The Effects of Reclaimed Water Irrigation on Growth and Quality of Alfalfa in Ningxia

Abstract

【Background】Ningxia is in arid and semi-arid region in China, characterized by uneven spatiotemporal precipitation, strong evaporation, long cold winter, short hot summer, and late arrival of spring and early onset of autumn. Over the past years the planting areas of alfalfa in Ningxia have continued to increase due to its high yield and nutrition, but water resource scarcity has constrained its production. Reclaimed domestic wastewater can be used as an alternative irrigation water source, but it is rich in salt content and other organic and inorganic contaminants, and the impact of its irrigation on growth and quality of alfalfa remains obscure. 【Objective】This paper aims to experimentally unravel the changes in growth and quality traits of the alfalfa irrigated with treated urban domestic wastewater. 【Method】The experiment consisted of three factors and three levels, all designed using the orthogonal test. The primary- and second-order factors of the irrigation that affected alfalfa growth and quality traits were calculated using the variance analysis, from which the optimal combination was proposed. 【Result】Irrigation amount impacted plant height, stem thickness, first-level branch number, hay yield, crude fat, crude fiber, acid detergent fiber, neutral detergent fiber, relative feeding value, nitrogen, phosphorus, potassium and calcium all at significant level (P<0.05). The effect of water quality on crude ash was also at significant level (P<0.05). Irrigation method and water quality did not show significant effects on other plant traits. The optimal combination of irrigation amount, irrigation method and water quality for alfalfa growth, yield and quality was A3B2C1, consistent with the references. 【Conclusion】When rainfall during the growth season of alfalfa was 113.5 mm, irrigating 2 280 m3/hm2 of water in nine times using surface drip irrigation, with each time irrigating 240 m3/hm2 of the reclaimed water, was optimal (A3B2C1). This could ensure high and quality yield while in the meantime keep heavy metal contents in the crops far less than the national standard.

Keywords

• reclaimed domestic water
• alfalfa
• irrigation technology
• irrigation schedule
• subsurface drip irrigation