Effects of the Plastic Mulching System and Fertilizer Application on the Yield of Tartary Buckwheat (Fagopyrum tataricum) and Water Consumption Characteristics in a Semi-arid Area

Although plastic film mulching is commonly utilized to enhance crop water use efficiency (WUE) in semi-arid areas, the combined effect of plastic film mulching and fertilizer application on Tartary buckwheat yield is still unknown. To address this gap, a four-year field experiment was conducted from 2018 to 2021 to investigate the effect of plastic film mulching and fertilizers on the soil water storage, plant growth, yield, and WUE of Tartary buckwheat in semi-arid environments. The treatments comprised traditional planting without fertilizer (TNF), traditional planting with fertilizer application (N–P2O5–K2O: 40–30–20 kg ha−1) (TF), plastic film mulching with fertilizer application (N–P2O5–K2O: 40–30–20 kg ha−1) (MF), and plastic film mulching without fertilizer (MNF). The results indicated that MF treatment significantly increased leaf area index and SPAD values compared to the other treatments. The yield of Tartary buckwheat under the film mulching increased by 23.3% in comparison to no-mulching treatments, and under fertilizer application it increased by 18.2% compared to no fertilizer. WUE under film mulching exhibited an increase of 3.1% in 2018, 34.9% in 2019, 45.5% in 2020, and 34.6% in 2021, respectively, compared to no mulching. The impact of film mulching on WUE was more significant in years with lower precipitation compared to those with normal or higher precipitation levels. Overall, MF significantly enhanced both the yield and WUE of Tartary buckwheat. This approach proved to be an effective strategy for bolstering drought-resistant yield and optimizing resource efficiency in Tartary buckwheat cultivation in semi-arid regions. Moreover, the positive effects of plastic mulching and fertilizer application on grain yield and water use efficiency were more pronounced in drier years.