Tillage system and integrated soil fertility inputs improve smallholder farmers’ soil fertility and maize productivity in the Central Highlands of Kenya

We designed and implemented an on-farm trial in Meru South and Gatanga sub-counties to understand the effects of integrated soil fertility management (ISFM) technologies on soil nitrogen (N), phosphorus (P), potassium (K), and maize productivity. The technologies included combinations of mineral fertiliser and maize stover (CrMf); crop residue, Tithonia diversifolia and rock phosphate (CrTiP); crop residue, Tithonia diversifolia and goat manure (CrTiMan); crop residue, inorganic fertiliser and goat manure (CrMfMan); crop residue, goat manure and Dolichos lablab (CrManLeg), and sole inorganic fertiliser (Mf) executed under conventional (ConC) and minimum (MinTill) tillage methods. We interviewed the farmers who participated in implementing the trials at the end of the study to understand the likelihood to uptake the technologies. We observed that the technologies increased soil N, P, K, and maize productivity compared to ConC (the control). There was a high likelihood of uptake of high-performing ISFM technologies. We recommend CrTiP for the two sub-counties for the short-term. However, a long-term experiment is needed to evaluate performances of CrTiMan, CrTiP, CrMfMan, and CrManLeg under the two tillage methods for site-specific recommendations taking into consideration rainfall variations

Soil Organic Carbon Stocks under Different Land Utilization Types in Western Kenya

The up-surging population in sub-Saharan Africa (SSA) has led to the conversion of more land for agricultural purposes. Resilient land utilization types that input carbon to the soil are key in enhancing climate change mitigation. However, there are limited data on different land utilization types’ contribution to climate mitigation through carbon input to soils. The study aims to quantify carbon stock across different land utilization types (LUT) practiced in Western Kenya. The following land utilization types were studied: agroforestry M (agroforestry with Markhamia lutea), sole sorghum, agroforestry L (agroforestry with Leucaena leucocephalaI), sole maize, and grazing land replicated thrice. To determine soil bulk density, SOC concentration, and soil carbon stock, soil samples were collected at depths of 0–5, 5–10, 10–20, and 20–30 cm from different LUTs. A PROC ANOVA was used to determine the difference in soil bulk density, SOC, and SOC stock between different LUTs and depths. The four variables differed across the LUTs and depths. A high soil bulk density was observed at 0–5 cm under grazing land (1.6 g cm−3) and the lowest under agroforestry M (1.30 g cm−3). Conversely, the soil bulk density was low at 20–30 cm under grazing land. The 0–5 cm depth accounted for a high share of SOC and SOC stock under Agroforestry M, while the 10–20 and 20–30 cm depth accounted for the high share of SOC stock under agroforestry L. The study showed differences in SOC across the different depths and LUTs. The findings highlight that agroforestry L and agroforestry M are promising interventions toward climate mitigation through carbon induction to soils