Effects Of Biochar On Nutrition Of Rice In Gleyed Paddy Fields

Rice is one of the most important cereal crops worldwide, the rice planting area accounts for26.6%of China’s total cropland and the rice production accounted for43.6%of the total grain yield. With the growing population in China, the gap of required cereals is continuously enlarging, and it’s expected the total cereal production should be increased by40%to meet the food demand in2030. Improvement of medium-low yield cropland, which represented2/3of the farmland in China, is one of most important strategy for food security in China. There are3.46million hm2of gley paddy field, which accounts for44.2%of medium-low yield cropland and15.1%of the rice planting area in China. Half of gleying paddies exist in Southwest region of China, accounting for36%of the paddy fields in this area. At present, there are both of great potential and challenge to improve the productivity of gleyed paddy soils.Biochar is a byproduct of biological pyrolysising, which is a stable, highly aromatic organic matter rich in carbon and mineral elements. Recent years, biochar as a soil amendment is well studied with great progresses. However, few studies could be found to amend the gley paddy soil and rice nutrition by biochar application. Understanding the mechanism of improvement of gley paddy soil by biochar and exploring the impact of biochar application on nutrient uptake and growth of rice in greying paddies would be of theoretical and practical significance to increase rice production and maintain soil fertility in southwest China.Therefore, field trial and pot experiment were conducted to study the impact of biochar originated from rice husk on rice growth, nutrient uptake and improvement of gleization paddy soil. The results showed that the biochar application with a reasonable level could increase rice grain yield to some extent depending experimental conditions. In field condition, biochar application of1500kg/hm2increased grain yield by9.4%compared with control (without biochar application); while biochar application with0.1%of soil weight resulted in the largest increase in grain yield, which was11.8%higher than control. The major reason of yield increase was due to increasing in numbers of effective tillers, shoot biomass accumulation and thousand grain weight (TGW). However, excessive application of biochar will harm the growth of rice and resulted in low grain yield. In field condition, lodging of rice happened only in treatment with high dose of biochar application (3000kg/hm2), due to oversized rice population; and there was even no grain yield when application of biochar with5%of soil weight in pot experiment. Application of biochar to improve numbers of tillers, application of different levels of biochar could increase numbers of tillers to15%-22%in field trial, when application of biochar with5%of soil weight increased numbers of tillers by10.9%compared with treatment has not biochar in pot experiment, this n rice production. Biochar with application of different levels can increase the amount of dry matter accumulation, in field condition, biochar application of1500kg/hm2increased the highest amount of dry matter accumulation at mature stage; in pot condition, biochar application with0.1%of soil weight increased the highest amount of dry matter accumulation at mature stage; Application of biochar can certainly degree increase the total amount of rice roots and the proportion of white roots, biochar application(0.1%) resulted in the highest root activity, and more slowly the rate of aging of roots, but when the root activity was significantly lower when application biochar more than0.1%of soil weight, the root activity which application of biochar (1%and5%) are lower than without the application of biochar, thus affecting the growth and yield of rice.Biochar application promoted the absorption of Nitrogen (N), Phosphorus (P) and Potassium (K) by rice plants. The N, P, K concentration in rice plant at each growth stage had been increased to varied degrees due to application of different levels of biochar. Compared with control, the shoot N accumulation at maturity in field experiment was increased by10.0%,23.4%and12.2%with application of biochar as750,1500, and3000kg/hm2, respectively. Similarly, the P accumulation was increased by9.6%16.5%and2.9%; the K accumulation was increased by37.5%64.8%and57.1%, respectively. In pot experiment, shoot N, P and K accumulation by application of0.1%biochar was increased by8.0%,5.0%and12.3%, respectively. In addition, biochar application also increased the K uptake after flowering in field condition. The resulted showed that18.4%of total K accumulation was taken up after flowering in control treatment, whereas25.3%,28.0%and25.6%of K was taken up in treatments with applications of biochar. Improved K absorption after flowering would promote the transport of carbohydrates to developing grains and thus increase TGW.Application of biochar also affected the properties of gleyed paddy field, such as soil pH, organic matter, total nitrogen, available P and available K in both conditions. The applications of biochar significantly increased the soil pH, reducing the content of reducing substances, increasing the redox potential in0-20cm soil profile, enhance supply of available nutrient in soil,that would be helpful for the roots development, promote effective heads from tillers, absorption of nutrients, improved rice production. In addition, we observed that application with overdose biochar significantly reduced root activity, rise of pH.It will affect root growth and absorption nutrients of rice, leading to decrease in rice production.