Dual plastic film and straw mulching boosts wheat productivity and soil quality under the El Nino in semiarid Kenya.

The extreme climate events such as El Nino seriously threaten crop production and agro-ecological sustainability because of the aggravated environmental stresses worldwide, particularly in sub-Saharan Africa. To address this issue, we investigated the effects of dual plastic film and straw mulching in ridge-furrow (RF) system on wheat productivity, soil carbon and nitrogen stocks in a semiarid area in Kenya from 2015 to 2017. The experimental site represents a typical semiarid continental monsoon climate, and soil type is chromic vertisols. Field experiment with randomized block design consisted of six RF treatments as follows: 1) dual black plastic film and straw mulching (RFbS), 2) dual transparent plastic film and straw mulching (RFtS), 3) sole black plastic film mulching (RFb), 4) sole transparent plastic mulching RF (RFt), 5) sole straw mulching (RFS) and 6) no mulching (CK). The results indicated that seasonal dynamics of rainfall and air temperature fit in with the weather type of El Nino over four growing seasons. RFbS, RFtS, RFb and RFt significantly increased soil water storage (SWS), topsoil temperature, aboveground biomass, grain yield and water use efficiency across four growing seasons (p < 0.05) as compared with CK. Among all the treatments, RFbS and RFtS achieved the greatest SWS, AgB, grain yield and WUE, owing to improved soil hydro-thermal status in both treatments. Critically, RFbS and RFtS significantly improved soil organic carbon and total nitrogen, soil bulk density and the C:N ratio following four growing seasons, comparing with other treatments (p < 0.05). Besides, RFbS and RFtS gave the highest economic returns among all treatments. For the first time, we found that dual plastic film and straw mulching could serve as a sustainable land management to boost wheat productivity and improve soil quality under El Nino in semiarid areas of SSA.

Yield-phenology relations and water use efficiency of maize (Zea mays L.) in ridge-furrow mulching system in semiarid east African Plateau.

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.

Methylation mediated by an anthocyanin, O-methyltransferase, is involved in purple flower coloration in Paeonia.

Anthocyanins are major pigments in plants. Methylation plays a role in the diversity and stability of anthocyanins. However, the contribution of anthocyanin methylation to flower coloration is still unclear. We identified two homologous anthocyanin O-methyltransferase (AOMT) genes from purple-flowered (PsAOMT) and red-flowered (PtAOMT) Paeonia plants, and we performed functional analyses of the two genes in vitro and in vivo. The critical amino acids for AOMT catalytic activity were studied by site-directed mutagenesis. We showed that the recombinant proteins, PsAOMT and PtAOMT, had identical substrate preferences towards anthocyanins. The methylation activity of PsAOMT was 60 times higher than that of PtAOMT in vitro. Interestingly, this vast difference in catalytic activity appeared to result from a single amino acid residue substitution at position 87 (arginine to leucine). There were significant differences between the 35S::PsAOMT transgenic tobacco and control flowers in relation to their chromatic parameters, which further confirmed the function of PsAOMT in vivo. The expression levels of the two homologous AOMT genes were consistent with anthocyanin accumulation in petals. We conclude that AOMTs are responsible for the methylation of cyanidin glycosides in Paeonia plants and play an important role in purple coloration in Paeonia spp.