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BACKGROUND: Ridge–furrow mulching farming systems (RFMs) aim to increase field productivity and improve water use efficiency. To explore environment‐friendly and efficient farming systems is a central aspect of rainfed wheat field management in Kenya where rainfall utilization is at a low level. We introduced RFMs (including plastic film and grass straw mulching) to semiarid Kenya to evaluate the effects on field productivity, rainwater utilization, soil quality and economic profitability using old and modern wheat cultivars from 2012 to 2013. RESULTS: Across the cultivars, the RFMs increased grain yield, aboveground biomass and water use efficiency by 74–163%, 36–104% and 89–273%, respectively, compared with conventional flat planting (control). RFMs significantly shortened the vegetative period while prolonging the reproductive period. The net economic output under RFMs was 74–165% higher than that of the control. Grass straw mulching achieved the highest economic output to input ratio, almost 45% higher than plastic film mulching, despite the former harvested only 82% of the maximum field productivity of the latter. Compared with the control, grass straw mulching promoted the contents of soil organic carbon, total nitrogen and C:N ratio by 14%, 8% and 5%, respectively, while obviously decreased values of these parameters were observed under plastic mulching. CONCLUSIONS: Through reducing soil water loss, and improving rainwater use efficiency and soil quality, ridge–furrow grass straw mulching would be a sustainable option for boosting field productivity and thus ensuring local food security in rainfed agricultural areas of Kenya. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In semiarid Kenya, field productivity of maize has been at a low integrity level due to insufficient use of rainwater use. From 2012 to 2013, an innovative ridge-furrow mulching system (RFMs) was tested using local maize ( Zea mays L.) hybrid, KCB in KARI-Katumani Farm, Kenya in long and short rainy seasons. Field experiments were conducted in a randomized complete block design with four treatments: 1) RFMs with transparent polyethylene film (RFT), 2) RFMs with black polyethylene film (RFB), 3) RFMs with grass straw mulching (RFS), and 4) RFMs without mulching (CK). Soil moisture & temperature, grain yield, water use and economic benefit were determined and analyzed. The results indicated that both RFT and RFB treatments significantly increased soil water storage amount in the depth of 0–60 cm. Grain yield and water use efficiency (WUE) in both treatments were increased by 66.5–349.9% and 72.9–382% respectively, compared with those of CK over two growing seasons. In addition, grain yield and WUE in RFS treatment were only increased by from 4.2–127.1% compared with those of CK. Particularly, two types of plastic films displayed different effects on modifying topsoil temperature. Transparent film mulching significantly increased topsoil temperature by 1.3 °C ( p < 0.05) higher than CK, to facilitate growth and grain formation in long (but cool) growing season. In contrast, black film mulching lowered soil temperature by 0.3 °C lower than CK in short (but warm) growing season, which led to better soil thermal balance. Overall, RFMs with film mulching could serve as an effective solution to increase maize productivity, and hence a promising strategy to cope with food security under climate change in semiarid Kenya. [ABSTRACT FROM AUTHOR]

• Maize yield responses to increasing planting densities were studied in RFM system. • Individual yield declined while population one increased first and then decreased. • This difference resulted from improved soil water availability as affected by RFM. • Optimal density had better trade-off between reproductive and vegetative growth. • Allometric R–V relationship explained density-dependent yield formation under RFM. The law of constant final yield and allometric theory have been seldom used to explore density-dependent yield formation and water use in rainfed farming systems, particularly in ridge-furrow mulching (RFM) system of maize. A two-year RFM field experiment was conducted using maize variety Yuyuan7879 in semiarid Kenya from 2015 to 2016, with four planting densities: 5.2 × 104 (D52, conventional density), 6.0 × 104 (D60), 6.9 × 104 (D69) and 8.5 × 104 (D85) plants per hectare. The grain yield and aboveground biomass per plant were significantly decreased with increasing density across two growing seasons. However, the population grain yield significantly was increased from D52 to D60 (from 3395.1–4471.7 kg ha−1) but declined significantly from D60 to D69 and D85 (p < 0.05) in 2015 and 2016, respectively. Meanwhile, the population aboveground biomass was significantly promoted from D52 to D60 (p < 0.05) and then remained relatively stable in D69 and D85, achieving a state of constant final yield. Under the improved soil storage, the RFM system raised the rational planting density from conventional D52 to D60 with regard to population yield. Water use efficiency for population yield (WUE G) was the highest at D52 and D60, followed by D69, and the lowest at D85. However, the WUE for the aboveground biomass (WUE A) was significantly lower in D52 than D60 and D85. Principal component analysis suggested that the population grain yield and WUE G were significantly positively associated with the reproductive allocation and leaf growth. This result was further affirmed by the allometric relationship between leaf biomass and body size, since the allometric exponent (<1) was raised with density. Allometric relationship between reproductive and vegetative mass demonstrated that the D60 treatment achieved a relatively balanced allocation of photosynthetic products into reproductive organs in comparison with other treatments. The RFM application significantly improved the availability of soil water, and the rational planting density of maize for better yield and WUE G. Thus, this phenomenon mechanically resulted from relatively better trade-offs between reproductive and vegetative growth, together with moderately increased leaf growth. [ABSTRACT FROM AUTHOR]

