Characteristics of soil nutrient contents of five different cultivated lands in Longzi County, Tibet

Five different types of cultivated lands, which were mainly planted for barley (Avena nuda), potato (Solanum tuberosum), alfalfa (Medicago sativa), sickle alfalfa (Medicago falcata) and rape (Brassica campestris) mixed with pea (Pisum sativum), respectively, were selected in Longzi County, Tibet and the nitrogen status of various forms, phosphorus content, soil organic matter (SOM) content and soil pH were analyzed in the present study. The results showed that the average soil nutrient contents in different types of cultivated lands were different and SOM and total N contents in potato land were significantly higher (P<0.05) than the other four cultivated lands. In general, the average contents of SOM and total N for all five cultivated lands were 2.59% and 0.18%, respectively, which indicated that the soil fertility was high in all cultivated lands. There was little variations for ammonium contents in different cultivated lands, however, there was strong variations for nitrate contents in different cultivated lands with the highest nitrate content in sickle alfalfa farmland. The C/N ratio of SOM was low which attributed to accelerate the mineralization of soil organic nitrogen. Phosphorus content was rich in all the five types of cultivated lands with the average content of 0.13% although it was a little bit lower in the two types alfalfa lands. The mean pH of all the lands changed from 8.12 to 8.48, which suggested that it was all alkalescence in Longzi. Different crops had different effects on soil pH and barley land had significantly higher pH than that of other lands. There were complicated correlations between soil nutrient properties in the soils of cultivated lands. Both SOM and total N had very positively significantly correlation (P<0.01) with total P, ammonium and nitrate N. There was no correlations between each other of total N, ammonium and nitrate N. Soil pH had very negatively significantly correlation (P<0.01) with nitrate N.