-1和5 g·L-1微咸水拔节期灌溉冬小麦，下茬夏玉米产量分别为9 510.4 kg·hm-2、9 913.6 kg·hm-2、9 910.6 kg·hm-2、9 986.0 kg·hm-2和9 621.8 kg·hm-2、9 455.3 kg·hm-2、9 460.2 kg·hm-2、9 221.4 kg·hm-2，产量差异不显著。考虑该地区降水的时间分布，与玉米生长同期的充足夏季降水的淋洗作用，微咸水灌溉小麦的积盐可得到很好淋洗。因此，该地区在冬小麦生长季实施不超过5 g·L-1微咸水灌溉，利用冬小麦夏玉米关键生育期水分调控，可消减微咸水灌溉土壤盐分积累对玉米出苗影响，结合夏玉米出苗水管理和雨季淋盐，实现周年稳产和水盐平衡，根层土壤不积盐。
关键词:冬小麦-夏玉米/
微咸水灌溉/
土壤盐分积累/
玉米出苗率/
盐分淋洗
Abstract:Winter wheat-summer maize double cropping system is the main planting pattern in the Low Plain around Bohai Sea of China, where fresh water is in serious shortage but with sufficient brackish water resources. Rational utilization of salt water resources is great significance for food safety in the area. However, brackish water irrigation of winter wheat caused salt accumulation in the upper soil which affected summer maize seedling emergence. Regulated water management was an effective and feasible way of reducing the negative effects of salinity, which was also beneficial for salt water irrigation in the double cropping system. In this study, a combination of pot and field experiments was conducted. The pot experiment consisting of 3 soil salinities[0.8 g·kg-1(low salt content), 2.3 g·kg-1(medium salt content) and 3.5 g·kg-1(high salt content)] and 4 (for low salt content, ) or 8 (for medium and high salt water content) water contents (55%-85% of field capacity) were used to test the response of maize seedling emergence to soil water and salt contents. In the field experiment, salt water with different salinities[0 (CK), 3 g·L-1 (SWT1), 4 g·L-1 (SWT2) and 5 g·L-1(SWT3)] was used to irrigate winter wheat at jointing stage to determine the effect of salt accumulation due to salt water irrigation and desalinization by irrigation/precipitation on maize growth and grain yield. The pot experiment results showed that 60% of field capacity supported normal seedling emergence under low soil salinity (0.8 g·kg-1). In high soil salinity (3.5 g·kg-1), seedling emergence was prolonged and the rate of emergence reduced. The effect of soil salinity on seedling emergence became serious with decreasing soil moisture content. Under high salinity conditions, high level of soil moisture alleviated the adverse effects of soil salinity on maize seedling emergence. Field experiment (in 2015 and 2016) results showed that with increasing salt concentration of irrigation water, soil salt content in the 0-20 cm soil layer increased significantly at winter wheat harvest period, with soil salt contents of 1.0 g·kg-1(CK), 1.3 g·kg-1 (SWT1), 1.6 g·kg-1(SWT2) and 2.0 g·kg-1 (SWT3). After summer maize sowing, an irrigation of 75 mm fresh water kept water content in the plough layer at 70% field capacity, and reduced soil salt content to 1.0 g·kg-1, which was not significantly affected the growth and yield of summer maize. Yields of summer maize were 9 510.4 kg·hm-2 (CK), 9 913.6 kg·hm-2 (SWT1), 9 910.6 kg·hm-2 (SWT2) and 9 986.0 kg·hm-2(SWT3) in 2015, and 9 621.8 kg·hm-2 (CK), 9 455.3 kg·hm-2 (SWT1), 9 460.2 kg·hm-2 (SWT2) and 9 221.4 kg·hm-2(SWT1) in 2016 under salt water irrigation of winter wheat at jointing stage. Considering the temporal distribution of precipitation and the salt leaching of sufficient summer rainfall in the same season of summer maize growth, the effect of soil salt accumulation in winter wheat season on summer maize growth was avoidable. Therefore, irrigation of salt water with less than 5 g·L-1 salinity at winter wheat jointing stage was safe for the succeeding crop, summer maize. The resonable water managements at key growth stages of winter wheat and summer maize simultaneously stabilized crops annual yield and water-salt balance under brackish water irrigation.
Key words:Winter wheat-summer maize cropping system/
Brackish water irrigation/
Soil salt accumulation/
Maize emergency rate/
Salt leaching
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