Spatial structural variations in ridge-furrow unit size and its ratio can result in the drastic fluctuation of soil hydrothermal status, and thereby affect water use and yield formation in dryland crops. Previous studies were little focused on the responses of dryland wheat productivity to the structural changes in ridge-furrow plastic mulching (RFM) system and its mechanism in semiarid eastern African Plateau (EAP). A two-year field experiment was conducted in Juja, a semiarid area in Kenya from 2015 to 2016. There were seven treatments of ridge-furrow width and ratios in randomized block design as follows: (1) 40 cm ridge width and 20 cm furrow width (R 4 F 2 , the same below), (2) R 3 F 2 , (3) R 2 F 2 , (4) R 3 F 4 , (5) R 2 F 4 , (6) R 3 F 6 and (7) R 2 F 6 , and conventional flat planting without mulching as control (CK). The results showed that R 4 F 2 , R 3 F 2 , R 2 F 2 , R 3 F 4 and R 2 F 4 treatments significantly improved soil water storage and temperature across two growing seasons compared with CK (P < 0.05). Among all the treatments, R 3 F 2 and R 2 F 2 obviously achieved the highest plant height, leaf area, aboveground biomass (AgB), grain yield and water use efficiency (WUE) (P < 0.05). Also, R 2 F 2 had the highest economic benefits in all treatments. The optimal ridge-furrow ratio appeared to be 1.32–1.38, 1.28–1.31, 1.39–1.49, 1.37–1.45 and 1.46–1.56 for wheat yield, AgB, WUE Y , WUE B and harvest index (HI), respectively. In addition, wheat yield, AgB, WUE and HI tended to decrease linearly with the increased ridge-furrow unit size. In conclusion, ridge-furrow ratio of 1–1.5 (R 2 F 2 to R 3 F 2) in combination with the minimum ridge-furrow unit size proved to be the optimum RFM system for the best dryland wheat productivity in accordance to regional soil and climate characteristics in semiarid EAP and other similar areas of the world. • RFM system significantly increased wheat productivity and WUE in semiarid EAP. • The optimal ridge-furrow ratio was 1.32–1.38 and 1.39–1.49 for yield and WUE. • Wheat yield and WUE decreased linearly with the increasing ridge-furrow unit size. • Ridge-furrow ratio of 1–1.5 combined with a minimum ridge-furrow unit was the optimum RFM system for wheat productivity. [ABSTRACT FROM AUTHOR]

Yield-phenology relation is a critical issue affecting rainfed maize field productivity in semiarid east African Plateau (EAP). We first introduced Chinese ridge-furrow mulching (RFM) system to EAP, using three maize cultivars with early-, mid- and late-maturing traits as test materials. A two-year field experiment was conducted in a semiarid farm of Kenya from 2012 to 2013. Three treatments were designed: alternative ridge and furrow with transparent plastic mulching (FT), with black plastic mulching (FB) and without mulching (CK). We found that FT and FB significantly increased soil moisture and accelerated crop maturity across two growing seasons. Leaf area and shoot biomass were increased by 30.2% and 67.5% in FT, 35.2% and 73.5% in FB, respectively, compared with CK. Grain yield, water use efficiency and economic output were increased by 55.6%, 57.5% and 26.7% in FT, and 50.8%, 53.3% and 19.8% in FB, respectively. Optimal yield and economic benefit were observed in late-maturing cultivar due to increased topsoil temperature in FT in 2012 (cool), and in early-maturing cultivar owing to cooling effect in FB in 2013 (warm). Our study suggested RFM system, combined with crop phenology selection, be a promising strategy to boost maize productivity and profitability in semiarid EAP.