| The Long Dong Loess Plateau is one of the most ecological fragile region in China. The severe soil erosion and declining of soil fertility are the main limiting factors of local agriculture and economy development. Developing pastoral agriculture systems have approved as one of the effective ways to solve the problems in the region. A series of field experiments were carried out in 2010 with the purpose of improving the land productivity, maintaining field water balance, and understanding dynamics of soil carbon pool. The experimental site was located in Quzi town, Huanxian county, Gansu province. The main results are as follows:1. Maize (Zea mays) has the highest dry matter yield among the 10 crops tested. Its yield reached 10.7 t/hm2 which was followed by sudan grass (Sorghum sudanense) 8.4t/hm2, lucerne (Medicago sativa) 7.6t/hm2, Hecao (a traditional way to produce forages by mixed sown of maize, millet and sorghum) 7.4t/hm2, proso (Echinochloa crusgalli) 7.2t/hm2, millet (Setaria italica)6.3t/hm2, oats(Avena sativa) 4.7t/hm2, sainfoin(Onobrychis viciaefolia) 3.9t/hm2, Hecao intercroping with vetch 2.9t/hm2 and soybean (Glycine max) 1.7t/hm2.2. Maize had the highest water use efficient (WUE), Its WUE was 34.05kg/hm2·mm, which was followed by Hecao 29.13kg/hm2·mm, sudan grass 23.28kg/hm2·mm, proso 20.50kg/hm2·mm, millet 19.99 kg/hm2·mm, lucerne 19.79kg/hm2·mm, oats 19.22kg/hm2·mm, Hecao intercroping with vetch 13.84kg/hm2·mm, sainfoin 9.87 kg/hm2·mm and soybean 5.72kg/hm2·mm.3. The precipitation during the growing season of the year can not meet the water requires of the crops, Water stored in the soil has to be consumed by the crops. Soil storage water in the depth of 0-60 cm showed regular seasonal variation and has strong relationship with the rainfall, however, the soil storage water in the depth of 60-200 cm was relatively stable during the crop growing season.4. The soil total carbon density of the top 60cm was ranged from 131.08 to 149.19 Mg/hm2 after crop harvested, which was no significantly difference compared with that in the same field at preplanting. There were, however, significant differences in soil total carbon density among the field growing various crops (P<0.05). The highest soil carbon density was detected in lucerne field at 0-30cm depth, which was followed by the fields growing sudan grass, whereas the lowest soil carbon density was found in the field of Hecao. Compared with preplanting, the light fraction carbon content in the top 20 cm soils of field growing lucerne, maize, sudan grass, proso and soybean, respectively, were significantly increased by the crops (P<0.05), however, there were no significant differences in the soils between preplanting and after harvesting in the 20-60cm soil layer (P>0.05). In the 0-60cm soil layer, particulate organic matter carbon content and mineral-associated carbon content of all forage crops were not differed significantly between preplanting and after harvesting (P>0.05)... |
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