Recovery of organic fertility in degraded soil through fertilization and crop rotation

Maintenance and enhancement of the quality of degraded soil are, in essence, dependent upon the improvement of physical, chemical and biological properties of the soil. Improvement in microbial parameters of the degraded soil was studied in the present experiment through the effect of fertilizer sources and levels and cropping patterns in a factorial design in northern Pakistan. The experiment was designed in RCB with split plot arrangements. Cropping patterns i.e. maize–wheat–maize (C1), maize–lentil–maize (C2) and maize–wheat + lentil intercrop-maize (C3) were kept in main plots while fertilizer treatments; the control (T1), 50% NP (T2), 100% NPK or the recommended dose (T3) and 20 t ha−1 farmyard manure integrated with 50% mineral N and 100% P and K (T4) were tested in sub-plots during the study. Maximum and significant improvement in microbial parameters was recorded in T4 with 44, 24, 27 and 24.6% increase in total nitrogen (total N), mineralizable nitrogen (MN), microbial biomass nitrogen (MBN), and microbial biomass carbon (MBC) after a 10 day incubation period over the T3, respectively, in the surface soil and 10%, 21%, 24% and 24.2% increase in the corresponding microbial parameters in the sub soil. The cropping patterns having cereal–legume rotation also improved organic soil fertility by 25%, 11.4%, 13% and 44% increase in total N, MN, MBN and MBC after a 10 day incubation period over the cereal-cereal rotation, respectively, in surface and 4%, 11%, 10% and 31% increase in the corresponding microbial parameters in the sub surface soil. The conclusion was that degraded alfisols require 50% N from the organic sources out of its total N requirements along with the inclusion of legumes in the traditional cereal–cereal crop rotation for the recovery of its microbial parameters.