Effect of Mulching on Soil Temperature and Moisture for Potato Production in Agro-ecological Zones of Central Highlands of Kenya

Abstract

In Kenya, potato plays a significant role in the livelihood of smallholder farmers, serving both as a food security and cash crop. Sensitive to both heat and moisture stress, in the tropics the future of potato production is threatened by global warming and the associated changes in temperatures and rainfall variability. A study to determine the potential of mulching as an adaptation strategy to climate change in potato production system was undertaken along an elevation gradient of varying agroecological zones (AEZs) in the south eastern slopes of Mt. Kenya in Embu County. The study sites were Mbuvori, representing the lower highland humid (LH1), at 1900–2100 m.a.s.l.; Nembure, the upper midland subhumid (UM2), at 1400–1600 m.a.s.l.; and Karurumo, the lower midlands semihumid (LM3), at 1070–1280 m.a.s.l. AEZs. Dry maize stover was applied at the rate of 0, 4, 8, and 12 t ha⁻¹. The experiment was laid out in a RCBD and was replicated three times per site. Soil temperature measurements were taken at depths of 12 and 20 cm at 8.00 to 9.00 and 14.00 to 15.00 h and gravimetric soil moisture determined at 0–15 cm depth. Potato emergence and yield were also monitored. The results showed that application of 12 t ha⁻¹ of maize stover significantly improved soil moisture, at Karurumo and during period of less rainfall in the other two sites. Mulching rates interacted well with soil temperature, whereby with increasing quantities of mulch, the temperature gap between the hot and drier AEZs sites and the cooler zones decreased. At 12 cm depth, mulching reduced afternoon soil temperatures at Nembure to levels that were comparable to those observed in the cool and moist Mbuvori site and was negatively correlated to increasing mulch quantities. At 20 cm depth, soil temperature in plots applied with 12 t ha⁻¹ mulching rate, at Karurumo, was comparable to that observed at Nembure, while the difference between the two sites in bare soil was as high as 5.5 °C. Mulching reduced the gap between soil temperature observed between Karurumo and Mbuvori. The gap between the two sites bare soil plots ranged between 5.0 °C and 7.8 °C while that beneath the 12 t ha⁻¹ was 2.3 °C. At Karurumo, afternoon soil temperature at both 12 cm and 20 cm depths was negatively correlated to increasing mulching rate (p <0.05). Mulching enhanced tuber emergence at Karurumo. Application of 8 and 12 t ha⁻¹ resulted in increased tuber yield at both Nembure and Karurumo. This study shows that mulching can be a reliable adaptation strategy to climate change in smallholder potato production system of Kenya.