Addition of Biochar to a Sandy Desert Soil: Effect on Crop Growth, Water Retention and Selected Properties

Jeff J Schoenau,Khaled D Alotaibi

doi:10.3390/agronomy9060327

Abstract

Agricultural and environmental applications of biochar (BC) to soils have received increasing attention as a possible means of improving productivity and sustainability. Most previous studies have focused on tropical soils and more recently temperate soils. However, benefits of BC addition to desert soils where many productivity constraints exist, especially water limitations, have not been widely explored. Thus, three experiments were designed using a desert soil from Saudi Arabia to address three objectives: (1) to evaluate the effect of BCs produced from date palm residues added at 8 t ha−1 on wheat growth, (2) to determine the effect of BC addition and BC aging in soil on water retention, and (3) to reveal the effect of BC on selected soil physical (bulk density, BD; total porosity; TP) and chemical (pH; electrical conductivity, EC; organic matter, OM; cation exchange capacity, CEC) properties. The feedstock (FS) of date palm residues were pyrolyzed at 300, 400, 500, and 600 °C, referred to here as BC300, BC400, BC500, and BC600, respectively. The BC products produced at low temperatures were the most effective in promoting wheat growth when applied with the NPK fertilizer and in enhancing soil water retention, particularly with aging in soil, whereas high -temperature BCs better improved the selected soil physical properties. The low-temperature BCs increased the yield approximately by 19% and improved water retention by 46% when averaged across the incubation period. Higher water retention observed with low-temperature BCs can be related to an increased amount of oxygen-containing functional groups in the low-temperature BCs, rendering BC surfaces less hydrophobic. Only the BC300 treatment showed a consistent positive impact on pH, OM, and CEC. Pyrolysis temperature of date palm residue along with aging are key factors in determining the potential benefit of BC derived from date palm residues added to sandy desert soil.

Highlights

Biochar (BC) is a carbonaceous residue produced through the thermal breakdown of organic materials under limited conditions of oxygen
The BCs derived from date palm residues were more effective when combined with NPK fertilizer, and a better wheat response was evident with BCs produced at the lower temperatures of 300 and 400 ◦ C compared to those at 500 and 600 ◦ C
The results of the current study clearly indicated that the residence time of BC in soil and the pyrolysis temperature are significant factors in determining effect of BC on water retention

Summary

Introduction

Biochar (BC) is a carbonaceous residue produced through the thermal breakdown of organic materials under limited conditions of oxygen. The use of BC as a soil amendment is not a new concept, but it has received growing attention in the last few years, generally due to its role in mitigating greenhouse gas emissions by sequestering carbon in the soils, reducing nitrous oxide emissions, improving soil properties and quality, and increasing nutrient use efficiency and crop production [1,2,3,4]. BC can influence crop growth and yield directly via its effects on pH and nutrient retention and supply or indirectly through improvement of soil physical and chemical properties of importance for crop production [3,5,6,7]. The effect of BC on crop yield and plant nutrition was found to be variable, and its use as a sole amendment was not always effective, having its supplementation with mineral fertilizers sometimes necessary to promote crop growth [8,9,10,11,12,13,14,15,16]

Objectives

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Discussion

Conclusion