Conservation of soil organic carbon, biodiversity and the provision of other ecosystem services along climatic gradients in West Africa

Terrestrial carbon resources are major drivers of development in West Africa. The distribution of these resources co-varies with ecosystem type and rainfall along a strong Northeast-Southwest climatic gradient. Soil organic carbon, a strong indicator of soil quality, has been severely depleted in some areas by human activities, which leads to issues of soil erosion and desertification, but this trend can be altered with appropriate management. There is significant potential to enhance existing soil carbon stores in West Africa, with benefits at the global and local scale, for atmospheric CO2 mitigation as well as supporting and provisioning ecosystem services. Three key factors impacting carbon stocks are addressed in this review: climate, biotic factors, and human activities. Climate risks must be considered in a framework of global change, especially in West Africa, where landscape managers have few resources available to adapt to climatic perturbations. Among biotic factors, biodiversity conservation paired with carbon conservation may provide a pathway to sustainable development, and biodiversity conservation is also a global priority with local benefits for ecosystem resilience, biomass productivity, and provisioning services such as foodstuffs. Finally, human management has largely been responsible for reduced carbon stocks, but this trend can be reversed through the implementation of appropriate carbon conservation strategies in the agricultural sector, as shown by multiple studies. Owing to the strong regional climatic gradient, country-level initiatives will need to consider carbon sequestration approaches for multiple ecosystem types. Given the diversity of environments, global policies must be adapted and strategies developed at the national or sub-national levels to improve carbon storage above and belowground. Initiatives of this sort must act locally at farmer scale, and focus on ecosystem services rather than on carbon sequestration solely

Constant temperatures and the rate of seed germination in maize (Zea mays L.) of contrasting endosperm

The germination of quality protein maize (QPM) cultivar, Obatanpa, was compared to normal endosperm (NEM) cultivar, Okomasa, on a temperature gradient plate at constant temperatures ranging from 15-45 oC. Germination occurred at all temperatures except at 42.5 oC for the QPM cultivar and 45 oC for the NEM cultivar. The rate of germination of the NEM cultivar was faster than that of the QPM cultivar at all temperatures. The thermal times for median germination were 46 for QPM and 40.7 oCd for the NEM cultivar. The cardinal temperatures (base, Tb, optimum, To and ceiling, Tc) for the NEM cultivar were Tb: 7, To: 30 and Tc: 48.2 oC. The corresponding values for the QPM cultivar were Tb: 7.6, To: 27.5 and Tc: 43.4 oC. The base and optimal temperatures were not significantly different but the ceiling temperature for the QPM was significantly lower(

Conservation of soil organic carbon, biodiversity and the provision of other ecosystem services along climatic gradients in West Africa

Terrestrial carbon resources are major drivers of development in West Africa. The distribution of these resources co-varies with ecosystem type and rainfall along a strong Northeast-Southwest climatic gradient. Soil organic carbon, a strong indicator of soil quality, has been severely depleted in some areas by human activities, which leads to issues of soil erosion and desertification, but this trend can be altered with appropriate management. There is significant potential to enhance existing soil carbon stores in West Africa, with benefits at the global and local scale, for atmospheric CO2 mitigation as well as supporting and provisioning ecosystem services. Three key factors impacting carbon stocks are addressed in this review: climate, biotic factors, and human activities. Climate risks must be considered in a framework of global change, especially in West Africa, where landscape managers have few resources available to adapt to climatic perturbations. Among biotic factors, biodiversity conservation paired with carbon conservation may provide a pathway to sustainable development, and biodiversity conservation is also a global priority with local benefits for ecosystem resilience, biomass productivity, and provisioning services such as foodstuffs. Finally, human management has largely been responsible for reduced carbon stocks, but this trend can be reversed through the implementation of appropriate carbon conservation strategies in the agricultural sector, as shown by multiple studies. Owing to the strong regional climatic gradient, country-level initiatives will need to consider carbon sequestration approaches for multiple ecosystem types. Given the diversity of environments, global policies must be adapted and strategies developed at the national or sub-national levels to improve carbon storage above and belowground. Initiatives of this sort must act locally at farmer scale, and focus on ecosystem services rather than on carbon sequestration solely

Corn growth and yield in competition with weeds Crescimento e rendimentos do milho em competição com plantas daninhas

