Improvement of Fertilizer N Recovery by Allocating More N for Later Application in Cotton (Gossypium hirsutum L.)

In the Yangtze River Valley in China, 300 kg N/ha is normally applied to cotton crops in three splits: pre-plant application (PPA, 30%), first bloom application (FBA, 40%) and peak bloom application (PBA, 30%).However, low plant fertilizer N recovery (FNR) (30-35%) was accompanied with the negative effects on the environment.Two-year field trial has proven the feasibility of obtaining the same cotton yield by allocating more N for later application (PBA) with lower N rate.A pot experiment was carried out to testify if there was any improvement in N absorption and FNR in cotton (Gossypium hirsutum L. cv Huazamian H318) plants by fixing 40% of 225 kg 15 N/ha for FBA.The results showed that both total N and fertilizer 15 N accumulation in cotton plants responded positively to N split ratio resulting in a (curve) meeting point at 80 DAE (days after emergence).The total N and fertilizer 15 N amount (mg/plant) increased from 1526 and 1194 to 2143 and 1924, respectively, as the ratio of N allocated to PBA increased from 20% (N42) to 60% (N06).Cotton plants absorbed N the most during flowering, but N06 had the highest 15 N uptake rate (mg/plant/d) (33) during boll setting, which was almost the same as that during flowering; whereas N42 dropped drastically to 5