1.
Combining organic and mineral fertilizers as a climate-smart integrated soil fertility management practice in sub-Saharan Africa: A meta-analysis.
Gram, G, Roobroeck, D, Pypers, P, Six, J, Merckx, R, Vanlauwe, B
PloS one. 2020;(9):e0239552
Abstract
Low productivity and climate change require climate-smart agriculture (CSA) for sub-Saharan Africa (SSA), through (i) sustainably increasing crop productivity, (ii) enhancing the resilience of agricultural systems, and (iii) offsetting greenhouse gas emissions. We conducted a meta-analysis on experimental data to evaluate the contributions of combining organic and mineral nitrogen (N) applications to the three pillars of CSA for maize (Zea mays). Linear mixed effect modeling was carried out for; (i) grain productivity and agronomic efficiency of N (AE) inputs, (ii) inter-seasonal yield variability, and (iii) changes in soil organic carbon (SOC) content, while accounting for the quality of organic amendments and total N rates. Results showed that combined application of mineral and organic fertilizers leads to greater responses in productivity and AE as compared to sole applications when more than 100 kg N ha-1 is used with high-quality organic matter. For yield variability and SOC, no significant interactions were found when combining mineral and organic fertilizers. The variability of maize yields in soils amended with high-quality organic matter, except manure, was equal or smaller than for sole mineral fertilizer. Increases of SOC were only significant for organic inputs, and more pronounced for high-quality resources. For example, at a total N rate of 150 kg N ha-1 season-1, combining mineral fertilizer with the highest quality organic resources (50:50) increased AE by 20% and reduced SOC losses by 18% over 7 growing seasons as compared to sole mineral fertilizer. We conclude that combining organic and mineral N fertilizers can have significant positive effects on productivity and AE, but only improves the other two CSA pillars yield variability and SOC depending on organic resource input and quality. The findings of our meta-analysis help to tailor a climate smart integrated soil fertility management in SSA.
2.
What is the agronomic potential of biofertilizers for maize? A meta-analysis.
Schmidt, JE, Gaudin, ACM
FEMS microbiology ecology. 2018;(7)
Abstract
Biofertilizers are promoted as a strategy for sustainable intensification of agriculture, but their efficacy varies widely among published studies and it is unclear whether they deliver the promised benefits. Studies are commonly conducted under controlled conditions prior to deployment in the field, yet the predictive value of such studies for field-scale productivity has not been critically examined. A meta-analysis was conducted using a novel host crop-specific approach to evaluate the agronomic potential of bacterial biofertilizers for maize. Yield increases tended to be slightly higher and more variable in greenhouse studies using field soil than in the field, and greenhouse studies poorly predicted the influence of moderating climate, soil and taxonomic variables. We found greater efficacy of Azospirillum spp. and lower efficacy of Bacillus spp. and Enterobacter spp. under field conditions. Surprisingly, biofertilizer strains with confirmed plant-growth-promoting traits such as phosphorus solubilization, nitrogen fixation and phytohormone production in vitro were associated with lower yields in the field than strains not confirmed to possess these traits; only 1-aminocyclopropane-1-carboxylate deaminase synthesis increased yields. These results indicate the need for a novel biofertilizer development framework that integrates information from native soil microbial communities and prioritizes field validation of results.
3.
No-tillage effects on grain yield, N use efficiency, and nutrient runoff losses in paddy fields.
Liang, X, Zhang, H, He, M, Yuan, J, Xu, L, Tian, G
Environmental science and pollution research international. 2016;(21):21451-21459
Abstract
The effect of no-tillage (NT) on rice yield and nitrogen (N) behavior often varies considerably from individual studies. A meta-analysis was performed to assess quantitatively the effect of NT on rice yield and N uptake by rice, N use efficiency (NUE, i.e., fertilizer N recovery efficiency), and nutrient runoff losses. We obtained data from 74 rice-field experiments reported during the last three decades (1983-2013). Results showed the NT system brought a reduction of 3.8 % in the rice yield compared with conventional tillage (CT). Soil pH of 6.5-7.5 was favorable for the improvement of rice yield with the NT system, while a significant negative NT effect on rice yield was observed in sandy soils (p < 0.05). N rate, ranging from 120 to 180 kg N ha-1, for at least 3 years was necessary for NT to enable rice yield comparable with that of CT. Furthermore, the observations indicated NT reduced N uptake and NUE of the rice by 5.4 and 16.9 %, while increased the N and P exports via runoff by 15.4 and 40.1 % compared with CT, respectively. Seedling cast transplantation, N rate within the range 120-180 kg N ha-1, and employing NT for longer than 3 years should be encouraged to compromise between productivity and environmental effects of NT implementation in rice fields.
4.
A meta-analysis of responses of canopy photosynthetic conversion efficiency to environmental factors reveals major causes of yield gap.
Slattery, RA, Ainsworth, EA, Ort, DR
Journal of experimental botany. 2013;(12):3723-33
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Abstract
Improving plant energy conversion efficiency (εc) is crucial for increasing food and bioenergy crop production and yields. Using a meta-analysis, the effects of greenhouse gases, weather-related stresses projected to intensify due to climate change, and management practices including inputs, shading, and intercropping on εc were statistically quantified from 140 published studies to identify where improvements would have the largest impact on closing yield gaps. Variation in the response of εc to treatment type and dosage, plant characteristics, and growth conditions were also examined. Significant mean increases in εc were caused by elevated [CO2] (20%), shade (18%), and intercropping (15%). εc increased curvilinearly up to 55% with nitrogen additions whereas phosphorus application was most beneficial at low levels. Significant decreases in εc of -8.4% due to elevated [O3], -16.8% due to water stress, and -6.5% due to foliar damage were found. A non-significant decrease in εc of -17.3% was caused by temperature stress. These results identify the need to engineer greater stress tolerance and enhanced responses to positive factors such as [CO2] and nitrogen to improve average yields and yield potential. Optimizing management strategies will also enhance the benefits possible with intercropping, shade, and pest resilience. To determine optimal practices for εc improvement, further studies should be conducted in the field since several responses were exaggerated by non-field experimental conditions.