Zinc and Carbon pools under long term conservation agriculture with Rice-Wheat cropping system in Calcareous Soil
Loading...
Date
2018
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Dr. Rajendra Prasad Central Agricultural University, Pusa (Samastipur)
Abstract
A long-term experiment involving various combinations of tillage, crop establishment and residue management practices in a rice-wheat rotation has been continuing since 2006 at South Pangabri plot of Crop Research Center, Dr. Rajendra Prasad Central Agricultural University, Pusa, Samastipur, Bihar. The climate of this region is sub-tropical humid. The experimental site is situated at 25°30' N latitude, 85°40' E longitude and 52.00 meter above mean sea level.
Conservation agriculture based on principles of minimum soil disturbance, residue retention on soil surface and crop diversification improves soil organic carbon and available nutrients status which plays a crucial role in sustaining the soil health. Therefore present study entitled “Zinc and Carbon pools under long-term conservation agriculture with Rice-Wheat cropping system in Calcareous soil", was undertaken during kharif 2016 and rabi 2016-17. The objectives were to understand the effect of conservation agriculture on rice and wheat yield and uptake of nutrients; zinc fractions in soil; different forms of carbon in soil, and; soil chemical properties.
The experiment was laid out in a randomized block design with 8 treatments with different crop establishment practices and residue retention in rice and wheat. Rice grain yield in conventional tillage practices in both rice and wheat crop [PTR-CTW] was significantly lower than most of the treatments. Higher grain and straw yield of both rice and wheat was obtained in zero tillage wheat crop preceded by zero tillage rice with residue retention in both the crops. Total soil organic carbon (TOC) in 0-5 cm soil depth, under zero tillage rice- zero tillage wheat on bed with residue [ZTR-ZTW(B)+R] and zero tillage rice-zero tillage wheat with residue[ZTR-ZTW+R] were 23.79g kg-1 and 23.11g kg-1 respectively, which were statistically at par to each other These values were significantly higher over conventional tillage [PTR-CTW] treatments (10.55 gkg-1). TOC of 5-15cm and 15-30cm depth under
ZTR-ZTW(B)+R treatment was also significantly superior over PTR-CTW. The Walkley and Black carbon (WBC) under treatment ZTR-ZTW+R was 1.10% which was 72.9 % higher over PTR-CTW at 0-5 cm depth. Different fractions of oxidisable carbon of varying lability in 0-5cm, 5-15 cm and 15-30 cm was found in the order: Non-labile > Very labile > Labile > Less labile. The content of TOC, WBC, Microbial biomass carbon and KMnO4 - C decreased with increase in soil depth while that of soil inorganic carbon increased. Correlation study among different fractions of oxidisable carbon indicated that all forms of oxidisable carbon were in dynamic equilibrium and positively and significantly correlated with each other.
The water soluble and exchangeable fractions of zinc under ZTR-ZTW(B)+R and ZTR-R were statistically at par to each other and were statistically superior over PTR-CTW. Correlation study among different fractions of zinc and soil properties like organic carbon, CaCO3 content and grain and straw yield,zinc uptake by rice and wheat indicated that the Water soluble + Exchangeable-Zn, Complexed-Zn and Organically bound-Zn, Residual-Zn were positively and significantly correlated with all the parameters except CaCO3 content of soil. The path analysis was carried out to study the direct and indirect effect of different zinc fractions towards available zinc in soil and zinc uptake by both the crops. Different fractions of zinc in soil was found in the dominance order: Residual-Zn > Crystalline oxide bound- Zn >Complexed-Zn > Amorphous oxide bound- Zn > organically bound-Zn > Water soluble + Exchangeable-Zn.
It may be concluded that zero tillage rice followed by zero tillage wheat with residue retention in rice had similar system rice equivalent yield. The different organic carbon fractions e.g. TOC, WBC, MBC, POC and the different labile pools were similar in ZTR-ZTW(B)+R and ZTR-ZTW +R treatments. The values were significantly higher as compared to other treatments. The dissolution of free CaCO3 in both these treatmentswere also significantly higher as compared to the other treatments. Water soluble + Exchangeable-Zn, Complexed-Zn and Organically bound-Zn were dominant fractions of zinc in soil that contributed most towards uptake of Zn by rice and wheat crop.
Description
Keywords
null