Abstract:

To solve the problems of excessive application of chemical fertilizer, low crop nutrient utilization efficiency and high risks of non-point source pollution in rice production, the impacts of chemical fertilizer reduction combined with organic fertilizer on nutrient absorption, partial productivity of fertilizer, nutrient balance and rice yield were studied. The optimum management practices were identified in this study, which provided a theoretical basis for reducing fertilizer use, increasing use efficiency and improving soil fertility. A field experiment was carried out in the early rice growing season of western Guangdong in 2021. Four local recommended fertilization methods were tested, including optimized fertilization treatment (OPT), and reducing the rate of farmers’ conventional fertilizer application by 10%, 20% and 30% while applying organic fertilizer denote as OM1, OM2, and OM3 treatment, respectively. The results showed that the grain yield and grain-to-straw ratio varied from 5667-5967 kg/hm² and 1.09-1.31, respectively. The partial factor productivity of nitrogen (N), phosphorus (P) and potassium (K) fertilizer were 30.4-47.2, 96.0-122.1 and 47.2-105.9 kg/kg, respectively. The apparent balance of N, P and K were 54.2-115.3, 17.1-29.8 and 1.2-67.0 kg/hm², respectively. All of them were in a surplus state. In the treatments of organic fertilizer application, the rice grain yields, ratios of grain to stem, N, P, K fertilizer partial productivity, P absorption rate and K absorption rate increased along with the decrease of synthetic fertilizer application rate, while the apparent balance of N, P and K decreased. The straw K content and K partial factor productivity of each organic fertilizer substitution treatment were significantly higher than those of OPT treatment (P<0.05). Compared with farmers’ conventional fertilizer application, OPT, OM1, OM2 and OM3 treatments could maintain the paddy yield, and improve the ratio of grain to stem, the P content and K contents of grain and straw. Considering the ratio of grain to stem, P and K partial productivity, OM3 treatment was identified as optimum management practice. While considering the partial productivity of N fertilizer, N absorption rate, N surplus rate in soil and output-input ratio, OPT treatment was identified as optimum management practice.

Key words: paddy, synthetic fertilizer reduction, combined application of organic and synthetic fertilizers, yield, nutrient utilization