Negative pressure irrigation for greenhouse crops in China: A review

Abstract

Negative pressure irrigation (NPI) has potential to reduce evaporative loss of water on –the soil surface, reduce runoff and maintain a stable soil water content, as compared to other irrigation methods. However, there is a lack of synthesized information in literature with regard to its effects on crop yield and water use efficiency (WUE), which hinders its wide adoption in China. We introduce the principles and device of NPI, analyze the NPI research hotspots and review its effects on yield and WUE of typical greenhouse crops, based on the literature available in the China National Knowledge Infrastructure (CNKI) and Web of Science (WOS). Review shows that a NPI device typically consists of emitter, water pipe, water storage tank and negative pressure generator. The material of emitters is important in affecting irrigation efficiency, and polyvinyl formal materials have higher cumulative infiltration per unit area and faster soil water movement than ceramic head under the same water pressure, as the polyvinyl formal material can control the larger soil water space than a ceramic head. Current research hotspots include the development of NPI devices, crop response and water use efficiency of NPI, and influences of environmental factors on irrigation efficiency. Compared with conventional irrigation, NPI is more energy-saving and water-saving, and significantly improves WUE and crop yield. Soil texture is the main factor contributing to the maximum vertical wetting distance and maximum horizontal wetting distance and cumulative infiltration, and it affects the irrigation efficiency of NPI and the arrangement of NPI for meeting crop water need. Results suggest that when the negative pressure level of −10 kpa to −5 kpa and the soil water content of 60–80% field capacity are most conducive to the growth of most greenhouse crops, with better agronomic effects than conventional irrigation.