西藏中部退化土壤在不同培肥措施下的肥力特征

Effects of different fertilizing manners on the fertility characteristics of the degraded soil in central Tibet

于西藏中部春播条件下就不同培肥方式对退化土壤物理、化学和生物性质的影响以及土壤肥力因子间的相互关系进行了研究。结果表明 ,化肥、有机肥 ,特别是有机 -无机肥配合施用在协调土壤环境 ,促进以细菌为主导的土壤微生物繁殖以及土壤有机质、土壤团粒结构形成和土壤养分转化等方面具有重要作用 ;退化土壤物理、化学和生物性质呈现出变化特征的相对一致性 ,并在总体上呈现出较为明显的恢复态势 ,突出地反映了高原高寒以及干旱、半干旱条件下退化土壤所具有的在相对较短的时间内实现肥力恢复及结构重建的可能性及其潜力。石灰性土壤条件下 ,耕层土壤有机质以及不同土层全氮、有效氮、全磷、有效磷的绝对增长量较大。同时 ,不同培肥方式对不同土层土壤真菌、固氮菌以及耕层土壤放线菌的繁殖普遍具有不同程度的抑制作用 ;不同土层土壤固氮菌与纤维素分解菌均呈负相关。

A spring-wheat field trial (2001～2002)was carried out to investigate the effects of different organic or inorganic fertilizer applying manner on the physical, chemical or biological characteristics of the degraded soil and the interactions among the soil fertility factors in central Tibet. A 4×4 split-plot design was employed. Organic fertilizer (sheep manure containing 7 g/kg N, 4.9 g/kg P_2O_5, 2.8 g/kg K_2O and 267g/kg O.M respectively) was the main treatment which included four (0、7.50、26.25、45.00 t/(hm^2·a) levels. At each main treatment, four subtreatments, N_0P_0K_0(0-0-0 kg/(hm^2·a) as N-P_2O_5-K_2O), N_1P_1K_1(60-24-12 kg/(hm^2·a), N_2P_2K_2(120-48-18 kg/(hm^2·a) and N_3P_3K_3(180-72-24 kg/(hm^2·a), were set using urea, calcium superphosphate and potassium sulphate as fertilizers. The results were shown that the applying of inorganic or organic fertilizers enhanced the formation of soil aggregates, particularly, the larger aggregates, while bulk density and porosity of soil were not affected. Comparing with non-fertilized treatment soil organic matter was increased by fertilization by 85.6% in plough layer, but decreased by 10% in 31~60 cm layer. In calcareous soil, all fertilization treatments had higher available P but lower total N and available K in the soil of plough layer, the available P level was as high as 21.74 mg/kg in average while the total N and available K were only 0.177 g/kg and 45.57 mg/kg respectively. The organic matter content in plough layer or the content of total N, available N, total P, available P in different depth of soil profile showed higher net increasing by fertilizations. Propagation of fungi and N fixing bacteria in the layers of 2~30, 31~60 cm and of actinomyces in 2~30 layer cm soil layer were suppressed by fertilization. Bacteria was dominant group in biome of the soil microbe community in all layers of the soil profile. Nitrogen-fixing bacteria reduced by the increase of the cellulose-decomposing bacterium in different horizon. Fertilization increased the proportion of bacteria in soil, the increment in deep layer was higher than that in plough layer. Applying of inorganic fertilizer increased the organic matter by 62.0%, soil total N by 300.0%, total P by 74.0%, available N by 73.5% and available P by 217.0% respectively; soil bacteria amount was increased by 57.5% in average. The effects of fertilization on crop yield showed similar trend as on soil fertility. It is concluded that the recovering of soil fertility would take long term without fertilization in central Tibet. All different fertilizing manners had significant and prompt effectiveness on the coordinating of soil environment, on promoting the process of bacteria-dominating propagation of soil microorganism, on enhancing the accumulation of soil organic matter and the reconstruction of soil structure, and on increasing the pool of N and P comparing with non-fertilization. The changing of physical, chemical or biological characteristics of the degraded soil showed similar ways among the different fertilizations. Soil fertility showed a significant recovering trend after applying of fertilizers, which demonstrated the possibility and potential of recovery of soil fertility and reconstructing of soil structure in relative short period.