Effects of co-situs application of polymer-coated fertilizers on grain yield, root distribution and soil residual N_min in summer maize

A field experiment was conducted to study effects of co-situs application of polymer-coated fertilizers(PCF)on the summer maize grain yield, root distribution, and the Nmin residual in soil profile. Before the maize sowing, the polymer-coated fertilizers were applied in the top-soil with a 4-8 cm depth, which just under the seed point. The amount of applied coated-fertilizers was N 180 kg/ha for the treatment PCFN1, and N 120 kg/ha for the treatment PCFN2. A conventional fertilizer treatment that received N 180 kg/ha and a CK treatment that received no N were included. The main results were as follows: 1)No negative impacts on seed generation and seedling growth occurred from the treatments with single co-situs application of coated-fertilizers; 2)The maize grain yields from N fertilized treatments were significantly increased, which were 9.61 to 10.4 t/ha higher than the CK treatment(8.71 t/ha). The yield from the PCFN2 treatment was same to that from conventional fertilizer treatment; 3)In the plough layers(0-30 cm), root length density in the area of 0 to 10 cm near the stem from PCFN1 or PCFN2 treatments accounted for 59%-64% of the total root, which were higher than those from conventional fertilizer or CK treatments; 4)There was no significant increase of accumulation of residual Nmin in the PCFN2 treatment compared to CK treatment; Nmin in the 60-90 and 90-120 cm layers from the conventional fertilizer or PCFN1 treatments were significantly higher than that of CK treatment after maize harvest. Taking maize yield, root distribution and N leach risk into consideration, the co-situs application of polymer-coated fertilizers with N 120 kg/ha was the best for summer maize in this experimental area.