Repositorio Nacional

Can farmers in sub-Saharan Africa (SSA) boost crop yields and improve food availability without using more mineral fertilizer? This question has been at the center of lively debates among the civil society, policy-makers, and in academic editorials. Proponents of the “yes” answer have put forward the “input reduction” principle of agroecology, i.e. by relying on agrobiodiversity, recycling and better efficiency, agroecological practices such as the use of legumes and manure can increase crop productivity without the need for more mineral fertilizer. We reviewed decades of scientific literature on nutrient balances in SSA, biological nitrogen fixation of tropical legumes, manure production and use in smallholder farming systems, and the environmental impact of mineral fertilizer. Our analyses show that more mineral fertilizer is needed in SSA for five reasons: (i) the starting point in SSA is that agricultural production is “agroecological” by default, that is, very low mineral fertilizer use, widespread mixed crop-livestock systems and large crop diversity including legumes, but leading to poor soil fertility as a result of widespread soil nutrient mining, (ii) the nitrogen needs of crops cannot be adequately met solely through biological nitrogen fixation by legumes and recycling of animal manure, (iii) other nutrients like phosphorus and potassium need to be replaced continuously, (iv) mineral fertilizers, if used appropriately, cause little harm to the environment, and (v) reducing the use of mineral fertilizers would hamper productivity gains and contribute indirectly to agricultural expansion and to deforestation. Yet, the agroecological principles directly related to soil fertility—recycling, efficiency, diversity—remain key in improving soil health and nutrient-use efficiency, and are critical to sustaining crop productivity in the long run. We argue for a nuanced position that acknowledges the critical need for more mineral fertilizers in SSA, in combination with the use of agroecological practices and adequate policy support.

Manure Crop Yields Smallholder Farming Systems Environmental Hazards CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA BIOLOGICAL NITROGEN FIXATION LEGUMES NUTRIENT BALANCE SOIL FERTILITY AGROECOLOGY YIELD INCREASES LITERATURE REVIEWS

Agroecology can promote climate change adaptation outcomes without compromising yield in smallholder systems

Sieglinde Snapp Yodit Kebede Eva Wollenberg (2023, [Artículo])

A critical question is whether agroecology can promote climate change mitigation and adaptation outcomes without compromising food security. We assessed the outcomes of smallholder agricultural systems and practices in low- and middle-income countries (LMICs) against 35 mitigation, adaptation, and yield indicators by reviewing 50 articles with 77 cases of agroecological treatments relative to a baseline of conventional practices. Crop yields were higher for 63% of cases reporting yields. Crop diversity, income diversity, net income, reduced income variability, nutrient regulation, and reduced pest infestation, indicators of adaptative capacity, were associated with 70% or more of cases. Limited information on climate change mitigation, such as greenhouse gas emissions and carbon sequestration impacts, was available. Overall, the evidence indicates that use of organic nutrient sources, diversifying systems with legumes and integrated pest management lead to climate change adaptation in multiple contexts. Landscape mosaics, biological control (e.g., enhancement of beneficial organisms) and field sanitation measures do not yet have sufficient evidence based on this review. Widespread adoption of agroecological practices and system transformations shows promise to contribute to climate change services and food security in LMICs. Gaps in adaptation and mitigation strategies and areas for policy and research interventions are finally discussed.

CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA CLIMATE CHANGE CROPS FOOD SUPPLY GAS EMISSIONS GREENHOUSE GASES FARMING SYSTEMS AGROECOLOGY FOOD SECURITY LESS FAVOURED AREAS SMALLHOLDERS YIELDS NUTRIENTS BIOLOGICAL PEST CONTROL CARBON SEQUESTRATION LEGUMES

Metabolites Profile of Extracts and Fractions of Erythroxylum mexicanum Kunth by UHPLC-QTOF-MS/MS and its Antibacterial, Cytotoxic and Nitric Oxide Inhibitory Activities

LAURA PATRICIA ALVAREZ BERBER MARIA DE LOS ANGELES RAMIREZ CISNEROS (2024, [Artículo])

The present study shows the untargeted metabolite profiling and in vitro antibacterial, cytotoxic, and nitric oxide (NO) inhibitory activities of the methanolic leaves extract (MLE) and methanolic stem extract (MSE) of Erythroxylum mexicanum, as well as the fractions from MSE. Using ultra-high performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (UHPLC-QTOF-MS/MS), a total of 70 metabolites were identified; mainly alkaloids in the MLE, while the MSE showed a high abundance of diterpenoids. The MSE fractions exhibited differential activity against Gram-positive bacteria. Notably, the hexane fraction (HSF) against Streptococcus pyogenes ATCC 19615 (MIC=62.5 µg/mL) exhibited a bactericidal effect. The MSE fractions exhibited cytotoxicity against all cancer cell lines tested, with selectivity towards them compared to a noncancerous cell line. Particularly, the HSF and chloroform fraction (CSF) showed the highest cytotoxicity against prostate cancer (PC-3) cells, with IC50 values of 19.9 and 18.1 µg/mL and selectivity indexes of 3.8 and 4.2, respectively. Both the HSF and ethyl acetate (EASF) fractions of the MSE inhibited NO production in RAW 264.7 macrophages, with NO production percentages of 50.0% and 51.7%, respectively, at a concentration of 30 µg/mL. These results indicated that E. mexicanum can be a source of antibacterial, cytotoxic, and anti-inflammatory metabolites.

BIOLOGÍA Y QUÍMICA QUÍMICA MS analysis • diterpenoids • biological activities