Effects of lime and chicken manure on nutrient cycling, soil properties and plant response in acid South African ultisols.

摘要

The soil incubation and greenhouse studies described herein were conducted to determine the: (1) effects of lime, broiler chicken manure and their interaction on soil chemical properties, microbial activity, N mineralization, N uptake and maize growth; (2) residual effects of liming and interactions between urea fertilizer and chicken manure on maize growth, N uptake, and N recovery, using two acid South African Ultisols. The overall treatment effects varied between the two soils. In the low acid saturated (Nikwe) soil, total CO2 evolution and N mineralization increased as the rate of chicken manure application increased. However, liming and the accompanying increase in soil pH had no apparent effect on CO2 evolution and N mineralization. In the high acid saturated (Magusheni) soil, total CO2 evolution was lower in unlimed than in limed treatments. However, in limed treatments, the increased microbial activities were accompanied by immobilization of N. These findings agreed with the greenhouse study reported in chapter 2, where chicken manure increased but liming had no apparent effect on N mineralization, total N uptake, and plant biomass production in the Nikwe soil. Similarly, in Magusheni soil, when both lime and chicken manure were applied, immobilization of N occurred and that reduced total N uptake and delay maize growth and development. However, under field conditions the long-term effect of liming in the Magusheni soil is expected to be a net increase in N availability. Results for Chapter 3 showed that liming enhanced plant growth responses to N fertilizer in the Magusheni soil. In the Nikwe soil, N fertilizer increased plant growth responses, however, the responses tended to be similar or lower in limed than in the unlimed soils. Therefore, liming was essential to correct the acidity in the Magusheni soil, whereas in the Nikwe soil, liming was not a necessity. The lack of a liming effect in the Nikwe soil is attributed to the relatively high initial soil base status and the lower levels of acidity. The stimulating effect of lime in the Magusheni soil is attributed to the relatively low initial soil base status and the higher levels of acidity.