Although labor is intensive, evaluating the growth of crops may allow a better understanding of crop performance, including the reasons why certain cultivars can compete better with weeds. This study aims at evaluating growth, green ear yield, and grain yield in corn when in competition with weeds. Cultivars AG 1051 and BRS 106 were grown with (two hoeings, at 20 and 40 days after sowing) or without weed control. In order to evaluate crop growth, six collections of the above-ground part and the root system of corn were performed, every 15 days, with the first collection made 30 days after sowing. A randomized complete block design was adopted, with split-split plots (weed control in plots, cultivars in subplots, and collections in sub-subplots) and ten replicates. Eighteen weed species were found in the experiment area. Increased values of corn leaf area, above-ground part and root system, due to plant age function, were smaller in non-hoed plots than in hoed plots and were dependent upon cultivar. The lack of weed control increased dry matter of weeds aboveground part and decreased green ear yield and grain yield. Cultivar AG 1051 had higher increases in leaf area, above-ground part of the plant and root system, due to plant age function, and controlled weeds better than cultivar BRS 106. In addition, cultivar AG 1051 was superior to other cultivars with respect to most traits used for green corn yield and grain yield assessment.<br>A avaliação do crescimento das culturas, embora trabalhosa, pode possibilitar o melhor entendimento do desempenho das culturas, inclusive das razões pelas quais determinadas cultivares são capazes de competir melhor com as plantas daninhas. O trabalho teve como objetivo avaliar o crescimento e os rendimentos de espigas verdes e de grãos do milho, em competição com plantas daninhas. As cultivares AG 1051 e BRS 106 foram cultivadas com duas capinas (aos 20 e 40 dias após a semeadura) e sem controle de plantas daninhas. Para avaliação do crescimento da cultura, foram realizadas seis coletas da parte aérea e do sistema radicular do milho, de 15 em 15 dias, a primeira sendo efetuada 30 dias após a semeadura. Utilizou-se o delineamento de blocos completos casualizados, com parcelas sub-subdivididas (controle de plantas daninhas nas parcelas, cultivares nas subparcelas e coletas nas sub-subparcelas) e dez repetições. Dezoito espécies de plantas daninhas ocorreram na área experimental. Os aumentos da área foliar, da parte aérea e do sistema radicular do milho, em função da idade, foram menores em parcelas não capinadas do que nas parcelas capinadas e dependeram das cultivares. A falta de controle das plantas daninhas aumentou a matéria seca da parte aérea das plantas daninhas e reduziu os rendimentos de espigas verdes e de grãos. A cultivar AG 1051 apresentou maiores aumentos da área foliar, da parte aérea da planta e do sistema radicular, em função da idade da planta, e controlou melhor as plantas daninhas, que a cultivar BRS 106. Além disso, a cultivar AG 1051 foi superior à outra cultivar, quanto à maioria das características utilizadas na avaliação do rendimento de milho verde e quanto ao rendimento de grãos

Growth and yield of corn grain and green ear in competition with weeds Crescimento e rendimento de espigas verdes e de grãos de milho em competição com plantas daninhas

