Effect of Combined Cattle Manure and Mineral Nitrogen on Maize N Uptake and Grain Yield

The effectiveness in increasing N recovery by maize ( Zea mays L.) of N fertiliser (0, 60, 120 kg N ha-1 annum-1) and aerobically composted cattle manure (0, 12.5 Mg ha-1 annum-1 or 37.5 Mg ha-1 applied only in the first year) was determined when the two N sources were applied separately or in combination. A field experiment was established on a moderately leached sandy loam soil (Typic Kandiustalf) over three seasons, and N uptake was determined fortnightly from 4 weeks after planting (WAP) until harvest. Net N recovery during plant growth increased with N application rate (up to 90 kg N ha-1 in first season and up to 60 kg N ha-1 in second and third seasons). Net N recovery from manure during the growing period was relatively poor. There was no net recovery (up to 12 WAP) from annual application of manure during the first season and from first year application of the large rate of manure in the second season. Combined application of manure and N fertiliser increased net N recovery in all growing seasons (up to 120 kg N ha-1) above that achieved by separate applications of both N sources. There was a manure by N fertiliser interaction that enhanced N recovery, in two treatment combinations during the first season (low manure rate) and in the second season, and this was attributed to some non-N nutrient effects of the manure. Highest percentage increases in total N recovery at harvesting were observed when manure was combined with the low N fertiliser rate (60 kg N ha-1) (av. 58% in first season, 63% in third season) and limited further increases were recorded when the N fertiliser rate was doubled (120 kg N ha-1) (av. 15% in first season, 32% in third season). It was concluded that aerobically composted cattle manure from the smallholder farming areas of Zimbabwe was a poor source of N for maize growth in the short-term, even at high application rates. Combined application of manure with judicious use of N fertiliser can be positively exploited by smallholder farmers in Zimbabwe and other countries of sub-Saharan Africa, to increase yields through enhanced efficiency of use of scarce nutrient resources.L'efficacité dans l'augmentation de N du rétablissement du ma¿s ( Zea mays L.) de fertilisant N (0, 60, 120 kg N ha-1 annum-1) et le fumier de vache aérobicallement composté (0, 12,5 Mg ha-1 appliqué seulement en première année) était déterminée quand les deux sources de N étaient appliquées séparément ou en combinaison. Une expérience sur le terrain était établie sur un filtre de terre de sol sable (Typic Kandiustalf) au delà de trois saisons, et la consommation de N était déterminée bimensuellement á partir de quatre semaines après la plantation (WAP) jusqu'à la récolte. Le rétablissement net de N pendant la croissance de la plante a augmenté avec le taux d'application de N (jusqu'à 90 kg N ha-1 en première saison et jusqu'à 60 kg N ha-1 en seconde et troisième saisons). Le rétablissement net de N á partir du fumier durant la période de croissance était relativement pauvre. Il n'y avait pas rétablissement (jusqu'à 12 WAP)á partir de l'application annuelle durant la première saison et á partir de la première année d'application du large taux de fumier dans la seconde saison. L'application combinée du fumier et du fertilisant N a augmenté le rétablissement net dans toutes les saisons de croissance (jusqu'à 120 kg N ha-1) au delà de celui accomplit par les applications séparées de deux sources de N. Il y avait un fumier par l'interaction du fertilisant N qui a amélioré le rétablissement de N, dans deux combinaisons de traitement pendant la première saison (faible taux de fumier) et dans la seconde saison, et ceci était attribué aux non effets des substances N du fumier. Les augmentations élevées du pourcentage dans le rétablissement total de N á la récolte étaient observées quand le fumier était combiné avec le faible taux de fertilisant N (60 kg N ha-1) (av. 58% en première saison, 63% en troisième saison) et davantage augmentations étaient enregistrées quand le taux de fertilisant était doublé (120 kg N ha-1) (av. 15% en première saison, 32% en troisième saison). Il était conclu que le fumier de vache aérobicallement composté des fermiers des petites surfaces du Zimbabwe était une pauvre source de N pour la croissance de ma¿s à court terme, même aux taux d'application élevés. L'application combinée du fumier avec un usage judicieux du fertilisant N peut être positivement exploitée par les petits fermiers au Zimbabwe et autres pays de l'Afrique sub-Saharienne, pour augmenter les rendements à travers l'efficacité améliorée de l'usage des rares ressources des substances

Effect of combined cattle manure and mineral nitrogen on maize N uptake and grain yield

The effectiveness in increasing N recovery by maize (Zea mays L.) of N fertiliser (0, 60, 120 kg N ha-1 annum-1) and aerobically composted cattle manure (0, 12.5 Mg ha-1 annum-1 or 37.5 Mg ha-1 applied only in the first year) was determined when the two N sources were applied separately or in combination. A field experiment was established on a moderately leached sandy loam soil (Typic Kandiustalf) over three seasons, and N uptake was determined fortnightly from 4 weeks after planting (WAP) until harvest. Net N recovery during plant growth increased with N application rate (up to 90 kg N ha-1 in first season and up to 60 kg N ha-1 in second and third seasons). Net N recovery from manure during the growing period was relatively poor. There was no net recovery (up to 12 WAP) from annual application of manure during the first season and from first year application of the large rate of manure in the second season. Combined application of manure and N fertiliser increased net N recovery in all growing seasons (up to 120 kg N ha-1) above that achieved by separate applications of both N sources. There was a manure by N fertiliser interaction that enhanced N recovery, in two treatment combinations during the first season (low manure rate) and in the second season, and this was attributed to some non-N nutrient effects of the manure. Highest percentage increases in total N recovery at harvesting were observed when manure was combined with the low N fertiliser rate (60 kg N ha-1) (av. 58% in first season, 63% in third season) and limited further increases were recorded when the N fertiliser rate was doubled (120 kg N ha-1) (av. 15% in first season, 32% in third season). It was concluded that aerobically composted cattle manure from the smallholder farming areas of Zimbabwe was a poor source of N for maize growth in the short-term, even at high application rates. Combined application of manure with judicious use of N fertiliser can be positively exploited by smallholder farmers in Zimbabwe and other countries of sub-Saharan Africa, to increase yields through enhanced efficiency of use of scarce nutrient resources

