灌水频率对辣椒各生育期设施土壤盐分迁移规律的影响

为寻求设施栽培条件下辣椒各生育期适宜灌水频率,通过室内土箱模拟试验,研究辣椒苗期、现蕾期和成熟期同一灌水总量高(5 d灌1次水)、中(10 d灌1次水)和低(15 d灌1次水)3个不同灌水频率设施土壤剖面盐分迁移规律。结果表明:辣椒苗期,各灌水频率灌水后,0~20 cm土层脱盐率均达34%以上,积盐量降幅分别达47.57%、49.85%和52.41%,20~50 cm土层积盐量却表现为中频低频和高频;辣椒现蕾期,灌水前,中和低频灌水土壤含盐量最大值均出现在10~20 cm土层,而高频灌水最大值在30~40 cm土层,灌水后高频灌水由于优先流导致30~40 cm土层含盐量降幅最大;辣椒成熟期,灌水前,高和低频灌水盐分表聚现象强于中频,但高频灌水后,0~20 cm土层脱盐率仍相对较大,20~50 cm土层盐分有累积优势,中频灌水下20~50 cm土层含盐量降幅却较大,20~50 cm土层积盐量高频灌水比中频灌水高18.86%。在辣椒成熟期前采用中频适量灌水较优,但在辣椒成熟期宜采用高频少量灌水,低频大量灌水易出现将大量盐分离子淋洗出土体的现象,加大地下水的污染风险。

Effect of irrigation frequency on migration regularity of greenhouse soil salt during different growth stages of pepper

Abstract: Horticultural production has been widely used in China, and produces high social and economic benefits as a new model of rural industry. However, mismanagement of irrigation and fertilization in greenhouse vegetables, resulting in the nutrients enrichment in surface soil profile through evaporative water loss is an important reason for greenhouse soil salinization, which makes the greenhouse soil unsuitable for sustainable use. Soil salinization negatively impacts agricultural productivity, environmental health, and economic welfare. In order to find a proper irrigation frequency for each growth stage of pepper cultivated in greenhouse, simulated experiments of soil box in a laboratory were carried out to investigate the migration mechanisms of greenhouse soil salt during seedling, squaring, mature stage of pepper with different irrigation frequencies (irrigation every 5, 10, 15 days) as well as the same amounts of irrigation. The results indicated that the different irrigation frequency treatments played an important role in salt leaching. At the seedling stage of pepper, Soil salt distribution in soil profile was uniform at seedling stage of pepper in each irrigation frequency, and there was a significant surface convergence phenomenon occurred before irrigation, the zone with the highest value of soil salt for each treatment was at a depth of 0-10 cm. Salts were moved downward with water, the soil salt content changed in the entire profile with treatment progress, the desalinization rates of 0-20 cm soil layer decreased by 33.97%-66.20%, 35.96%-67.36%, 37.94%-67.94%, respectively under high, middle and low irrigation frequency, meanwhile, the ratio of desalinization increased with the decreased irrigation frequency, the salt accumulation decreased by 47.57%, 49.85% and 52.41% with different irrigation frequencies after irrigation. The salt accumulation of 20-50 cm soil layer with the middle irrigation frequency was greater than that of high and low frequency. At the squaring stage of pepper, the maximum salt contents with the irrigation frequency of middle and low frequency before irrigation were observed in 10-20 cm soil layer, and that with the high irrigation frequency was noticed in 30-40 cm soil layer. Salt content in 30-40 cm soil layer decreased most in response to the preferential flow with the high irrigation frequency after irrigation. The results indicated that soil salt transportation were influenced by preferential flow, it is obvious that there showed a phenomenon of preferential flow at squaring stage of pepper under high frequency. Besides, at the mature stage of pepper, the salt accumulation in soil surface with the high and low irrigation frequency were more than that with the middle irrigation frequency before irrigation. After irrigation, the desalinization rate in 0-20 cm soil layer with the high irrigation frequency remained large and there was a preponderance of soil salt accumulation in 20-50 cm soil layer. The salt content decreased largely in 20-50 cm soil layer with the middle irrigation frequency. Salt accumulation in 20-50 cm soil layer with the high irrigation frequency was 18.86% greater than that with the middle irrigation frequency. Soil salt transportation were influenced by preferential flow, it is obvious that there showed a phenomenon of preferential flow at squaring stage of pepper under high irrigation frequency treatment, and which occurred at mature stage of pepper under middle irrigation frequency treatment. These results indicated that the better irrigation should be with appropriate amounts and middle irrigation frequency before the mature stage of pepper, while that should be with small amounts and high frequent irrigation during the mature stage of pepper. The large amounts and low frequency irrigation can easily cause serious salt leaching in soil profile and even groundwater pollution.