Hardpan and maize root distribution under conservation and conventional tillage in Agro-Ecological Zone IIA, Zambia

Hardpans (plough/hoe pans) are commonly believed to restrict plant root growth and crop yields under conventional small-scale agriculture in sub-Saharan Africa. This study questions the notion of widespread hardpans in Zambia and their remedy under conservation tillage. Soil penetration resistance was measured in 8x12 grids, covering 80 cm wide and 60 cm deep profiles in 32 soil pits. Large and fine maize roots were counted in 8x6 grids. Soil samples from mid-rows were analysed for pH, exchangeable H+, exchangeable Al3+, cation exchange capacity, total N and extractable P (Bray 1) at six depths from 0-10 to 50-60 cm. Cultivation-induced hardpans were not detected. Soils under conservation tillage were more compact at 5 cm depth than soils under conventional tillage. No differences in root distributions between conservation and conventional tillage were found. Maize ( Zea mays L. ) roots were largely confined to a relatively small soil volume of about 30 cm x 30 cm x 30 cm. Root growth appeared to be restricted by a combination of low concentrations of N and P. Soil acidity and Al saturation appeared to play a minor role in root distribution. L-shaped taproots in soils under manual tillage reported earlier were not necessarily due to hardpans, but may rather be caused by temporarily dry, impenetrable subsoils early in the rain season. There is no scientific basis for the recommendation given to farmers by agricultural extension workers to “break the hardpan” in fields under manual or animal tillage in the study areas.

Chemical changes and heavy metal partitioning in an oxisol cultivated with maize (Zea mays, L.) after 5 years disposal of a domestic and an industrial sewage sludge.

The need for solutions to minimize the negative environmental impacts of anthropogenic activities Fhas increased. Sewage sludge is composed of predominantly organic matter and can be used to improve soil characteristics, such as fertility. Therefore, its application in agriculture is an adequate alternative for its final disposal. However, there is a lack of information on its long-term effects on soil changes in tropical areas. Thus, the objectives of this study were to determine (i) the effect of sewage sludge application on heavy metal build-up in soil and maize grains and leaves, and (ii) the effects of soil amendment with sewage sludge on the chemical properties of a Brazilian oxisol. Besides the increasing levels of Zn, Cu, Ni, and Cr, amending soil with sewage sludge also alters the distribution of these metals by increasing the mobile Phases, which correlated significantly with the increase in metal extraction with two single extractants, Mehlich 1 and DTPA (Diethylene triamine pentaacetic acid). The levels of Fe, Mn, Zn, and Cu in maize grains and leaves increased with the type and rate of sewage sludge application. Nevertheless, metal build-up in soil and plants was within the allowed limits. Significant differences were also found in soil characteristics like humic fractionation with the applied sewage doses. The data obtained does not indicate any expressive drawbacks in the use of sewage sludge as a soil amendment, as the heavy metal concentrations observed are unlikely to cause any environmental or health problems, even overestimated loadings, and are in accordance with the Brazilian regulations on farming land biosolid disposal.

A review of maize-beans and maize-cowpea intercrop systems in the semiarid Northeast Brazil.

Fifty-one experiments on maize -beans and 34 on maize-cowpea intercropping systems conducted mostly in semiarid Northeast Brazil were analysed to get an understanding of the performance of these intercrops in terms of their productivity as well as stability. Both the intercrop systems produced higher yields over their respective sole crops under a wide range of agroclimates; the average advantage with maize-beans was 32%, while that from maize-cowpea was 41%. The optimum row proportion for maize-beans was one maize: three beans, requiring 59% of sole crop maize population and 75% sole bean population. In maize-cowpea, alternate rows or one maize: two cowpea arrangement with about 50% of sole maize density and 100% of sole cowpea population seemed to be optimum. The intercrops failed less frequently compared to sole crops to meet specified incomes or yields. Sorghum seemed to be a good alternative to the traditional cereal because of its improved and consistent performance. Future research needs are discussed for further yield improvement in these two intercrop system.s

Water production function of maize for Northeast Brazil.

