The water retention properties of biochar derived from broiler poultry litter as applied to the Botswana soil

Abstract

Crop farming in Botswana is very modest and of high risk compared to its neighboring countries because of significant dependency on reduced and unreliable rainfall and as a result of soils with poor water holding capacity and low cation exchange capacity. For this reason, only about two thirds of the available arable land are planted and of the planted land only about half is harvested, which translates into only one third of productive arable land. This study examines how addition of poultry litter (PL) biochar affects water retention properties of Botswana’s sandy soils. While many variables should be studied to fully comprehend this aspect, this paper exploits in detail, effects of biochar addition in reducing rate of water loss by evaporation. This work provides convincing evidence that addition of PL-derived biochar (as little as 10%) can significantly reduce water loss by evaporation, thus increasing water soil retention. It is demonstrated that water retention properties increase with increasing rate of biochar application. Two types PL-derived biochar were studied: (i) one with sunflower husks bedding and another (ii) with woodchips bedding. Though both biochars showed similar response to the test, the biochar with sunflower husks was slightly superior. Biochar also indicated significant hygroscopicity, when dried and left exposed to the atmosphere, as moisture content increased with increasing humidity. Based on initial indicators, further study should be done at laboratory and field scale to determine optimum conditions of biochar application in the quest to improve food security for Botswana, as well as improve employment and environmental goals of the country. A comprehensive further study should critically examine Field Capacity, Permanent Wilting Point, and Plant Available Water. As an ultimate goal, enhancing soil moisture retention properties of Botswana’s sandy soil enables to increase success rate in the traditional farming sector and, consequently, offers potential to accomplish “No Poverty” and “Zero Hunger” sustainable development goals.