Carbon sequestration and nutrient dynamics in a long-term lantana amended soil under rice wheat system

Abstract

A long-term field experiment was started during Kharif 1988 with four levels of lantana addition (0, 10, 20 and 30 t ha-1) on fresh weight basis and three fertilizer levels (33, 66 and 100 per cent of recommended N and K to rice and 66 per cent of N, P and K to wheat). The application of P to rice was totally omitted. Chopped lantana was added 10 to 15 days before transplanting of rice every year. The experiment was conducted in randomized block design with twelve treatments replicated three times. The present study Carbon sequestration and nutrient dynamics in a long-term lantana amended soil under rice-wheat system , was undertaken from Kharif 2004 to Rabi 2005-06. The soils of the experimental site were acidic and classified taxonomically as Typic Hapuldalf . Soil samples from 0-0.15 and 0.15-0.30 m soil depths were taken after the harvest of Rabi wheat 2004-05 and were analyzed for different active, slow and passive pools of SOM, active and passive pools of N, P and S besides this, different physical, chemical and biological properties of the soils. Out of the total organic matter added through lantana addition from 10 to 30 t ha-1 over the last 17 years, the average sequestration in the soil was only about 19 per cent out of which about 60 per cent was retained in passive pools and only 11 per cent in active pools. Continuous lantana addition and fertilizer application has also increased total C stock, C stock ha-1 yr-1 and retention of all active and passive pools of C in the soil. With increasing/improvement in all the pools of N, P and S as well as physical, chemical and biological properties of soil with increasing levels of lantana addition and fertilizer application, the maximum rice and wheat yield as well as uptake of N, P and S was obtained under 20 t ha-1 lantana addition alongwith 66 per cent of N and K addition to rice indicating a saving of 33 per cent N and K to rice and N, P, K to wheat grown in a sequence. Among different SOM pools, WS-CHO and SMB-C and among N, P and S pools, SMB-P, Available-N and WS-OC were found to be the most important for rice and wheat production. The Roth-C-26.3 model could be used to predict the soil carbon dynamics as it fitted well with the observed data in the present experiment.