Estudou-se atraves de um experimento em blocos ao acaso, os efeitos de quatro niveis de nitrogenio, em diferentes condicoes de umidade, sobre os estagios de crescimento, embonecamento, formacao de graos e prdutividade do milho (Zea mays L.) e as relacoes entre a produtividade e os tres primeiros estagios. Os fatores da resposta de producaobaseados na equacao de Doorenbos e Kassam variaram acentuadamente, nao so com os diferentes estatios de crescimento, mas tambem com diferentes niveis de nitrogenio e os diferentes niveis de agua. Assim, esta equacao nao pareceu ser valida para explicar a resposta de produtividade a niveis de agua. Sugeriu-se um equacao linear modificada. Nesta equacao, a intercessao K1 e inclinacao K2 sao os fatores da resposta de producao. Estes fatores para a cultura do milho foram desenvolvidos para todos os quatro estagios de crescimento e nveis de nitrogenio. Pode-se obter uma eficiencia media do uso de agua, em termos de produtividade, de, aproximadamente, 57,5 kg/ha-cm de agua, sendo, contudo, pequeno o incremento, em face dos niveis crescentes de nitrogenio aplicado ate 120 kg/ha. Os coeficientes de cutura (Kc) calculados estao muito abaixo da estimativa da FAO, para todos os niveis de nitrogenio. Por essa razao, deve haver consideravel economica de agua se estes coeficientes forem usados em lugar da estimativa da FAO. A informacao mostradapode imediatamente ser utilizada para turno de irrigacao e para projetos de irrigacao suplementar planejado para as condicoes doe Nordeste do Brasil.

Resistance of Bt transgenic maize to lesser cornstalk borer (Lepidoptera: Pyralidae).

To determine if Bt maize seedlings are protected against lesser cornstalk borer damage, Bt hybrids at the 3 and 4 leaf stages were tested under temperatures between 20-32oC and artificial infestation. A high level of resistance was reported in all Bt maize as expressed by larval survival, larval weight, damage score, and number of surviving plants. All Bt maize protected plants against lesser cornstalk borer damage. Also, the resistance present in the Bt maize was not affected by daytime temperature.

Life-history traits of Spodoptera frugiperda populations exposed to low-dose Bt maize.

Exposure to Bacillus thuringiensis (Bt) toxins in low- and moderate-dose transgenic crops may induce sublethal effects and increase the rate of Bt resistance evolution, potentially compromising control efficacy against target pests. We tested this hypothesis using the fall armyworm Spodoptera frugiperda, a major polyphagous lepidopteran pest relatively tolerant to Bt notorious for evolving field-relevant resistance to single-gene Bt maize. Late-instar larvae were collected from Bt Cry1Ab and non-Bt maize fields in five locations in Brazil, and their offspring was compared for survival, development, and population growth in rearing environment without and with Cry1Ab throughout larval development. Larval survival on Cry1Ab maize leaves varied from 20 to 80% among the populations. Larvae reared on Cry1Ab maize had seven-day delay in development time in relation to control larvae, and such delay was shorter in offspring of armyworms from Cry1Ab maize. Population growth rates were 50?70% lower for insects continuously exposed to Cry1Ab maize relative to controls, showing the population-level effect of Cry1Ab, which varied among the populations and prior exposure to Cry1Ab maize in the field. In three out of five populations, armyworms derived from Bt maize reared on Cry1Ab maize showed higher larval weight, faster larval development and better reproductive performance than the armyworms derived from non-Bt maize, and one of these populations showed better performance on both Cry1Ab and control diets, indicating no fitness cost of the resistance trait. Altogether, these results indicate that offspring of armyworms that developed on field-grown, single-gene Bt Cry1Ab maize had reduced performance on Cry1Ab maize foliage in two populations studied, but in other three populations, these offspring had better overall performance on the Bt maize foliage than that of the armyworms from non-Bt maize fields, possibly because of Cry1Ab resistance alleles in these populations. Implications of these findings for resistance management of S. frugiperda in Bt crops are discussed.

Assessing the impact of agricultural drought on maize prices in Kenya with the approach of the SPOT-VEGETATION NDVI remote sensing

The high cost of maize in Kenya is basically driven by East African regional commodity demand forces and agricultural drought. The production of maize, which is a common staple food in Kenya, is greatly affected by agricultural drought. However, calculations of drought risk and impact on maize production in Kenya is limited by the scarcity of reliable rainfall data. The objective of this study was to apply a novel hyperspectral remote sensing method to modelling temporal fluctuations of maize production and prices in five markets in Kenya. SPOT-VEGETATION NDVI time series were corrected for seasonal effects by computing the standardized NDVI anomalies. The maize residual price time series was further related to the NDVI seasonal anomalies using a multiple linear regression modelling approach. The result shows a moderately strong positive relationship (0.67) between residual price series and global maize prices. Maize prices were high during drought periods (i.e. negative NDVI anomalies) and low during wet seasons (i.e. positive NDVI anomalies). This study concludes that NDVI is a good index for monitoring the evolution of maize prices and food security emergency planning in Kenya. To obtain a very strong correlation for the relationship between the wholesale maize price and the global maize price, future research could consider adding other price-driving factors into the regression models.

