Can shallow-incorporated organic mulching replace plastic film mulching for irrigated maize production systems in arid environments?

Since the ridge-furrow farming with plastic film mulching has caused widespread environmental pollution in maize field, it is essential to explore a substitutive strategy to mitigate plastic residue pollution while the output remains unchanged. This study aimed to investigate the potentials of shallow-incorporated organic mulching in replacement of polyethylene film mulching regarding maize productivity maintenance and its driving mechanism. Two-year (2019–2020) field experiment was conducted in an arid irrigation site of northwest China. There were five mulching treatments as follows: 1) shallow-incorporated maize straw piece incorporating into soils across 10-cm depth; 2) living clover mulching; 3) plastic film mulching; 4) combined plastic film mulching and shallow-incorporated maize straw piece and 5) combined plastic film and living clover mulching. Conventional planting without mulching was the control. For each plot with straw pieces, maize straws were cut into small pieces by straw crusher, evenly spread on soil surface and incorporated into soils using rotary tiller. Shallow-incorporated organic mulching treatments, including straw mulching and clover mulching, substantially promoted maize water productivity by 29.9% in straw mulching and 14.4% in clover mulching respectively, compared with the control. They achieved similar productivity level as plastic mulching or dual mulching treatments did. Both straw mulching and clover mulching also prolonged crop growth cycle by 10–20 days, and elevated soil temperature from the middle to late growing stage, relative to the plastic-involved treatments. Moreover, they significantly reduced field evaporation and accordingly promoted soil water storage, maintaining relatively fine hydro-thermal status. Particularly, both straw decomposition and clover biological nitrogen fixation contributed to more nitrogen input into soils at maturity. This resulted in a steady nitrogen accumulation into soils for rapid recovery growth at the later stage, i.e. excessive compensation for insufficient growth at the early stage (over-compensatory effect). Critically, shallow-incorporated organic mulching harvested higher net economic benefit by 3.3% in sole straw mulching and 10.4% in sole clover mulching relative to sole plastic film mulching respectively, while dual plastic and organic mulching decreased economic and ecological benefits. Shallow-incorporated organic mulching can obtain similar water productivity and economic benefit as polythene film mulching, as a result of over-compensation and biological nitrogen input into soils at late growing season. Polyethylene film mulching was not indispensable, and organic mulching may act as a green solution to displace film mulching according to local irrigation scheduling in arid irrigation region. ● Shallow-incorporated (10-cm) organic mulching with straw & living clover was tested. ● Organic mulching promoted soil hydro-thermal status and nitrogen input in arid irrigated field. ● Organic mulching led to similar crop yield as plastic film mulching with same irrigation amount. ● The mechanism was over-compensatory effect at the later stage in organic mulching. ● Such organic mulching might replace plastic film mulching in arid irrigation site. [ABSTRACT FROM AUTHOR]