咸淡水交替灌溉下灌水定额对土壤盐分及夏玉米生理生长指标的影响

The Effects of Alternate Saline and Fresh Water Irrigation on Soil Salinity and Physiological Traits of Summer Maize

【目的】探求适宜的咸淡水交替灌溉方式和灌水定额。【方法】以夏玉米为研究对象,设置了4种咸淡水交替灌溉方式(B0:全生育期灌淡水,对照;B1:六叶—抽雄期灌3 g/L微咸水,其余生育期灌淡水;B2:抽雄—吐丝期灌3 g/L微咸水,其余生育期灌淡水;B3:吐丝—成熟期灌3 g/L微咸水,其余生育期灌淡水)和4种灌水定额(W1:0.6E;W2:0.8ET_(c);W3:1.0ET_(c);W4:1.2ET_(c))进行避雨盆栽试验,研究了咸淡水交替灌溉方式和灌水定额对土壤盐分及夏玉米生理生长的协同调控机制。【结果】当灌水定额增至1.2ET_(c)时,咸淡水交替灌溉对土壤盐分有淋洗作用,其中B1处理淋洗效果较好,1.2ET_(c)处理0~40 cm土层平均含盐量比1.0ET_(c)处理降低了9.9%。生育期末最后1次灌水后,B0处理出现脱盐现象,其他处理均出现积盐现象,相较于处理前的0~40 cm土层,B0处理平均含盐量降低25.9%~42.6%,B1、B2处理和B3处理平均含盐量分别升高34.9%~58.5%、73.7%~110.4%和88.7%~128.7%。灌溉微咸水能降低叶片相对含水率,提高钠钾比(ω_(Na)^(+)/ω_(K)^(+)),削弱光合能力,加剧氧化应激反应,且微咸水灌溉越早影响程度越大,增加灌水定额能降低盐分胁迫对B2和B3处理的影响程度,但加剧了B1处理盐分胁迫危害,B1处理光合受阻严重,净光合速率(P_(n))和气孔导度(G_(s))较B0处理分别降低了40.5%~69.3%和32.3%~68.0%。越早使用微咸水,根干质量密度和伤流量越小,对根系生长越不利,减产幅度越大,随着灌水定额的增加,B1处理根系生长受阻更严重,产量大幅降低,而B2处理和B3处理根系生长及产量均有所改善,尤其是B3处理,产量较同等灌溉水平下B0处理仅降低了1.5%~2.0%。【结论】生育前期不宜使用微咸水灌溉,生育后期使用微咸水灌溉时适当增加灌水定额,可在实现夏玉米高产的同时降低土壤盐碱化风险。

【Background and objective】The lack of freshwater is a main limiting factor in agricultural production in northern China.As a mitigation,brackish waters including saline groundwater and treated wastewater have been tipped as a supplementary source for irrigation.Since brackish waters are rich in dissolved salts,it is critical to assess the impact of long-term brackish water irrigation on soil quality and its consequence for crop growth.The purpose of this paper is to fill this knowledge gap by systematically studying the influence of alternate fresh and saline water irrigation on soil salinity and crop growth.【Method】The pot experiments were conducted under rain-proof conditions with summer maize used as the model plant.We compared four irrigation amounts:60%(W1),80%(W2),100%(W3)and 120%(W4)of the potential evapotranspiration(ET_(c)).Saline water with concentration of 3 g/L was irrigated at the cob development-pollination stage(B1),pollination stage-kernel development stage(B2),and pollination-harvest stage(B3),respectively.For each irrigation amount,freshwater irrigation in the whole growth season was taken as the control.In each treatment,we measured soil salt content,physiological traits and ultimate yield of the maize.【Result】(1)For irrigation amount W4,alternate fresh and saline water irrigation desalinated the soil,especially B1 where the average salt content in 0~40 cm soil was 9.9%lower than that in W3.After harvest,B0reduced initial salt content in 0~40 cm soil by 25.9%~42.6%depending on irrigation amounts,while B1,B2 and B3resulted in salt accumulation with the salt content in the top 0~40 cm soil increased by 34.9%~58.5%,73.7%~110.4%and 88.7%~128.7%,respectively,compared with the initial salt content.(2)Irrigating with the saline water too early had a detrimental effect on leaves.It was found that B1 hindered photosynthesis with the net photosynthetic rate(P_(n))and stomatal conductance(G_(s))reduced by 40.5%~69.3%and 32.3%~68.0%,respectively,compared to that in B0.(3)Irrigating with the saline water too early as in B1 hampered root development thereby reducing its water and nutrient uptake,which led to a yield reduction.In contrast,delaying the saline water irrigation as in B2 and B3 only marginally comprised the yield,with the yield reduction in B3 being 1.5%~2.0%compared with the control with freshwater irrigation.【Conclusion】Irrigating summer maize using saline water at concentration of 3 g/L does not considerably compromise its yield only when implementing at its late growth stage.An appropriate increase in irrigation amount can further reduce the risk of soil salinization and achieve high yield.