Sensor psychrometric approaches to mitigating aflatoxins in maize dried on farms in Kenya

Kenia liegt in den Äquatorialtropen von Ostafrika und ist als ein weltweiter Hot-Spot für Aflatoxinbelastung insbesondere bei Mais bekannt. Diese toxischen und karzinogenen Verbindungen sind Stoffwechselprodukte von Pilzen und so insbesondere von der Wasseraktivität abhängig. Diese beeinflusst sowohl die Trocknung als auch die Lagerfähigkeit von Nahrungsmitteln und ist somit ein wichtiger Faktor bei der Entwicklung von energieeffizienten und qualitätsorientierten Verarbeitungsprozessen. Die vorliegende Arbeit hat sich zum Ziel gesetzt, die Veränderung der Wasseraktivität während der konvektiven Trocknung von Mais zu untersuchen. Mittels einer Optimierungssoftware (MS Excel Solver) wurde basierend auf sensorerfassten thermo-hygrometrischen Daten der gravimetrische Feuchteverlust von Maiskolben bei 37°C, 43°C und 53°C vorausberechnet. Dieser Bereich stellt den Übergang zwischen Niedrig- und Hochtemperaturtrocknung dar. Die Ergebnisse zeigen deutliche Unterschiede im Verhalten der Körner und der Spindel. Die Trocknung im Bereich von 35°C bis 45°C kombiniert mit hohen Strömungsgeschwindigkeiten (> 1,5 m / s) begünstigte die Trocknung der Körner gegenüber der Spindel und kann daher für eine energieeffiziente Trocknung von Kolben mit hohem Anfangsfeuchtegehalt empfohlen werden. Weitere Untersuchungen wurden zum Verhalten unterschiedlicher Schüttungen bei der bei Mais üblichen Satztrocknung durchgeführt. Entlieschter und gedroschener Mais führte zu einem vergrößerten Luftwiderstand in der Schüttung und sowohl zu einem höheren Energiebedarf als auch zu ungleichmäßigerer Trocknung, was nur durch einen erhöhten technischen Aufwand etwa durch Mischeinrichtungen oder Luftumkehr behoben werden könnte. Aufgrund des geringeren Aufwandes für die Belüftung und die Kontrolle kann für kleine landwirtschaftliche Praxisbetriebe in Kenia daher insbesondere die Trocknung ganzer Kolben in ungestörten Schüttungen empfohlen werden. Weiterhin wurde in der Arbeit die Entfeuchtung mittels eines Trockenmittels (Silikagel) kombiniert mit einer Heizquelle und abgegrenztem Luftvolumen untersucht und der konventionellen Trocknung gegenüber gestellt. Die Ergebnisse zeigten vergleichbare Entfeuchtungsraten während der ersten 5 Stunden der Trocknung. Der jeweilige Luftzustand bei Verwendung von Silikagel wurde insbesondere durch das eingeschlossene Luftvolumen und die Temperatur beeinflusst. Granulierte Trockenmittel sind bei der Maistrocknung unter hygienischen Gesichtspunkten vorteilhaft und können beispielsweise mit einfachen Öfen regeneriert werden, so dass Qualitätsbeeinträchtigungen wie bei Hochtemperatur- oder auch Freilufttrocknung vermieden werden können. Eine hochwertige Maistrocknungstechnik ist sehr kapitalintensiv. Aus der vorliegenden Arbeit kann aber abgeleitet werden, dass einfache Verbesserungen wie eine sensorgestützte Belüftung von Satztrocknern, der Einsatz von Trockenmitteln und eine angepasste Schüttungshöhe praktikable Lösungen für Kleinbauern in Kenia sein können. Hierzu besteht, ggf. auch zum Aspekt der Verwendung regenerativer Energien, weiterer Forschungsbedarf.

Irrigation management with remote sensing: Evaluating irrigation requirement for maize under Mediterranean climate condition

tWater use control methods and water resources planning are of high priority. In irrigated agriculture, theright way to save water is to increase water use efficiency through better management. The present workvalidates procedures and methodologies using remote sensing to determine the water availability in thesoil at each moment, giving the opportunity for the application of the water depth strictly necessaryto optimise crop growth (optimum irrigation timing and irrigation amount). The analysis is applied tothe Irrigation District of Divor, Évora, using 7 experimental plots, which are areas irrigated by centre-pivot systems, cultivated to maize. Data were determined from images of the cultivated surface obtainedby satellite and integrated with atmosphere and crop parameters to calculate biophysical indicatorsand indices of water stress in the vegetation—Normalized Difference Vegetation Index (NDVI), Kc, andKcb. Therefore, evapotranspiration (ETc) was estimated and used to calculate crop water requirement,together with the opportunity and the amount of irrigation water to allocate. Although remote sensingdata available from satellite imagery presented some practical constraints, the study could contribute tothe validation of a new methodology that can be used for irrigation management of a large irrigated area,easier and at lower costs than the traditional FAO recommended crop coefficients method. The remotesensing based methodology can also contribute to significant saves of irrigation water.

