| The tea-based land from conversion of cropland to forest is the second largest land use types, except the forest land in Three Gorges Reservoir Area. The management of tea garden has affected the quality of water, and now it is a common concern about how to cultivate and fertilize effectively, to ensure high production, and protect water from pollution resulted from soil erosion with nutrient loss. The research on soil nutrients' spatial variability of tea garden, is the premise for accurate management of regional crop productivity, a theoretical basis for effectively controlling the agricultural non-point source pollution, and a scientific basis for the establishment of soil nutrients'management systems, realization of scientific and rational fertilization and district management. For a long time, the studies on the spatial variability of nutrients about tea garden are few, and the researches in small-scale region with geo-statistics are nearly none. Therefore, this paper mainly studies on slope and spatial distribution of various nutrients in tea garden soil with the use of traditional statistical methods and geo-statistics in LanLing watershed, and the results are as follows:1) In horizontal and vertical directions of the slope, the soil nutrients changed as follows:Soil total P (TP):the distribution of nutrient content in the slope showed significant decreasing trend from slope top to bottom, that was the upper slope> middle slope> downhill slope. The vertical distribution of soil TP content in different slope positions were gradually decreased with soil depth. In the upper slope, the content was not significantly different, with the descending of slope, especially in middle slope and downhill slope, it had changed gradually. in each soil layer and had significant differences.Soil available P (AP):it was the same with TP in horizontal and vertical directions of the slope, and also showed decreasing trend from slope top to bottom, that was the upper slope> middle slope> downhill slope. In vertical direction, AP content showed decreasing tendency from surface soil layer to bottom in different slope positions, and changes in the middle slope were more significantly different than upper slope and downhill slope.Soil organic matter (OM):the slope distribution of soil nutrients in the top of the hill showed significant loss and its base enriched, and OM content had the opposite trend with P, that was downhill slope> middle slope> the upper slope. In vertical direction, OM content showed decreasing tendency in the different slope positions, The surface soil layer was higher than the bottom and changed gently with jagged distribution in different layers, and also in downhill slope,it was more significantly different than upper slope and middle slope.Soil total T (TN):the slope distribution of soil nutrients was uneven in the surface layer with little tendency, but in the bottom it showed significant loss in the top of the hill and its base enriched. In vertical direction, TN content also showed decreasing tendency in the different slope positions. TN content showed significant difference from slope top to bottom, and changed unevenly. In the entire slope, the vertical distribution of soil nutrients was anti "J" type.Soil ammonium nitrogen (NH4+-N):NH4+-N content also showed decreasing tendency from slope top to bottom. In vertical direction, the content in different slope positions was different, the distribution fluctuated significantly as zigzag type.Soil nitrate nitrogen (NO3--N):the distribution was uneven in horizontal direction and had no obvious trend, In vertical direction, it reached the maximum level at 2-3 soil layers, and with the jagged type.Soil pH:the horizontal distribution of soil pH changed evenly, there was no significant accumulation or loss from slope top to its base. In the vertical direction, it reached the lowest lever at 2 soil layer, the value increased gradually with the soil layer. It had the same trends in different slope, and the distributions were "J" type, but slightly different in the first layer, the rest showed a rising trend from the surface to the bottom. 2) The spatial variability of soil nutrients in the slope scale:The variation coefficients of soil total contents (TP, TN) and pH were small and showed a weak variation; and a strong variation with soil OM. The available nutrients (AP, NH4+-N) changed differently:AP showed strong variation; and NH4+-N showed middle variability in 0-5cm and 10-20cm, and a weak variation.in the rest.The best model to simulate the soil TP was spherical, and the effective ranges of different soil layers were 10-20cm (81.00m)> 40-60cm (71.00m)> 20-30cm (69.65m)> 30-40cm (64.36m)> 5-10cm (51.00m)= 0-5cm (51.00m). the values of Co/Co+C) in the surface layers (0-20cm) were between 0.25 and 0.75, that showed middle spatial correlation, while the bottom (20-60cm) was strong spatial correlation, that was to say, the spatial correlation in the surface was smaller than the bottom, and spatial correlation increased with the soil layers.The model of AP was the same as TP, and the effective ranges of different soil layers were40-60cm(29.41m)>30-40cm(25.02m)>20-30cm(24.97m)>0-5cm(23.38m)>10-20cm(21.0 0m)>5-10cm(20.97m), increased with the soil depth. In different layer, AP showed strong spatial correlation, except the layers in 5-10cm,10-20cm with value 0.038,0.058, the rest was smaller than 0.005.The first three layers of soil OM were mainly exponential model, the rest were better with spherical model, and the effective ranges of different soil layers were 0-5cm(213.00m)> 10-20cm(183.60m)>5-10cm(153.00m)>40-60cm(71.00m)=20-30cm(7 1.00m)>30-40cm(31.75m), with the surface larger than the bottom obviously. different layers were related to middle spatial correlation, and the spatial correlation, in the surface (0-10cm) was lower than the bottom.The first layer (0-5cm) of TN with exponential model, the second layer (5-10cm) with linear model, and the rest were spherical model, and the effective ranges of different soil layers were 10-20cm(26.01m),5-10cm(29.70m),30-40cm(64.94m) 20-30cm(65.24m),40-60cm(66.35m). The spatial correlation.in the surface layers of 0-5cm(0.498),10-20cm(0.400) were middle spatial correlation, in the layer of 5-10cm, it had no spatial correlation, and the rest were strong correlation.The content of NH4+-N from the soil surface to the bottom, appeared alternatively with exponential model and spherical model, and the effective ranges fluctuating largely, were 213.00m,81m,213m,71m,183m,61m and 81m. Spatial variability of different soil layers exhibited middle spatial correlation.The soil pH in the 5-10cm,10-20cm showed the exponential model, and the rest were spherical model, and the effective ranges were 81.00 m,243.00m,213.00m,71.00m, 77.10m,71.00m, Spatial variability of different soil layers exhibited middle spatial correlation. |
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