Influence of mulches on urban vegetation construction in coastal saline land under drip irrigation in North China

Abstract

In order to generate information for reclaiming coastal saline sandy-loam soil for urban vegetation construction around Bohai Bay in North China, a field experiment combined with drip irrigation and setting a gravel–sand layer beneath the saline soil but above the water table was conducted to study the effect of mulches on irrigated water amount, soil salt control and willow (Salix babylonica L.) growth, and construction costs were also estimated during 2012 and 2013. The three mulch treatments were control treatment with no mulch (C1), black shading net mulch (C2) and straw mulch (C3). In order to leach salts in the soil profile, irrigation was triggered by the soil matric potential threshold at 20-cm soil depth of −5kPa in the early stage, and this was changed to −10kPa until the end of the first growing year, and to −20kPa for the second year. The results showed that (1) the straw mulch consumed the least irrigation water, followed by the black shading net mulch and the control treatment. Compared to the control treatment, the amount of irrigation for the straw mulch had decreased by 12% in 2012 and 27% in 2013. (2) The salinity reduction was mainly related to rainfall and the strategy of drip irrigation; and the mulches, especially straw mulch, decreased the risk of salt accumulation in early spring. (3) The best growth characteristic of plants and the optimal investment cost were for straw mulch, and the high investment cost in 2012 was due to soil preparation cost and the willows, gravel and sand cost was high and then it had decreased by 90% in 2013. From the combined points of water saving, plant growth and investment cost, the use of straw mulch with drip irrigation could aid in urban vegetation construction on coastal saline land in North China.