Effects Of Fertilization On Growth And Ecological Characteristics Of Pasturs On Abandoned Cultivated Land In Farming Pasture Region

In order to provide scientific basis for improving the use of abandoned cultivated land, and protect ecological environment of deste steppe of Ningxia,6pastures type(Medicago sativa L., Melilotus suaveolens Ledeb., Astragalus adsurgens Pall., Agropyron cristatum(L.) Gaertn., Agropyron mongolicum Keng. and Elymus dahuricus Turcz.) were selected and planted on abandoned cultivated land by using orthogonal experimental design of L18(61×36) to compare the effects of organic manure, chemical fertilizers and straw of Sophora alopecuroides on growth and ecological characteristics. The main results showed as following:1. The average fresh yield and dry yield of legumes were22106.15kg/hm2and8559.97kg/hm2respectively, which significantly (P<0.05) higher than gramineae. The average fresh yield of M.sativa was23395.35kg/hm2, which significantly (P<0.05) higher than M.suaveolens and A.adsurgens. When application amount of organic manure reached36t/hm2, the average fresh yield and dry yield were22106.15kg/hm2and8559.97kg/hm2respectively, which significantly (P<0.05) higher than the treatment of12t/hm2or24t/hm2. The average fresh yield and dry yield under the treatment of moderate levels of NPK (N15kg/hm2+P135kg/hm2+K135kg/hm2) were16295.73kg/hm2and6054.66kg/hm2respectively, which significantly (P<0.05) higher than the treatment of low levels of NPK (N55kg/hm2+P45kg/hm2+K45kg/hm2). When straw returning10t/hm2to the field, the average fresh yield and dry yield of pastures were16388.67kg/hm2and6054.57kg/hm2respectively, which significantly (P<0.05) higher than the treatment of5t/hm2or15t/hm2. Therefore, the optimum combination was organic manure36t/hm2+moderate levels of NPK+straw of Sophora alopecuroides10t/hm2, which can be better increase pasture yield. In the experiment the dry yield (10353.60kg/hm2) of M.suaveolens was the highest under the optimum fertilization combination, and the fresh yield (25444.52kg/hm2) of M.sativa was the highest under the similar optimum fertilization combination.2. The average net photosynthetic rate (Pn) of legume was20.19μmol/m2·s, which significantly (P<0.05) higher than gramineae. M.suaveolens had the better photosynthetic capacities, its average Pn was23.92μmol/m2·s, which significantly (P<0.05) higher than M.sativa and A.adsurgens. When application amount of organic manure reached36t/hm2, the average Pn was16.52μmol/m2·s, which significantly (P<0.05) higher than the treatment of12t/hm2or24t/hm2. The average Pn under the treatment of moderate levels of NPK (N165kg/hm2+P135kg/hm2+K135kg/hm2) was15.98μmol/m2·s, which significantly (P<0.05) higher than the treatment of low and high (N275kg/hm2+P225kg/hm2+K225kg/hm2) levels of NPK. The average Pn under the treatment of straw returning10t/hm2to the field was15.52μmol/m2·s, which significantly higher than the treatment of15t/hm2. The optimum combination was organic manure36t/hm2+moderate levels of NPK+straw of Sophora alopecuroides10t/hm2, which can be better promote photosynthetic capacities.3. Legume had the better quality, its average crude protein content was18.58%, which significantly (P<0.05) higher than gramineae. M.sativa had the bast quality, its average crude protein content was 20.61%, which significantly (P<0.05) higher than M.suaveolens and A.adsurgens, its average crude fiber content was23.59%, which significantly (P<0.05) lower than M.suaveolens. Gramineae in E.cylindricus had the better quality, its average crude protein content was14.29%, which significantly (P<0.05) higher than A.cristatum and A.mongolicum. When application amount of organic manure reached36t/hm, the average crude protein content was15.82%, which significantly higher than the treatment of12t/hm or24t/hm. The average crude protein content under the treatment of moderate levels of NPK was15.50%, which significantly (P<0.05) higher than the treatment of low levels of NPK. Therefore, the optimum combination was organic manure36t/hm2+moderate levels of NPK+straw of Sophora alopecuroides5t/hm, which can be better increase pasture quality.4. The average moisture of gramineous grass was6.50%and higher than Legume grass. The soil organic matter of legume grassland was10.02g/kg and significantly higher than that of gramineous grass. When application amount of organic manure reached36t/hm, the average moisture was6.41%and significantly (P<0.05) higher than the treatment of12t/hm2, the soil organic matter was10.02g/kg and significantly (P<0.05) higher than the treatment of12t/hm2and24t/hm2. The average moisture under the treatment of moderate levels of NPK was6.37%, which significantly (P<0.05) higher than the treatment of low levels of NPK. The average moisture under the treatment of straw returning10t/hm2was6.39%. The soil organic matter under the treatment of straw returning15t/hm2was9.83g/kg and which significantly (P<0.05) higher than the treatment of5t/hm and10t/hm. Therefore, the optimum fertilization combination to improve soil moisture was organic manure36t/hm2+moderate levels of NPK+straw of Sophora alopecuroides10t/hm, the optimum combination to increase soil organic matter content was organic manure36t/hm2+moderate levels of NPK+straw of Sophora alopecuroides I5t/hm2.