POTASSIUM DYNAMICS, USE EFFICIENCY AND BALANCE IN CALCAREOUS SOILS AFTER FIFTEEN YEARS CONSERVATION AGRICULTURE UNDER RICE-WHEAT CROPPING SYSTEM
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Date
2021
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DRPCAU, PUSA
Abstract
Rice wheat cropping system (RWCS) is the main fundamental for employment, livelihood and income for the people in Indo Gangetic Plains (IGP) regions of our India, Pakistan,Nepal and Bangladesh. The area covered by all these countries under IGP is 13.5 mha. Out of this 10.5m ha is under India only and it contributes 40% of country’s total food basket. With introduction of high yielding varieties (HYV’s) through green revolution, the productivity of RWCS in these regions was remarkably increased. The intensive practices of cultivation lead to inadequate replenishment and heavy removal of nutrients and resulted in deficiencies and depletion of nutrient reserves in soil. In these types of uneven situations, change of farming system from conventional to conservation agriculture will help in maintaining the soil health with care from which plant getting its requirements. The straw is a rich source of potassium and also its availability varies with tillage practices, so the present study on “Potassium dynamics, use efficiency and balance in calcareous soils after fifteen years conservation agriculture under rice-wheat cropping system” was carried out in randomised block design with 3 replications and 11 different treatments combinations of conservation agriculture practices during kharif-2020 under a long term trial of BISA-CIMMYT, Pusa running since kharif-2006. The different treatments were T1:Puddled and Transplanted Rice –Conventionally Tilled Wheat (PuTR-CTW), T2:Puddled and Transplanted Rice-Zero/No Tilled Wheat (PuTr-
ZTW), T3: Permanent Beds of Directly Seeded Rice-Permanent Beds of Directly Drilled wheat (PBDSR-PBDDW); T4: Permanent Beds of Directly Seeded Rice-Permanent Beds of Directly Drilled wheat- First time intensive tillage after 15 years of no tillage and then fresh beds of Directly Seeded rice and wheat every year (PBDSR-PBDDW-ITDSRW), T5:Zero/No-Tilled Direct Seeded Rice-Conventionally Tilled Wheat (ZTDSR-CTW), T6: Zero/No-Tilled Direct Seeded Rice-Zero/No-Tilled Wheat Without Residue (ZTDSR-(ZTW-R)), T7: Zero/No-Tilled Direct Seeded Rice-Zero/No Tilled Wheat Without Residue-Intensive Tillage after 15 years and then continuing the tillage for Direct Seeded rice and wheat every year (ZTDSR-(ZTW-R)-(CTDSR-CTW)every year), T8: Zero Tilled Direct Seeded Rice-Zero Tilled Wheat with Residue Retention (ZTDSR-(ZTW+R)), T9: Zero/No-Tilled Direct Seeded Rice-Zero/No Tilled Wheat With Residue-Intensive Tillage after 15 years and then continuing the tillage for Direct Seeded rice and wheat With Residue Retention every year (ZTDSR-(ZTW+R)-CTDSR-(CTW+R)every year), T10:Unpuddled Transplanted Rice-Zero Tilled Wheat (UPTR-ZTW) and T11: Zero Tilled Rice- Sesbania Brown Manure-Zero Tillage Wheat (before 2010,Wet Direct seeded Rice(WDSR)-Zero tilled Wheat rotation was practiced (ZTR-BM-ZTW). The results indicate that available K and water soluble K was maximum in surface soil and declined with depth. Intensive tillage after 15 years did not show any significant changes in rice yield over their respective untilled one treatment. But, significant increase in K availability in the intensive tilled plots without crop residue retention was recorded, while, it declined significantly under the intensive tilled plots with crop residue retention. Crop residue retention enhanced the potassium content and uptake by the rice crop and also helps in the partitioning of K more towards de-husked rice grain than the husk. In all the treatments, overall contribution of muscovite mineral K was highest (52%) followed by feldspar (42%) and biotite (6%). Significant and positive correlation among various forms of K indicates dynamic equilibrium in soil.Application of crop residue with conservation tillage improved the potassium use efficiency than the conventional method. The negative potassium balance was observed under all the treatments but its intensity was low in the treatment where conservation tillage practices with crop residue retention was followed in comparison to conventional method. Thus, conservation agriculture practices with no tillage and crop residue retention is a good option for enhanced crop productivity and improved potassium dynamics and its balance in soil.