Plastic Mulching Combined with Fertilizer Affects Crop Light Interactions, Soil Temperature, and Maize Yield in Agroforestry Systems

Agroforestry systems (AFS) have been realized as a sustainable alternative for food production to adopt climate warming, but a quantitative analysis of the radiation use mechanism of converted farmland from previous desert grassland is missing. Thus, this study aimed to assess the dynamics of interception and absorption of photosynthetically active radiation (fIPAR and fAPAR), intercepted and absorbed radiation use efficiency (RUEi and RUEa), growth and productivity of spring maize grown in AFS. A two-year field experiment was conducted using a factorial combination of two fertilization levels (high and low) and three plastic film mulching (PM) (transparent film, black film, and no film). The observed parameters were: leaf area index (LAI), relative chlorophyll content (SPAD), canopy light use characteristics (fIPAR and fAPAR), soil temperature and maize productive performance. We calculated RUEi and RUEa, and quantified the contribution of light use characteristics and net photosynthetic rate (A) to yield. The results showed that fIPAR and fAPAR increased by 3.4–22.2% and 3.4–14.7% in transparent film mulching (TM) and 3.3–15.7% and 3.3–10.6% in black film mulching (BM) from jointing to grain-filling, respectively, relative to no mulching (NM). Nitrogen application positively affected fIPAR and fAPAR. And, we developing an empirical regression function to calculate the canopy fAPAR. The increased soil temperatures under PM advanced crop development. PM improved LAI, SPAD, A and prolonged the grain-filling duration. TM and BM increased RUEi by 11.7% and 4.4% and RUEa by 12.0% and 3.6% relative to NM, respectively. fIPAR and fAPAR had higher proportional contributions to yield than A, which both decreased slightly with increasing nitrogen application. LAI positively correlated with fIPAR, fAPAR, RUEi and RUEa, which were positively correlated with yield. Thus, TM combined with high nitrogen is recommended to produce high yields and resources use efficiency by maintaining high LAI.