Soil health and nutrient Budgeting as influenced by different cropping sequences in an Vertisol of Tamil Nadu

Abstract

To study nutrient status and nutrient balances, soil carbon pools, physico chemical characteristics as influenced by different cropping sequences, soil samples were analysed in the three year old experiment during 2014-15 in the Eastern block area of TNAU, Tamil nadu. The different cropping sequence includes, viz., CS I-maize-cowpea (G)-radish (0.20 ha), CSII -bhendi-maize + cowpea-sunflower (0.20 ha), CS III: chillies-maize- sunhemp (0.20 ha), CS IV : cowpea (v)-cotton-sunflower (0.20 ha). The soil sample results on carbon pool shows that, high value of water soluble carbon was observed with CS IV(147 mg/kg). Walkley and Black method of estimating carbon (WBC) is equivalent to Total organic carbon (TOC). More TOC was measured in CSII (7895 mg/kg) i.e. Bhendi-Maize+cowpea-sunflower cropping sequence. CSIV registered high active carbon of 656 mg/kg. The higher value of passive carbon was recorded in CSII: bhendi-maize+cowpes-sunflower. Higher available N content was recorded CS I (263 kg/ha). Higher available P content of 21.2 kg/ha recorded in the CSII and available K in CS III (795 kg/ha) was recorded. Soil biological parameters like bacteria, fungi, actinomycetes population and dehydrogenase activity were better expressed in CS II (62 cfu x 10-6 g/soil, 29 cfu x 10-4 g/soil and 15 cfu x 10-3 g/soil) and 118.5 mg TPF/kg/24 hrs respectively than the other cropping sequences. The higher maximum water holding capacity of 51.4% and porosity (48.3%) was recorded in the CSII. Regarding the nutrient removal, CS IV recorded higher N uptake of 109.2 kg and higher P uptake of 31.7 kg and CSIII recorded higher K uptake (82.5 kg).But in the case of nutrient balance studies, between expected and actual N status is positive in CS II. In the P nutrient balance, expected and actual P status difference is negative in all the cropping pattern i.e the applied P excess is fixed in the soil. The balance between expected and actual K status is positive in all the cropping system.