Fertilizer Use on Different Upland Cropping Systems for Soil Conservation in Yunnan
IPNI-1997-CHN-YN9
04 Feb 2008
2007 Annual Interpretive Summary
Sloping Land Management using Balanced Fertilization and Cash Crop Hedgerows in Yunnan, 2007
This is an on-going trial aimed at monitoring the effect of balanced fertilization (BF) in combination with contour cultivation and hedgerow crops as soil conservation measures against the traditional farmer practice (FP). From 2004 to 2006, this study was focused on monitoring soil conservation, soil properties, crop yields, and farmer income as affected by the combined influence of BF plus alley cropping using cash crop hedgerows. As the hedgerow crops grow bigger with time, their shading effects and proliferating root systems increasingly compete with in-field crops for light, moisture, and nutrients, especially for the woody species of hedge plants. In 2007, besides the above-mentioned routine measurements, the effects of different treatments on field slope changes were determined. The effect of soil erosion severity was assessed by simulation in a pot trial using corn.
The improved practices continued to maintain a higher corn yield than FP. Compared to FP, by introducing the Chinese priskly ash (FP+A) hedgerows, corn yield declined by about 1.3%, an indication that correct farming practices must be matched with correct nutrient management. The BF treatment produced the maximum corn yield among all treatments, 3.0% higher than the treatment of BF + hedgerows (BF+H). The yield reduction from the BF+H could be attributed to hedgerow occupation of land and its competition with corn for moisture and nutrients. Smaller corn plants seen near the hedgerows are evidence of this effect. When the income generated from the cash crop hedgerows is considered, the BF+H treatment turns out to be more beneficial than the BF treatment, a net income of US$218/ha higher than BF or US$991/ha higher than FP. The adverse effect of hedgerows on corn yield can be, at least partly, overcome by proper fertilization of the hedgerow crops.
Cash crop hedgerows have formed permanent ridges with deeply anchored roots and dense aboveground portions which effectively block soil from washing down from the upper plots to the lower plots. With time, these firm bunds now function as ‘natural’ terraces. This effect of terracing is more evident as the distance between the hedgerows across the slope is shortened. The farmers’ practice of planting down-the-slope greatly facilitates soil transport and loss. Soil productivity decreased proportionally with the amount of fertile topsoil contained within pots. The productivity, as indicated by both soil analysis and corn yield, is highly correlated to soil organic matter, both ammonium and nitrate-N, and available P and K. Amending the soil with proper amounts of manure and mineral fertilizers could partially offset yield losses, but not all, indicating the high value that should be placed on reducing the erosion of existing topsoils. Yunnan-09