Effects of different ameliorant measures on the chemical and physical properties of soil in acid sulfate paddy field and rice yield

【Objectives】 Based on the current strong acidity, low available P content, high toxicity of available Al, and poor texture of acid sulfate soil, effects of different ameliorant measures were investigated on the improvement of soil physic-chemical properties and increase of rice yield in acid sulfate paddy field, so as to providing a theoretical basis for reasonable application of ameliorant, improving soil fertility, and restoring soil production capacity.【Methods】 A three-year field experiment was conducted in acid paddy soil, seven treatments were included in the experiment: no fertilizer (CK1), compound fertilizer special for rice (CK2), NK+ calcium-magnesium-phosphate fertilizer(CaMgP), NK + ground phosphate rock(GPR), compound fertilizer special for rice + lime(LIME), compound fertilizer special for rice + fly ash(FLA), and compound fertilizer special for rice + bio-organic fertilizer(BOF). The rice yield, soil acidity and nutrients, aggregate, and humus composition were determined.【Results】 After three years’ successive treatments, the average yields were increased significantly by 38.78%-75.00% in early rice and 38.31%-56.75% in late rice, compared with CK1, and increased by 9.15%-26.10% in early rice and 5.71%-13.33% in late rice, compared with CK2. The treatments of LIME, FLA and BOF had higher rice increase rates than the treatments of CaMgP and PGR did. The soil pH, the contents of available P and available K increased while the contents of exchangeable H+, exchangeable Al3+ and available SO2+4 decreased notably in the treatments added with ameliorants. Compared with CK1 and CK2, the ratio of water stable aggregate larger than 5 mm in size to the total aggregate went up markedly, and those of the aggregate of 2-1 mm, 1-0.5 mm and 0.5-0.25 mm in size decreased. Addition of FLA and BOF facilitated the formation of water stable aggregate higher than 0.25 mm in size and their stability, thereby, the percentage of aggregate destruction in the two treatments was decreased to 14.11% and 16.99%, respectively. Compared with CK1, the soil organic carbon content reduced slightly in the treatment of LIME, but increased in the other treatments. Also, application of fertilizer facilitated the improvement of the contents of carbon from humic acid and humin, reduced those from fulvic acid. Compared with CK2, CaMgP and BOF treatments obviously improved the total organic carbon content in soil, while FLA and BOF treatments raised the contents of water soluble carbon and carbon from humic acid. Compared with CK1, the HA/FA ratio increased by 16.44%-47.69% in fertilization treatments, and this ratio increased by 26.83% in fly ash treatment and 24.53% in bio-organic fertilizer treatment compared with CK2. 【Conclusions】 Fly ash and bio-organic fertilizer are satisfactory and more effective on amelioration of acid soil than other meterials tested.