| The problem of desertification had been attracted international community's high attention. Biological and engineered measures were considered to be effective ways to resort it. Lespedeza bicolor Turcz,which was considered to be one of the best native species in Zhanggutai areas, has the characteristics of cold resistance and drought resistance. The well developed taproots and root nodules on laterals can fix and improve sandy-soil. Lespedeza bicolor Turcz is excellent biologocal material species in Horqin and even other sandland. In semi-arid areas, plant growth is constrained by water and nutrients. So promoting plant growth by adding water and fertilizer has became one of major measures. With 312-D optimized saturation design, water and fertilizer coupling experiments were conducted on Lespedeza bicolor Turcz in semi-arid area in northwestern of Liaoning province Zhang-gu-tai area. Nine indexes were measured in the experiment:height, radical diameter, biomass, chlorophyllcontent, water potential, proline, peroxidase, malondialdehyde and superoxide. Regressive mathematical models were set up respectively to find out quantitative relationship and mechanism of water and fertilizer coupling. The aim of the experiment was to improve the use efficiency of water and fertilizer in semi-arid sandland and to provide theoretical foundation for optimizing the management of water and fertilizer in the production of Lespedeza bicolor Turcz. The results were as follows:The mathematical model of height with water(X1), nitrogen(X2) and pho sphorus(X3):Y=67.799+4.082 X1+0.864X2+0.401 X12-0.750X22-3.360 X32-0.44 6X1X2-0.665X1X3+1.098X2X3. Too much nitrogen and phosphorus had inhib ited height growth, but water had promoted height growth. The most suitable conditions for height were water content of soil 17.52%, nitrogen 266.822 kg. hm-2-455.140 kg.hm-2 and phosphorus 380.374 kg.hm-2.The mathematical mode 1 of radical diameterand with water(X1),nitrogen(X2) and phosphorus(X3):Y= 7.865+0.365X1+0.332X2+0.263 X3-0.186X12-0.346X22+0.319X1X2+0.208 X2X3.With the increase of water and nitrogen, radical diameter had increased and then decreased, with the increase of phosphorus decreased and then incr eased. The most suitable condition for radical diameter were water content of soil 15.98%～17.52%, nitrogen 455.140 kg.hm-2 and phosphorus 760.748 kg.h m-2. The mathematical model of biomass with water(X1), nitrogen(X2) and p hos-phorus(X3):Y=15.498+5.047 X,+3.906 X2+0.571 X,2-1.164X22-1.489 X32+0.444X1X2-0.890 X1X3+0.545X2X3. As nitrogen and phosphorus incr eased, biomass increased first and then decreased, as the moisture increased, b iomass increased. The most suitable condition for biomass was about:water c ontent of soil 17.52%, nitrogen 78.505 kg.hm-2～455.140 kg.hm-2 and phosphor us 190.187 kg.hm-2～380.374 kg.hm-2.The mathematical model of chlorophyll content with water(X,), nitrogen (X2) and phosphorus(X3):Y=40.495+1.398X1+0.791 X2+0.569X3-0.605X22+ 0.452X2X3.With the nitrogen and phosphorus increasment, chlorophyll content had increased first and then decreased, with water increasement. chlorophyll content increased. The most suitable condition for chlorophyll content were w ater content of soil 17.52%, nitrogen 455.140 kg.hm-2 and phosphorus 760.748 kg.hm"2. The mathematical model of water potential with water(X1), nitrogen (X2) and phosphorus(X3):Y=-2.877+0.250X1+0.086X3-0.028 X12+1.128X32-0. 038X1X2+0.033X1X3-0.058 X2X3. Leaf water potential had increased with th e water, with phosphorus increased first and then decreases. The most suitable conditions for water potential were water content of soil 17.52%, nitrogen 0 kg.hm-2 and phosphorus 570.561 kg.hm-2. The mathematical model of proline and water(X1), nitrogen(X2) and phosphorus(X3):Y=2.667-1.507X1+0.139 X2-0.877X3+0.461 X12+0.851 X22+0.888X32-0.129X1X2+0.634 X1X3. With w ater, nitrogen and phosphorus increasement, proline increased first and then de creased. The most suitable condition for proline were water content of soil 17. 52%, nitrogen 266.822 kg.hm-2 and phosphorus 190.187 kg.hm-2-380.374 kg.h m-2). The mathematical model of peroxidase with water(X1), nitrogen(X2) a nd phosphorus(X3):Y=24.690+8.998X1+2.136X2+6.506X12-1.455X22+1.494 X1X2-5.165X1X3+2.176X2X3. With the water incresement, peroxidase had de creased first and then increased. With the increase of nitrogen, peroxidase incr eased first and then decreased. The most suitable condition for peroxidase w ere water content of soil 17.52%, nitrogen 533.178 kg.hm-2. The mathematical model of malondialdehyde with water(X1), nitrogen(X2) and phosphorus(X3): Y=10.591+0.305 X1-1.805 X3+1.127 X12+0.892 X22+1.650X32+0.792X1X3-0.54 5X2X3. As water, nitrogen and phosphorus increased, malondialdehyde decre ased and then increased. The most suitable condition for malondialdehyde w as about:water content of soil 8.55%-12.26%, nitrogen 266.825 kg.hm-2, phos phorus 570.561 kg.hm-2. The mathematical model of superoxide with water (X1), nitrogen(X2), phosphorus(X3):Y=61.798+5.819AX1+1.455X3-2.749X12-5. 089X22-9.352X32+4.132X1X2+1.696X2X3. As water, nitrogen and phosphoru shad increased, superoxide increased first and then decreased. The most suitab le condition for superoxide were water content of soil 15.98%, nitrogen 266.8 22 kg.hm-2 and phosphorus 380.374 kg.hm-2. |
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