Studies on plant growth are interesting because they provide explanations for the factors that influence yield in various crops. The objective of this work was to evaluate growth and yield in corn cultivar AG1051, when in competition with weeds. Cultivar AG 1051 was submitted to two groups of treatments: weed control, and sampling periods for dry biomass evaluation. The weed control treatments consisted of hoeing (two hoeings performed at 20 and 40 days after sowing) and no hoeing. Sampling periods consisted of collecting the above-ground part and roots of corn every fifteen days, until 105 days after sowing (DAS); the first sampling was performed 30 DAS. A completely randomized block design with ten replicates was used. For the characteristics evaluated in a single season, statistical analyses were carried out as a random block experiment. For the characteristics evaluated in several periods, statistical analyses were carried out as random blocks with split-plots (weed control assigned to plots). Fourteen weed species, unevenly distributed throughout the experimental area, were the most important. The growth observed for the above-ground part and root system of corn was 30% smaller in the non-hoed plots, compared to the hoed plots. Lack of weed control increased dry matter of the above-ground part of the weeds and reduced the number of unhusked and husked marketable green ears by 23% and 49%, respectively. Grain yield reduction caused by lack of weed control reached 38%.<br>Apesar de trabalhosos, os estudos sobre o crescimento são de interesse porque fornecem explicações sobre os fatores que influenciam o rendimento das culturas. O objetivo do presente trabalho foi avaliar o crescimento e o rendimento de espigas verdes e de grãos do cultivar de milho AG 1051, em competição com plantas daninhas. Esse cultivar foi submetido a dois grupos de tratamento: controle de plantas daninhas e épocas de amostragem para avaliação da biomassa seca. Os tratamentos de controle das plantas daninhas foram com duas capinas (realizadas aos 20 e 40 dias após a semeadura) e sem capinas. As épocas de amostragem consistiram em coletas da parte aérea e das raízes do milho, realizadas de 15 em 15 dias, até 105 dias após a semeadura (DAS), sendo a primeira amostragem efetuada aos 30 DAS. Utilizou-se o delineamento de blocos completos casualizados, com dez repetições. Nas características avaliadas numa só época, as análises estatísticas foram feitas como um experimento de blocos ao acaso. Quanto às características avaliadas em várias épocas, as análises estatísticas foram feitas em blocos ao acaso com parcelas subdivididas (controle de plantas daninhas nas parcelas). Quatorze espécies de plantas daninhas, que se distribuíram desuniformemente na área experimental, foram as mais importantes. Os crescimentos da parte aérea e do sistema radicular do milho foram 30% menores em parcelas não capinadas do que nas capinadas. A falta de controle das plantas daninhas aumentou a matéria seca da sua parte aérea e reduziu em 23 e 49% os números de espigas verdes comercializáveis, empalhadas e despalhadas, respectivamente. A redução no rendimento de grãos devido à falta de controle das plantas daninhas foi de 38%

Green ear yield and grain yield of maize cultivars in competition with weeds Rendimentos de espigas verdes e de grãos de cultivares de milho em competição com plantas daninhas

The reduction in herbicide use is one of the greatest interests for modern agriculture and several alternatives are being investigated with this objective, including the adoption of cultivars that suppress weeds. The objective of this study was to verify if maize cultivars develop differently, in competition with weeds, to produce green ears and grain. Randomized complete block design was used, with split-plots and five replications. Cultivars DKB 390, DKB 466, DKB 350, AG 7000, AG 7575 and Master, were evaluated in the plots, without weeding and two weedings (at 22 and 41 days after sowing) in sub plots. Twenty-one species were identified in the experimental area, the most frequent being Gramineae (Poaceae), Euphorbiaceae, Leguminosae (Fabaceae) and Convolvulaceae species. There was no difference in the dry biomass above-ground part of the weeds in the plots of the evaluated cultivars. The cultivars behaved similarly in treatments with or without hoeing, except for plant height and ear height evaluations. Without hoeing, plant height increased in cultivar DKB 390, while plant height and ear height decreased in cultivar AG 7575. In the other cultivars, these traits did not change under weed control. The presence of weeds decreased the values of all traits employed to assess green corn yield, with the exception of the total number of green ears and grain yield.<br>A redução do uso de herbicidas é um dos maiores interesses da agricultura moderna e várias alternativas estão sendo investigadas com esse objetivo, dentre elas a adoção de cultivares que suprimam as plantas daninhas. O objetivo do trabalho foi verificar se cultivares de milho, em competição com plantas daninhas, apresentam comportamento diferente para produzir espigas verdes e grãos. Utilizou-se o delineamento de blocos completos casualizados, com parcelas subdivididas, e cinco repetições. As cultivares DKB 390, DKB 466, DKB 350, AG 7000, AG 7575 e Master, semeadas nas parcelas, foram submetidas aos seguintes tratamentos: sem capina e duas capinas (aos 22 e 41 dias após a semeadura). Vinte e uma espécies foram identificadas na área experimental, sendo Gramíneas (Poáceas), Leguminosas (Fabáceas), Euforbiáceas e Convolvuláceas as famílias mais freqüentes. Não houve diferenças na biomassa seca da parte aérea de plantas daninhas nas parcelas das cultivares avaliadas. O comportamento das cultivares foi coincidente nos tratamentos com e sem capina, exceto quando foram avaliadas as alturas da planta e de inserção da espiga. A cultivar DKB teve a altura da planta aumentada e a cultivar AG 7575 teve as Alturas da planta e de inserção da espiga reduzidas, sem a realização das capinas. Nas demais cultivares, essas características não foram alteradas com o controle de plantas daninhas. A presença das plantas daninhas reduziu todas as características utilizadas para avaliação do rendimento de milho verde, à exceção do número total de espigas verdes, e também o rendimento de grãos. As cultivares avaliadas não diferiram quanto ao rendimento de espigas verdes nem quanto ao rendimento de grãos, exceto no peso de espigas despalhadas comercializáveis, em que as cultivares DKB 390 e DKB 350 foram as mais produtivas

