Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B1 and B2 vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B1 88 mg 100 g–1, B2 187 mg 100 g–1, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of welladapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Crossspecies grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations

Effect of improved fallow on crop productivity, soil fertility and climate-forcing gas emissions in semi-arid conditions

The impacts of fallow on soil fertility, crop production and climate-forcing gas emissions were determined in two contrasting legumes, Gliricidia sepium and Acacia colei, in comparison with traditional unamended fallow and continuous cultivation systems. After 2 years, the amount of foliar material produced did not differ between the two improved fallow species; however, grain yield was significantly elevated by 55% in the first and second cropping season after G. sepium compared with traditional fallow. By contrast, relative to the unamended fallow, a drop in grain yield was observed in the first cropping season after A. colei, followed by no improvement in the second. G. sepium had higher foliar N, K and Mg, while A. colei had lower foliar N but higher lignin and polyphenols. In the third year after fallow improvement, a simulated rainfall experiment was performed on soils to compare efflux of N2O and CO2. Improved fallow effects on soil nutrient composition and microbial activity were demonstrated through elevated N2O and CO2 efflux from soils in G. sepium fallows compared with other treatments. N2O emissions were around six times higher from this nitrogen-fixing soil treatment, evolving 69.9 ngN2O–N g−1soil h−1 after a simulated rainfall event, compared with only 8.5 and 4.8 ngN2O–N g−1soil h−1 from soil under traditional fallow and continuous cultivation, respectively. The findings indicate that selection of improved fallows for short-term fertility enhancement has implications for regional N2O emissions for dry land region

Residual effect of organic carbon as a tool for mitigating nitrogen oxides emissions in semi-arid climate

Abstract Residual effects of different fertilizers (mineral and organic) on the first pulses of carbon dioxide (C0 2 ), nitric oxide (NO), and nitrous oxide (N 2 0) after rewetting dry soil with or without application of a mineral N fertilizer were studied in a laboratory experiment. Six months before this study was conducted the fields had received either manure + urea, manure, urea or no fertilizer. In the first phase the soil was rewetted with water simulating a summer shower (heavy rainfall in short time) and in the second phase with a urea solution simulating a mineral fertilization. There were not significant differences in trace gas emissions between earlier field treatments after soil was rewetted with water addition. However, after urea addition, plots that had received manure 6 months earlier showed smaller total emissions of N 2 0 and NO compared to plots that had only received urea. The residual effect of manure can play an important role in carbon poor soils under arid-semiarid climate in mitigating atmospheric pollutants such us NO and N 2 0

Higher leaf nitrogen content is linked to tighter stomatalregulation of transpiration and more efficient water use acrossdryland trees

The least-cost economic theory of photosynthesis shows that water and nitrogen are mutu-ally substitutable resources to achieve a given carbon gain. However, vegetation in the Sahelhas to cope with the dual challenge imposed by drought and nutrient-poor soils.We addressed how variation in leaf nitrogen per area (Narea) modulates leaf oxygen andcarbon isotopic composition (δ18O,δ13C), as proxies of stomatal conductance and water-useefficiency, across 34 Sahelian woody species.Dryland species exhibited diverging leafδ18O andδ13C values, indicating large interspecificvariation in time-integrated stomatal conductance and water-use efficiency. Structural equa-tion modeling revealed that leaf Nareais a pivotal trait linked to multiple water-use traits. LeafNareawas positively linked to bothδ18O andδ13C, suggesting higher carboxylation capacityand tighter stomatal regulation of transpiration in N-rich species, which allows them toachieve higher water-use efficiency and more conservative water use.These adaptations represent a key physiological advantage of N-rich species, such aslegumes, that could contribute to their dominance across many dryland regions. This is thefirst report of a robust mechanistic link between leaf Nareaandδ18O in dryland vegetation that is consistent with core principles of plant physiology. δ13C, leafδ18O, plant isotopic composition,plant water-use strategies, Sahel, stomatalconductanc

Higher leaf nitrogen content is linked to tighter stomatalregulation of transpiration and more efficient water use acrossdryland trees

The least-cost economic theory of photosynthesis shows that water and nitrogen are mutu-ally substitutable resources to achieve a given carbon gain. However, vegetation in the Sahelhas to cope with the dual challenge imposed by drought and nutrient-poor soils.We addressed how variation in leaf nitrogen per area (Narea) modulates leaf oxygen andcarbon isotopic composition (δ18O,δ13C), as proxies of stomatal conductance and water-useefficiency, across 34 Sahelian woody species.Dryland species exhibited diverging leafδ18O andδ13C values, indicating large interspecificvariation in time-integrated stomatal conductance and water-use efficiency. Structural equa-tion modeling revealed that leaf Nareais a pivotal trait linked to multiple water-use traits. LeafNareawas positively linked to bothδ18O andδ13C, suggesting higher carboxylation capacityand tighter stomatal regulation of transpiration in N-rich species, which allows them toachieve higher water-use efficiency and more conservative water use.These adaptations represent a key physiological advantage of N-rich species, such aslegumes, that could contribute to their dominance across many dryland regions. This is thefirst report of a robust mechanistic link between leaf Nareaandδ18O in dryland vegetation that is consistent with core principles of plant physiology. δ13C, leafδ18O, plant isotopic composition,plant water-use strategies, Sahel, stomatalconductancepublishedVersio

Residual effect of organic carbon as a tool for mitigating nitrogen oxides emissions in semi-arid climate

Residual effects of different fertilizers (mineral and organic) on the first pulses of carbon dioxide (CO2), nitric oxide (NO), and nitrous oxide (N2O) after rewetting dry soil with or without application of a mineral N fertilizer were studied in a laboratory experiment. Six months before this study was conducted the fields had received either manure + urea, manure, urea or no fertilizer. In the first phase the soil was rewetted with water simulating a summer shower (heavy rainfall in short time) and in the second phase with a urea solution simulating a mineral fertilization. There were not significant differences in trace gas emissions between earlier field treatments after soil was rewetted with water addition. However, after urea addition, plots that had received manure 6 months earlier showed smaller total emissions of N2O and NO compared to plots that had only received urea. The residual effect of manure can play an important role in carbon poor soils under arid-semiarid climate in mitigating atmospheric pollutants such us NO and N2O