Subjects: Biology >> Ecology submitted time 2017-11-29 Cooperative journals: 《中国生态农业学报》
Abstract： Soil carbon sequestration is an important way to reduce greenhouse gas emissions. Milk vetch and other green manures importantly impact annual variations of CO2 concentration in the atmosphere by promoting soil organic carbon accumulation and improving cropland soil fertility. However, research on the optimal arrangement of milk vetch plantation had to-date been hardly integrated with the suitability croplands for milk vetch plantation and realistic need for soil carbon sequestration. This study aimed to arrange milk vetch in the most suitable areas and fix as much CO2 as possible. Thus the suitability of milk vetch plantations in croplands was evaluated by analyzing soil organic carbon density (SOCD) in croplands based on the 1:50 000 scale database of land use / soil pattern in Pucheng County, Fujian Province. The optimal arrangement of milk vetch plantations in Pucheng was done using an integrative method in GIS environment. Then the modificatory weighted index sum method and dynamic clustering analysis were used for both land suitability and SOCD by dividing the index based on the principle of land suitability for milk vetch plantation and carbon sequestration needs of croplands. The priority, sub-priority and general plantation areas of milk vetch in Pucheng were optimally arranged based on the principles of preferential arrangement of croplands with low topsoil SOCD and high suitability for milk vetch growth. The results showed that 81.82% of the croplands in the study area had various suitability of milk vetch plantation. The annual total yield of fresh milk vetch, annual carbon sequestration and cultivated land area of milk vetch were respectively 657 056.65 t, 29 900.74 t and 23 677.72 hm2. If milk vetch was planted in all the cultivated lands in the study area, the application rate of green manure was 27.75 t×hm-2 per year. The range of SOCD in the study area was 2.50–5.74 kg×m-2, differing sharply in space. On the basis of total cropland in Pucheng County, optimal area arrangement for milk vetch plantation was 59.72%, of which priority and sub-priority regions dominantly accounted for 25.72% and 50.34%, respectively. Priority region was mainly distributed in the basin area, sub-priority region distributed in the 200-400 m altitude range with gentle slope terraces, while general region was located in 250-800 m altitude range on slope terraces. The towns (including Liantang, Shuibei, Gulou, Yongxing and Zhongxin), which most needed soil carbon sequestration, were planned as key developing areas. Then towns (e.g., Fuling, Xianyang, Shipi and Jiumu) were planned as reserve areas for milk vetch plantation. The study provided the needed guide for the efficient planting and utilization of milk vetch. This showed the need to increase scientific implementation of soil organic matter programs and the continuous improvement of farmland quality by preferentially selecting suitable areas for milk vetch planting based on land suitability and carbon sequestration needs of croplands.
Subjects: Biology >> Ecology submitted time 2017-11-29 Cooperative journals: 《中国生态农业学报》
Abstract： Phosphorus is one of the largest nutrient elements needed by plants. Under the intensive production conditions, most of farmland soils in China have emerged the phenomenon of phosphorus enrichment. This is mainly due to excessive application of phosphate fertilizers, the strong fixation and inefficient use of phosphorus. The enrichment of phosphorus in cropland soils is one of the important reasons caused nonpoint pollution and has also restricting the sustainable development of agriculture in China. In this study, based on a 1∶250 000 spatial database of farmland soil types and the available phosphorus data of cultivated soil samples (1 676 samples in 1982 and 200 322 samples in 2008) in Fujian Province, the spatial difference of phosphorus enrichment degree and its influencing factors in cultivated land during the past 26 years were studied and discussed by GIS technology integrated with grey correlation analysis model. The aim of the study was to uncover the enrichment characteristics of soil available phosphorus, spatial variability and its influencing factors, so as to improve the efficiency of phosphorus use and reduce the application of phosphate fertilizer in cultivated land soils. The results showed that the soil available phosphorus was abundant in Fujian Province during the past 26 years. In addition, the soil available phosphorus enrichment area reached 1 216 777 hm2, accounting for 92.81% of the total area of cultivated land in the province, whereas the yearly average enrichment amounts and rates of available phosphorus were 24.38 mg×kg-1 and 10.01%, respectively, which showed obvious spatial difference. The cropland soils in Xiamen, located in the southern subtropics, showed the largest degree of effective phosphorus enrichment, while those in Nanping located in the mid-subtropics showed the lowest degree of effective phosphorus enrichment in Fujian Province. The soil types with high effective phosphorus enrichment included Purplish soils, Fluvo-aquic soils, Paddy soils and Latosolic red soils and those with less effective phosphorus enrichment included Coastal Solonchaks and Calcareous soils. Soil subtypes with larger degrees of available phosphorus enrichment included Submergenic paddy soils and Bleached paddy soils, and those with lower levels of available phosphorus enrichment included Brown calcareous soil and Coastal Solonchaks. In general, the available phosphorus in the soil layer has the characteristics of large enrichment area, wide distribution range and significant spatial difference. The results by grey correlation model analysis showed that the soil available phosphorus enrichment and its spatial difference were mainly affected by annual application rate of annual phosphate fertilizer, pH, annual mean temperature and clay content, the grey correlation coefficients of these influencing factors were higher than 0.722. However, the effect of sand, annual precipitation and organic matter on the phosphorus enrichment of cultivated soil in the study area was relatively weaker. The gray correlation coefficients of these influencing factors were lower than 0.720. Based on the degree of phosphorus enrichment and spatial difference, inorganic phosphate fertilizer management measures and strictly control the use of it can play a key role in dealing with the effective phosphorus enrichment of cultivated soil in Fujian Province. At the same time, it was also essential to optimize the fertilization management plan by increasing organic fertilizer and reducing chemical fertilizer.
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