The Research On Nutrient Balance Of Orchard Soil In Karst Areas

Karst ecosystems are inherently vulnerable and are characterized by a two-layer structure. Degradation may occur through both natural and anthropogenic processes, which can become so extreme that with some justification one may refer to the creation of a "rocky desert", even in south China that have high levels of rainfall. As well, these areas are the home of over 100 million people, of which approximately 35% represent more than ten minorities who have been relying on traditional agriculture as their main source of income. Farmers manage the land according to their experiences, producing goods mainly for home and local consumption and clearing forests for fuel.In this paper, orchard agro-system was introduced, and surverys in February, June and September, were completed to ananlyze the soil fertility in karst orchard areas. The correlation between total N,P,K and available N,P,K is examined to compare soil fertility in different soil type, thereafter to estimate the orchard soil fertile level, and to valuate the balance statue of nutrients during growing season. The result of the study showed:(1) Although the tatol nitrogen is rich in calcareous soil, yet the available nitrogen is relatively poor according to standard of National Second Soil Survey. Phosphorus is variate according to field samples, with, generally, rich in total phosphorus, however the available phosphorus tend to be depletion, in generally, the content of top soil (0-10cm) is rich, but the middle profile(10-20cm) and the under profile(20-30cm) are farely depletion, the under profile of some orchard soil , contain just trace available phosphorus. The total and available potassium is strongly depletion, with former one being crueler. Most sample for the available potassium is a mid depletion. Meanwhile, in red soil, the nitrogen is not rich with a limited and mid depletion, all samples in June were showed the soil nitrogen is a mid depletion. Both the total and available phosphorus wee strongly depletion red soil, and total potassium fertility, which available potassium is better with middle depletion. The result suggested that in the orchards of calcareous soil, less nitrogenous fertilizer is needed comparing to phosphatic and potassium; phosphatic manure and potassium fertilizer in calcareous soil are appeal to apply. While that in red soil, because the available nitrogen is not very poor, but the total nitrogen is depletion, it is recommended that the nitrogenous, phosphatic manure and potassium fertilizer should be applied.(2) ANOVA is used in data statistic. It shew that correlation between total and available nitrogen are significant P=0.000. The total nitrogen might be basic nitrogen pool for the available nitrogen. As well, the correlation between total and available phosphorus in all orchards are significant with p= 0.018. The result indicated that a balance fitilising is neccesarry for total and available phosphorus when phosphatic manure is applied. Howver, the correlation between total...