The Colour of Mulching Plastic Film and Drip Irrigation Amount Combine to Affect Water and Thermal Condition in Soil and Sweet Potato Growth

Abstract

【Objective】 Plastic-film mulching combined with drip irrigation is a common cultivation method in areas facing water resource shortage, but how and if the film colour affects water and thermal condition in soil is not well understood. The aim of this paper is to fill this knowledge gap via experimental studies so as to provide technical support for crop production. 【Method】 The field experiment was conducted at Rizhao, Shandong province with sweet potato used as the model plant. We compared transparent (TM) and black (BM) plastic films, with no-mulching taken as the control (CK). Added to each mulching were three drip irrigation treatments: without irrigation (P0), irrigation with a wetting ratio of 30% (P1), and irrigation with a wetting ratio of 60% (P2). In each treatment, we measured soil temperature, soil water content, crop growth and development, and the ultimate fruit yield and quality. 【Result】 At the same irrigation wetting ratio, mulching significantly increased soil temperature in the early growth stage of the crop, but the difference between mulching and non-mulched waned as the crop grew. In contrast, when the mulching film was the same, there was no significant difference in soil temperature between different irrigation wetting ratios. On cloudy days, soil temperature in P2 did not vary as much as that in P1 and P0, and TM increased the surface soil water content more than BM and NM in the early reproductive stage of the crop. In rainy seasons, mulching enhanced surface runoff and hence reduced soil water content. There was no significant difference in soil water content between different wetting ratios when the mulching film was the same; when the irrigation wetting ratio was the same, BM had higher yield than NM and TM. When the mulching film was the same, the yield of P1 was the highest. Mulching combined with P1 significantly changed the stem diameter and vine length of the crop. It was found that mulching also significantly improved both below- and above-ground dry matter. Mulching film colour and drip irrigation wetting ratio did not affect sweet potato quality at significant level, despite the significant increase in fruit yield in BM. 【Conclusion】 Our experimental results showed that black mulching film combined with 30% drip irrigation wetting ratio gave the highest yield.

Keywords

• sweet potato
• plastic film mulch
• soil water and thermal condition
• fruit quality