Methodology for climate risk assessment of maize intercropped with Brachiaria in the Cerrado of Brazil.

2015

Future climate change impacts on maize production in the Cerrado of Brazil.

2015

Timing expression profile of carotenoids pathway genes in maize grains for characterization of landrace germoplasm from south Brazil.

2011

Population structure of Spodoptera frugiperda collected in maize from different Brazilian geographic regions.

Spodoptera frugiperda é a praga do milho de maior importância econômica no Brasil. Existe pouca informação disponível sobre a estrutura genética, utilizando marcadores SSR, de populações de S. Frugiperda coletadas em cultivos de milho.Neste estudo, 21 marcadores SSR foram utilizados para avaliar a diversidade e a estrutura genética de S. frugiperda coletadas em regiões brasileiras geograficamente distintas. Um total de 227 alelos foram obtidos, com uma média de 10,76 alelos por marcador, e os valores do Conteúdo de Informação Polimórfica (PIC) variaram de 0,242 a 0,933, com uma média de 0,621, indicando alto poder de discriminação. O FST geral, 0,061, indicou moderada diferenciação genética entre as populações de S. frugiperda coletadas em milho e a Amova mostrou que 87,36% da variação está dentro de populações. O teste de Mantel mostrou correlação significativa entre distâncias genéticas e distâncias geográficas. Os dados genéticos demonstraram que todos os indivíduos dos seis locais de amostragem foram estruturados em duas sub-populações, sendo uma delas composta apenas pela população CL, coletada no estado do Rio Grande do Sul. O conhecimento sobre a diversidade genética e a estrutura populacional de S. frugiperda é importante para o desenvolvimento de estratégias para os sistemas de manejo e monitoramento de insetos-praga, especialmente para a diferenciada população CL.

Parametrização e avaliação do modelo CSM-Ceres-Maize para cultivares de milho recomendadas para a microrregião de Pelotas, RS.

Os objetivos deste trabalho foram parametrizar o modelo CSM-CERES-Maize para diferentes cultivares e avaliar o desempenho das simulações do modelo. Para a parametrização do modelo, foi conduzido ensaio irrigado, na estação experimental da Embrapa Clima Temperado, localizada no município de Pelotas, RS, onde foram utilizadas as cultivares Amarelão, AL 30, AG 5011 e AG 122. Um segundo ensaio, em regime de sequeiro, com as cultivares Amarelão e AL 30, foi conduzido para se avaliar a capacidade preditiva do modelo em Canguçu, RS. A qualidade das simulações foi avaliada estatisticamente empregando-se o índice ?d? de concordância e o quadrado médio do erro, RMSE. Valores de RMSE e de ?d? indicaram simulações de boa qualidade e adequado índice de concordância para a simulação da produtividade de grãos nos ensaios de parametrização e avaliação do modelo. Os melhores valores de RMSE e de ?d? para a fitomassa seca da parte aérea foram observados para a cultivar AG 5011 no ensaio de parametrização e para a variedade AL 30 no ensaio de avaliação do modelo. Nos ensaios, para todas as cultivares, as simulações do número de folhas foram consideradas excelentes.

Microbial activities in soils cultivated with transgenic maize expressing Bacillus thuringiensis Cry1 Ab and Cry1 F genes.

A área brasileira plantada com milho geneticamente modificado (GM) expressando genes Cry derivados da bactéria do solo Bacillus thuringiensis (Bt) aumentou de 4,9% (5,0 milhões de hectares) da área total plantada em 2009 para 81,4% (15,83 milhões de hectares) em 2014. No entanto, estudos sobre os efeitos da tecnologia Bt-milho sobre microrganismos não alvo em solos tropicais são incipientes. Dessa forma, foi realizado experimento de campo para avaliar a atividade fisiológica das comunidades bacterianas associadas com genótipos de milho Bt plantados em Latossolo Vermelho Escuro do Cerrado e solos hidromórficos da planície com inundações localizadas. Um híbrido não transgênico (30F35) e seus homólogos transgênicos 30F35Y (Cry1Ab) e 30F35H (Cry1F) foram plantados com delineamento de blocos casualizados com quatro repetições. Solos rizosféricos e não rizosféricos coletados de plantas no estádio de florescimento foram submetidos aos ensaios de diversidade metabólica com Biolog e atividades enzimáticas de urease, arginase, fosfatase ácida e fosfatase alcalina. Solos rizosféricos apresentaram maior atividade microbiana e não foram detectadas diferenças significativas entre os genótipos em todos os parâmetros bioquímicos e de solo avaliados. Os resultados sugerem que o milho Bt não afeta negativamente a comunidade microbiana dos solos tropicais.