The Fertility Of New Terrace And Its Soil And Water Conservation Ability In Northern Qinling Mountain

The serious soil erosion has depressed the agricultural production development ofmountainous area heavily, and become an important factor destroying the ecologicalenvironment of mountainous area. While changing the slope land to terrace (theslope-to-terrace, or new terrace) is an important engineering measure to control soil and waterand nutrient losses. In order to make the terrace play a key role to increase crop yield as soonas possible, we need to understand the soil nutrient status of the new terrace, and then use afertilization measures. At present, most of the researches are concentrated in the loesshilly-gully region and southern hilly region in China. And there are a few studies in NorthernQinling Mountainous area in Shaanxi. Therefore, we have studied the soil nutrient status, theeffect of different fertilization measures and characteristics of soil and nutrient losses of thefarmland in the Yujia river catchment of Zhouzhi country in Northern Qinling Mountain.We have determined the status of soil fertility of the new terrace in the study region. Andthe fertilizer experiments were conducted in the slope farmland and newly-built terracerespectively. We studied the effect of the slope-to-terrace measures on preventing andcontroing soil and water loss of the slope farmland in Northern Qinling Mountain. Our mainconclusions are:1. We have determined the soil nutrients content of the newly-built terraces in Yujia rivercatchment, then evaluated soil fertility with the classification standard of Shaanxi soil nutrientcontents. The results showed that the soil average pH of the newly-built terraces are7.88, it isweakly alkaline. The average content of SOM was1.73g·kg-1; for soil total N, it was0.69g·kg-1; and both were in the low and very low levels. The soil mineral N、available P andavailable K average contents were6.02、5.95and116.1mg·kg-1respectively.The content ofsoil mineral N was extremely low; and available P contents was mostly in low and very lowlevels; and available K contents was mainly in medium level. The soil nutrient contents intopsoil of the slope farmland were higher than the newly-built terraces. The soil nutrients in3yeared terrace are higher than that in1yeared terrace. As the increasing years of cultivation,the contents of SOM, total N and available K in soils of the newly-built terraces increasedsignificantly. Overall, compared to slope farmland, the newly-built terraces were in lack of nutrients at their young age, but along with the increasing years of cultivation, the soilnutrient conditions are gradually improved. We suggest that more attention should be paid tothe application of manures and nitrogen and phosphorus fertilizers to improve soil fertilityand crop production.2. Field fertilizer experiments were conducted in the slope farmland and the newly-builtterrace to compare the effects of different fertilizer treatments on crop yields and nutrientuptakes. The result showed that both NPM(K)(applied manure plus inorganic NPK fertilizers)and N控NP(K)(controlled release urea coupled with common urea) improved the crop yieldswhen the nitrogen has a20%reduction. NPM(K) had the best effect in the newly-builtterrace, the yield of wheat and corn were increased by13.1%and8.2%respectively; while N控NP(K) had the best effect in the slope farmland, the yield of wheat and corn were increasedby21.7%and11.0%respectively. On the slope farmland, N控NP(K) promoted the absorptionof N, P, K significantly; on the newly-built terrace, the nutrients uptake under the NPM(K)were higher than that under the N控NP(K) significantly. NPM (K) treatment in both the slopefarmland and the newly-built terrace increased the available nutrient contents in the arablelayer significantly after crop harvested, has played a good role on improving soil fertility. Inaddition, the crops yield, nutrients uptake and available nutrient contents of the arable layer inthe slope farmland were higher than that in the newly-built terrace. Therefore, in order to givea full play on the potential to increase production of the newly-built terrace, we need tocontinue to strengthen on improving the soil fertility.3. A field observation experiment of runoff plots was conducted to study the effect of soiland water and nutrients conservation ability of the slope-to-terrace measure, and the influenceof different measures on soil and water and nutrient losses in slope farmland and newly-builtterrace. The results showed that, compared to the slope farmland, the amount of runoff andsediment of the newly-built terrace after rainfall decreased by68.8%and91.2%, respectively;the total nitrogen (TN), total phosphorus (TP) and mineral nitrogen in the runoff decreased by29.8%,72.3%and26.3%respectively. In the terrace, the runoff and sediment yield wereshown as NPK (conventional fertilization+slope planting)> NPKM (straw mulching+contour planting)> N控NPK (controlled release urea coupled with common urea+contourplanting); the runoff were hold by57.3%,81.9%respectively under the NPKM and N控NPKtreatments, and the sediment were hold by20.9%and78.1%respectively, and the twotreatments all decreased the amount of mineral nitrogen, TN and TP in the runoff in differentdegrees, especially in the best of N控NPK. The loss forms of nitrogen and phosphorus in therunoff mainly were dissolvable nitrogen and particulate phosphorus; the runoff and sedimentyield and the amount of the nitrogen and phosphorus in the runoff under the heavy rainfall (22.4mm·h-1, rainstorm) all higher than that under the light rainfall (3.2mm·h-1, moderaterain), they increased by32.2%,96.6%,66.3%and81.1%respectively. On the whole, theterrace benefit for the soil and water and nutrient conservation; recommended fertilization andcontour planting has a good effect on controlling water and soil and nutrient losses.