Water Infiltration and Moisture in Soils under Conservation and Conventional Agriculture in Agro-Ecological Zone IIa, Zambia

Conservation agriculture is often presented as being ‘climate smart’ due to anticipated increases in soil moisture. The extent of enhanced water availability in farmers’ fields is, however, poorly documented. This paper presents five data sets describing soil moisture in fields of small-scale conservation and conventional farmers in the Agro-ecological Zone IIa, Zambia. The data include (1) soil cover; (2) time required for visible soil surface saturation, ponding and initial runoff under artificial rainfall; (3) saturated water infiltration rates; (4) weekly soil moisture at six soil depths for two entire rain seasons; and (5) weekly rainfall in each field. Measurements were done for 15 pairs of comparable fields under conservation and conventional agriculture. Pairwise analysis showed significantly shorter time for surface saturation, ponding, and runoff in conservation fields compared to conventional fields. Saturated infiltration rates in riplines and basins of conservation fields were similar to rates in ploughed/hoed fields. Infiltration rates between riplines and between basins were 31–37% lower than those in ploughed/hoed fields. Soil moisture in riplines and basins of conservation fields was higher by an average factor of 1.08 down to 40 cm soil depth, whereas it was lower by an average factor of 0.89 between plant rows compared to fields under conventional tillage. Based on 34,000 soil moisture measurements from 0 to 60 cm depth over two seasons, soils in conservation fields contained a weighted average of 18.2% (vol.) water compared to 19.9% (vol.) in conventional fields (p < 0.05). The results indicate that small-scale adopters of conservation agriculture are less ‘climate smart’ than conventional farmers in terms of water infiltration and soil moisture.