Plastic-film mulch affects partitioning of maize biomass and nutrients to grain

Plastic-film mulch significantly improves maize (Zea mays L.) productivity in hydrothermally limited areas, but there is a lack of understanding of how mulch affects the partitioning of dry matter and nutrients to grain. This study was conducted to investigate the effects of plastic-film mulch on the remobilization of biomass and nutrients accumulated in the presilking stage to grain during the grain-filling period. A 2-yr field experiment was conducted with five maize hybrids in a cold semiarid environment. The vegetative biomass in all cultivars at maturity was generally greater than that at silking regardless of whether the soil was mulched or not, indicating that there was no translocation of presilking assimilates to the grain. The increased grain yield in plastic-film mulched plots compared with those that were nonmulched was ascribed to their enhanced partitioning of postsilking assimilates to grain. Conversely, increased accumulation of nitrogen and phosphorus in grain at maturity under mulch relative to no mulch mainly was due to increased remobilization from presilking vegetative organs. The benefit of plastic-film mulch in increasing the partitioning of postsilking assimilates and the remobilization of nutrients from presilking vegetative organs was greater in a drier than in a wetter year. The results of this study strongly support the conclusion that in hydrothermally limited environments, maize generally does not remobilize presilking assimilates but does remobilize presilking nitrogen and phosphorus in vegetative organs to the grain during grain filling. Further, plastic-film mulched, relative to nonmulched, maize increases the translocation to the grain of postsilking assimilates and presilking nitrogen and phosphorus accumulated in vegetative organs.