Effects of Paper-Mill Sludge as a Mulch versus Topsoil Incorporation on Potassium Uptake and the Grain Yield of Rain-Fed Wheat in a High Specific Surface Loess Soil with Illite Dominance in Clay Fraction

S Amini,S A R Movahedi Naeini,K Mashayekhi

doi:10.1155/2012/624824

Abstract

A field experiment with rain-fed winter wheat investigated the nutritional aspects of paper-mill sludge as a mulch and incorporated into the topsoil. Treatments with chemical fertilizers were also used as controls. Paper-mill sludge used as mulch with high rate (100 MG ha−1) and also the combined N and K mineral fertilizer treatments increased yield when a low potassium otherwise caused potassium deficiency in wheat with high specific surface soil. High soil Ca : K molar ratio by incorporation lowered potassium uptake and yield, with visual symptoms of potassium deficiency. A very high Gapon selectivity coefficient (KG) for K exchange against Ca + Mg (16.58 (L/mole)0.5) produced a nonlinear normalized exchange isotherm in favor of potassium with these soils containing high illite. Ca and K which are released by sludge decomposition are diverged in soil when mobilized by rain infiltration, lowering Ca : K molar ratio. Low soil Ca : K molar ratio may be expected by surface sludge application relative to incorporation, due to greater rain infiltration through upper soil layers and their effluent pore volumes per unit depth. Ca from triple superphosphate by the P, N, and K mineral fertilizers combined also reduced potassium uptake and yield relative to N and K combined.

Highlights

The application of organic residues at or near to the surface as mulches or incorporated in the topsoil influences the behavior of soil water and temperature regime and supplies additional nutrients for crop growth
Optimal application rate of sludge application for nutrient supply is less for mulch than incorporation. 100 t/ha sludge with 22.4% C by mulch application adds 1% OC to top 0.2 m surface soil with many benefits to arid and semiarid soils
Due to greater rain infiltration, traveling distance and divergence is greater for surface applied cations by mulch relative to incorporation

Summary

Introduction

The application of organic residues at or near to the surface as mulches or incorporated in the topsoil influences the behavior of soil water and temperature regime and supplies additional nutrients for crop growth. Limitations of phosphate supply and un-sustainability of fossil-fuel-based fertilizers and their transport cost add to the significance of organic residues for agricultural use [3]. They contain a large quantity of potassium [4]. Three different methods are used commercially to break down wood fiber (comprised principally of cellulosic compounds) mechanically or chemically to create wood pulp. Kraft mills use sodium hydroxide and sodium sulphide to break down the fibers, while sulphite mills use calcium sulfite, magnesium sulfite, or ammonium sulfite [5]. Many mills use chlorine to bleach the paper, while other mills use hydrogen peroxide [6]

Objectives

Methods

Results

Discussion

Conclusion