Fertilizer Use Efficiency and Nitrate Leaching in a Tropical Sandy Soil

Maize (Zea mays L.) production in the smallholder farming areas of Zimbabwe is based on both organic and mineral nutrient sources. A study was conducted to determine the effect of composted cattle manure, mineral N fertilizer, and their combinations on NO3 concentrations in leachate leaving the root zone and to establish N fertilization rates that minimize leaching. Maize was grown for three seasons (1996-1997, 1997-1998, and 1998-1999) in field lysimeters repacked with a coarse-grained sandy soil (Typic Kandiustalf). Leachate volumes ranged from 480 to 509 mm yr-1 (1395 mm rainfall) in 1996-1997, 296 to 335 mm yr-1 (840 mm rainfall) in 1997-1998, and 606 to 635 mm yr-1 (1387 mm rainfall) in 1998-1999. Mineral N fertilizer, especially the high rate (120 kg N ha-1), and manure plus mineral N fertilizer combinations resulted in high NO3 leachate concentrations (up to 34 mg N L-1) and NO3 losses (up to 56 kg N ha-1 yr-1) in 1996-1997, which represent both environmental and economic concerns. Although the leaching losses were relatively small in the other seasons, they are still of great significance in African smallholder farming where fertilizer is unaffordable for most farmers. Nitrate leaching from sole manure treatments was relatively low (average of less than 20 kg N ha-1 yr-1), whereas the crop uptake efficiency of mineral N fertilizer was enhanced by up to 26% when manure and mineral N fertilizer were applied in combination. The low manure (12.5 Mg ha-1) plus 60 kg N ha-1 fertilizer treatment was best in terms of maintaining dry matter yield and minimizing N leaching losses

Effects of high temperature on survival, symbiotic performance and genomic modifications of bean nodulating Rhizobium strains Sobrevivência, fixação de nitrogênio e modificações genéticas em estirpes de Rhizobium sp. efetivas na nodulação do feijoeiro, expostas à altas temperaturas

High temperatures can affect the survival, establishment and symbiotic properties of Rhizobium strains. Bean nodulating Rhizobium strains are considered particularly sensitive because on this strains genetic recombinations and/or deletions occur frequently, thus compromising the use of these bacteria as inoculants. In this study R. tropici and R. leguminosarum bv. phaseoli strains isolated from Cerrado soils were exposed to thermal stress and the strains’ growth, survival and symbiotic relationships as well as alterations in their genotypic and phenotypic characteristics were analyzed. After successive thermal shocks at 45ºC for four hours, survival capacity appeared to be strain-specific, independent of thermo-tolerance and was more apparent in R. tropici strains. Certain R. leguminosarum bv. phaseoli strains had significant alterations in plant dry weight and DNA patterns obtained by AP-PCR method. R. tropici strains (with the exception of FJ2.21) were more stable than R. leguminosarum bv. phaseoli strains because no significant phenotypic alterations were observed following thermal treatments and they maintained their original genotypic pattern after inoculation in plants.<br>Altas temperaturas podem afetar a sobrevivência, estabelecimento e as propriedades simbióticas em estirpes de Rhizobium. As estirpes capazes de nodular o feijoeiro têm sido consideradas particularmente sensíveis, porque nessas estirpes é comum a ocorrência de recombinações e/ou deleções genômicas comprometendo, muitas vezes, a sua utilização como inoculantes. Neste trabalho, procurou-se avaliar a capacidade de crescimento e sobrevivência em temperaturas elevadas de estirpes de Rhizobium efetivas na fixação de nitrogênio no feijoeiro isoladas dos cerrados, bem como avaliar suas características fenotípicas e genotípicas após choque térmico. A capacidade de sobrevivência à temperaturas elevadas, avaliada após choques térmicos sucessivos (45ºC por 4 horas) mostrou ser uma característica própria de cada estirpe, independente de sua termotolerância, que aparentemente foi mais acentuada nas estirpes de R. tropici. Algumas estirpes de R. leguminosarum bv. phaseoli mostraram alterações significativas (Duncan 5% de probabilidade) nas suas características fenotípicas (produção de matéria seca) após choques térmicos e nos seus padrões genômicos evidenciados pela técnica de AP-PCR. As estirpes de R. tropici foram aparentemente mais estáveis não sendo detectadas alterações fenotípicas significativas e com exceção da estirpe FJ2.21, após choque térmico e inoculação na planta hospedeira, mantiveram o padrão genômico original