Effects of weed "Reestablishment" after hoeing on corn yields Efeitos do "Pegamento" das plantas daninhas, após a capina, sobre os rendimentos do milho

Some growers and researchers sustain the idea that regrowth or root setting of some weeds may occur after hoeing, with detrimental effects over corn. The objective of this study was to evaluate the effects of weed removal from the field, removal after each hoeing, and corn intercropped with gliricidia on weed control and corn yield values. The experimental design consisted of blocks with split-plots and six replicates. Cultivars AG 1051 and BM 2022, planted in the plots, were submitted to the following treatments: no hoeing, two hoeings (at 20 and 40 days after planting), and intercropped with gliricidia. The hoed plots were either submitted to weed removal after the first, second, or both hoeings, or remained without weed removal. In the intercropped treatment, gliricidia was sown by broadcasting at corn planting between the corn rows, at a density of 15 seeds m-2. Twenty-five weed species occurred in the experiment; the most frequent was Digitaria sanguinalis (family Poaceae). The weed control methods tested had similar effects on the cultivars, which were not different from one another with respect to the evaluated traits, except for one-hundred-kernel weight, with cultivar AG 1051 being superior. Weed removal did not influence green corn yield or grain yield. However, the number of kernels/ear was higher in plots where weeds were removed in relation to plots without weed removal, suggesting that weed removal might be beneficial to corn. Besides, a higher dry matter weight was obtained for the above-ground part of weeds removed from the field after the first and second hoeings than the weight of weeds removed after the second hoeing only which, in turn, was higher than the weight of weeds removed after the first hoeing only. Green ear yield, grain yield, and dry matter of the above-ground part of the weeds did not show differences in hoed plots and were superior to the non-weeded plots and the intercropped plots, which were not different from each other; therefore, intercropping with gliricidia did not improve corn yield values.<br>Existe a ideia, entre alguns agricultores e pesquisadores, de que após a realização das capinas à enxada poderia ocorrer o "pegamento" ou rebrota de parte das plantas daninhas, prejudicando o milho. O objetivo do trabalho foi avaliar os efeitos da remoção do campo das plantas daninhas (PD), após cada capina, e da consorciação com gliricídia sobre o controle das PD e sobre os rendimentos do milho. Utilizou-se o delineamento experimental de blocos ao acaso com parcelas subdivididas e seis repetições. As cultivares AG 1051 e BM 2022, plantadas nas parcelas, foram submetidas aos seguintes tratamentos: sem capinas, duas capinas (aos 20 e 40 dias após o plantio) e consorciação com a gliricídia. As parcelas capinadas foram submetidas à remoção das PD, após a primeira, a segunda, ou após ambas as capinas ou sem remoção das PD. Na consorciação, a gliricídia foi semeada a lanço por ocasião da semeadura do milho, entre as fileiras da gramínea, na densidade de 15 sementes m-2. Vinte e cinco espécies de PD ocorreram no experimento, sendo Digitaria sanguinalis, pertencente à família gramineae, a mais frequente. Os métodos de controle das PD tiveram efeitos semelhantes nas cultivares, que não diferiram entre si nas características avaliadas, exceto no peso de cem grãos, com superioridade da cultivar AG 1051. A remoção das PD não influenciou os rendimentos de milho verde e de grãos. Contudo, o número de grãos/espiga foi maior nas parcelas em que as PD foram removidas, do que nas parcelas sem remoção dessas plantas, sugerindo que a remoção das PD pode ser benéfica ao milho. Além disso, um maior peso da matéria seca foi obtido para a parte aérea das plantas daninhas (PMSPAPD) removidas após as duas capinas, em relação ao PMSPAPD removidas apenas após a segunda capina que, por sua vez foi maior que o PMSPAPD removidas após a primeira capina, apenas. Os rendimentos de espigas verdes e de grãos e a matéria seca da parte aérea das PD não diferiram nas parcelas capinadas e foram superiores aos das parcelas não-capinadas ou consorciadas os quais não diferiram entre si; portanto, a consorciação com a gliricídia não melhorou os rendimentos do milho