Nutritional quality degradation: A potential risk due to nutrient dilution effects in film-mulched maize

Abstract

The nutritional quality of crops is sensitive to the planting method and fertilization rate, especially in fields threatened by drought and nutrient deficiencies. Ensuring that the nutrient content of crops is adequate is important in addition to obtaining a high yield in the current agricultural production in China. Thus, a field experiment with two typical mulch planting methods (full plastic film mulching, RFF; half plastic film mulching, RFH) and five fertilization rates (N 0 +P2O5 0 kg ha−1; N 117 +P2O5 59 kg ha−1; N 173 +P2O5 87 kg ha−1 N 229 +P2O5 115 kg ha−1; N 285 +P2O5 143 kg ha−1) was conducted from 2014 to 2016 in a semiarid region, China. The potential effects of film mulching on maize nutritional quality and the differences under different fertilizer rates were studied. The results showed that RFF improved soil water and temperature conditions, and significantly increased the maize grain yield (by 17.2–38.0%) and nutrients uptake (by 14.0–22.3% in nitrogen, 24.8–35.2% in phosphorus) compared with RFH. However, the nutrient contents of plant organs decreased to different extents under RFF compared with RFH, indicating a "dilution effect". In particular, the grain nutrient content decreased by up to 3.6% for nitrogen and 6.5% for phosphorus with fertilization up to N 160 +P2O5 80 kg ha−1, but with an increasing tendency above this rate. In addition, fertilization significantly increased the maize grain yield and nutrient content, but both did not increase significantly above N230 + P2O5115 kg ha−1, and the NUE gradually decreased, especially nitrogen under RFF. Thus, RFF significantly improved the maize yield and nutrients uptake compared with RFH, but there was a risk of nutritional quality degradation, and surprisingly, this effect can be adjusted or even avoided by changing the amount of fertilizer applied. For example, in the study region, both the maize yield and quality of RFF were improved compared with RFH in the fertilization range of N(160−230)+P2O5(80−115) kg ha−1.