In order to provide scientific theoretical basis for green manure utilization and nitrogen fertilizer application in southern rice

based on the field localization experiment in 2016

the influence of different nitrogen application rates (N0:no nitrogen application; N50:50% reduction in nitrogen; N100:conventional nitrogen; N150:50% increase in nitrogen application) on yield

nutrient uptake characteristics and nitrogen efficiency of double-cropping rice were explored in the two modes of fallow (F) and green manure (G). The results showed that compared with the fallow mode

the green manure mode of winter planting increased the yield of early and late rice under these four different nitrogen levels

and the yield of early and late rice increased by 8.0% and 5.7% on average. In both modes

the yield of early rice increased firstly and then decreased with the increase of nitrogen application

while the increase of late rice showed an upward trend. The green manure model of winter planting also increased the accumulation of nitrogen (N)

phosphorus (P)

and potassium (K) in the aboveground part of the plant and the partial productivity of nitrogen fertilizer. With the increase of nitrogen application

the nutrient harvest index and nitrogen fertilizer utilization rate of early and late rice in these two modes mostly showed a downward trend

and the high-level nitrogen fertilizer treatment (N150) reduced the accumulation of aboveground K elements in the early rice season. There was a significant positive correlation between early and late rice yields and N

P and K accumulation

and the decrease of high nitrogen treatment (N150) K uptake in the two modes was associated with the decline of early rice yield. Comprehensive consideration combined with the fitting analysis of rice yield and nitrogen application rate

nutrient absorption

and utilization

etc.

the suitable application range of nitrogen fertilizer in early rice season was 150.0 to170.3 kg/hm2 under the fallow mode

and 75.0 to 122.8 kg/hm2 in early rice season under winter green manure mode. Therefore

in the double-cropping rice area of southern China

planting green manure in winter can increase the absorption of N

P

and K elements in rice

and can reduce nitrogen fertilizer without reducing the yield of double-cropping rice in the early rice season

which is of practical significance for achieving efficient rice production.