Impact of Rice Straw Mulch on Soil Physical Properties, Sunflower Root Distribution and Yield in a Salt-Affected Clay-Textured Soil

Priya Lal Chandra Paul,Enamul Kabir,Edward G Barrett-Lennard,Richard W Bell

doi:10.3390/agriculture11030264

Abstract

Puddling of clay soils for rice transplanting causes a loss of soil structure and vertical shrinkage cracks that are hypothesized to hamper sunflower root growth in the following dry season. To alleviate soil constraints for sunflower root growth and yield, we examined the effects of three levels of mulch and two irrigation regimes in the dry season on a clay-textured soil in the coastal zone of Bangladesh. These treatments were no-mulch, rice straw mulch at 5 t ha−1 and 10 t ha−1, irrigation applied to the field capacity (I1) and a water supply double that of the I1 treatment (I2). The rice straw mulch significantly increased soil water content by 3–9% and decreased soil penetration resistance by 28–77% and crack volume by 84–91% at A 0–30 cm soil depth relative to the no-mulch treatment. The better root development with the rice straw mulch increased sunflower yield by 23%. No benefit or further reduction in soil penetration resistance or yield improvement was obtained from increasing the level of mulch from 5 to 10 t ha−1 or the volume of irrigation water. It is concluded that ameliorating soil constraints by mulch application led to better root growth in the upper root zone and the increased yield in the clay soil.

Highlights

In the salt-affected coastal zone of the Ganges delta, as in many parts of Asia that grow wetland rice, puddling of clay soil through intensive tillage for rice establishment in the wet season damages soil structure, which during the following dry season leads to massive blocks of soil separated by abundant vertical shrinkage cracks [1,2]
An ideal soil pore space usually holds 25% water and 25% air by volume, but soil compaction due to puddled tillage with the dispersion of soil aggregates reduces the pore space in the dry season, which causes a dense soil with impeded internal drainage and aeration [5]
Data presented in this paper show that sunflower roots on clay soil are distributed according to several principles: (a) root dry mass, root length and root length density are greater at 0–20 cm than at depths in the soil profile, and mulches can increase root dry mass at 0–20 cm which increases grain yield; (b) roots can penetrate to considerable depths in this clayey, seasonally anaerobic soil; and (c) these effects occur despite or because of the presence of soil cracks and very high soil penetration resistances

Summary

Introduction

The puddled soils typically have an apedal structure, a compacted layer below the puddled layer and high soil strength when soil water decreases during the dry season [3,4]. An ideal soil pore space usually holds 25% water and 25% air by volume, but soil compaction due to puddled tillage with the dispersion of soil aggregates reduces the pore space in the dry season, which causes a dense soil with impeded internal drainage and aeration [5]. Cook [8], who conducted experiments in clay soil in growth chambers and the field at Los Banos, in the Philippines, reported that high soil penetration resistance in dry soil was the major soil physical constraint affecting the seedling emergence of mungbean

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