Biochar soil amendment increases tomato seedling resistance to drought in sandy soils

Expanding aridity threatens agriculture in much of the world. Small farms (less than two hectares) produce 90% of the food in Eastern and Southern Africa and provide 70% of employment for women in the Least Developed Countries. Aridity thus endangers both food production and the employment of women. One possible solution is the addition of biochar, a highly porous pryrolysed biomass which is well documented to help retain water and nutrients in soils. Most current literature, however, proposes quantities of biochar which are beyond reach of small farms. The purpose of this research was thus to develop a method which would allow small amounts of biochar to provide significant protection for plants in their most vulnerable stage, the seedling. The test species was the cultivated tomato (Lycopersicon esculentum) because this is an important crop for subsistence farmers, and the seedlings are highly susceptible to drought. The results demonstrate that, in sandy substrates, 30% (v/v) biochar, concentrated in seedling root zones, significantly increases seedling resistance to wilting. Normal cooking can produce about 500 g of biochar a day and thus make possible increased wilting resistance for over 4000 tomato seedlings each year. This benefit is therefore within the reach of a demographic whose success is critically important to global sustainability.

► Small farms are vitally important for both feeding and for employing the world.
► In many areas, increasing aridity endangers both food production and employment.
► We present a method to enhance chances of seedling survival in semi-arid regions.
► This method is now available to individual subsistence families.