• Authors:
    • Pereira, M.
    • Torres, J.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 32
  • Issue: 4
  • Year: 2008
  • Summary: A study with eight cover crops types was developed: pearl millet ( Pennisetum americanum [ Pennisetum glaucum] syn. tiphoydes), brachiaria grass ( Brachiaria brizantha [ Urochloa brizantha]), sorghum ( Sorghum bicolor), pigeonpea ( Cajanus cajan), sunn hemp ( Crotalarea juncea) and black oat ( Avena strigosa [ Avena nuda]), fallow land and conventional culture (control) in the experimental area of CEFET-Uberaba-MG, in a cerrado area to evaluate K accumulation and release. The dry mass production, crop residue decomposition in litter bags and K release were evaluated. A mathematical model was used to describe residue decomposition and K release, which calculates the decomposition constant (k) and half-time life. Pearl millet, sorghum and the sunn hemp were the cover crops that produced most dry matter while K accumulation was highest in the grasses. K release was highest in pearl millet, oats, brachiaria grass and sunn hemp in the first 42 days after handling. Brachiaria grass had the shortest half-time life and the highest K release rate.
  • Authors:
    • Fabian, A.
    • Pereira, M.
    • Torres, J.
  • Source: PESQUISA AGROPECUARIA BRASILEIRA
  • Volume: 43
  • Issue: 3
  • Year: 2008
  • Summary: This study investigated dry biomass production, decomposition rate and macronutrients release (N, P, Ca, Mg and S) of cover crops cultural residues, in a no-till savanna soil in Minas Gerais, Brazil. The cover crops tested were: pearl millet ( Pennisetum americanum syn. typhoides), brachiaria grass ( Brachiaria brizantha [Urochloa brizantha] cv. Marandu), sorghum ( Sorghum bicolor), pigeon pea ( Cajanus cajan), sunn hemp ( Crotalaria juncea) and black oat ( Avena nuda), compared to a fallow plot (control). The experiment was carried out in an Oxisol, medium texture. A randomized block design, in a split-plot array in time, with four replications, was used. Dry biomass production was evaluated 110 days after sowing. Decomposition rate was evaluated by litter bags containing cultural residues. Millet and sunn hemp were the cover crops (grass and legume) with the highest dry biomass production and N accumulation, in the two evaluation periods. The highest decomposition rate and nutrient release occurred at 42 days after desiccation. The highest values of half life were observed in dry period.
  • Authors:
    • Baigent, R.
    • Kelly, K. B.
    • Phillips, F. A.
  • Source: Australian Journal of Experimental Agriculture
  • Volume: 48
  • Year: 2008
  • Authors:
    • Kelly, K.
    • Armstrong, R.
    • Phillips, F.
    • Officer, S. J.
  • Source: 14th Australian Agronomy Conference
  • Year: 2008
  • Authors:
    • Aarndt, S. K.
    • Eckard, R.
    • Livesley, S. J.
  • Source: Plant and Soil
  • Volume: 309
  • Issue: 1-2
  • Year: 2008
  • Authors:
    • Graham, J.
    • Kelly, K.
    • Li, Y.
    • Chen, D.
    • Edis, R.
    • Turner, D. A.
  • Source: The 2008 Joint Annual Meeting
  • Year: 2008
  • Authors:
    • Eckard, R.
    • Barker-Reid, F.
    • Chen, D.
    • Li, Y.
  • Source: Plant and Soil
  • Volume: 309
  • Issue: 1-2
  • Year: 2008
  • Authors:
    • Lopez, M. V.
    • Cantero-Martinez, C.
    • Arrue, J. L.
    • Alvaro-Fuentes, J.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 2
  • Year: 2008
  • Summary: Under semiarid conditions, soil quality and productivity can be improved by enhancing soil organic matter content by means of alternative management practices. In this study, we evaluated the feasibility of no-till (NT) and cropping intensification as alternative soil practices to increase soil organic C (SOC). At the same time, we studied the influence of these management practices on two SOC fractions (particulate organic matter C, POM-C, and the mineral-associated C, Min-C), in semiarid agroecosystems of the Ebro River valley. Soil samples were collected from five soil layers (0–5-, 5–10-, 10–20-, 20–30-, 30–40-cm depth) during July 2005 at three long-term tillage experiments located at different sites in the Ebro River valley (northeast Spain). Soil bulk density, SOC concentration and content, SOC stratification ratio, POM-C, and Min-C were measured. Higher soil bulk density was observed under NT than under reduced tillage (RT), subsoil tillage (ST), or conventional tillage (CT). At the soil surface (0–5-cm depth), the highest total SOC concentration, POM-C, and Min-C were measured under NT, followed by RT, ST, and CT, respectively. In the whole soil profile (0–40 cm), similarly, slightly greater SOC content was measured under NT than under CT with the exception of the Selvanera site, where deep subsoil tillage combined with moldboard plowing accumulated more SOC than NT. In semiarid Mediterranean agroecosystems where CT consists in moldboard plowing, NT is a viable management practice to increase SOC.
  • Authors:
    • Place, F.
    • Ajayi, O. C.
    • Akinnifesi, F. K.
    • Sileshi, G.
  • Source: Plant and Soil
  • Volume: 307
  • Issue: 1-2
  • Year: 2008
  • Summary: A number of studies have tested the effect of woody and herbaceous legumes on soil fertility and maize yields in sub-Saharan Africa. However, their effects on maize productivity are much debated because results have been variable. A meta-analysis was conducted with the aim of evaluating the evidence in support of yield benefits from woody and herbaceous green manure legumes. A total of 94 peer-reviewed publications from West, East and southern Africa qualified for inclusion in the analysis. Maize yield from herbaceous green manure legumes (54 publications), non-coppicing legumes (48 publications), coppicing woody legumes (10 publications), natural fallows (29 publications), and fully fertilized monoculture maize (52 publications) were compared. Mixed linear modelling using yield differences (D) and response ratios (RR) indicated that the response to legumes is positive. The mean yield increase (D) over unfertilized maize was highest (2.3 t ha-1) and least variable (CV=70%) in fully fertilized maize, while it was lowest (0.3 t ha-1) and most variable (CV=229%) in natural fallows. The increase in yield over unfertilized maize was 1.6 t ha-1 with coppicing woody legumes, 1.3 t ha-1 with non-coppicing woody legumes and 0.8 t ha-1 with herbaceous green manure legumes. Doubling and tripling of yields relative to the control (RR > 2) was recorded in coppicing species (67% of the cases), non-coppicing legumes (45% of the cases), herbaceous green manure legumes (16% of the cases) and natural fallows (19% of the cases). However, doubling or tripling of yields occurred only in low and medium potential sites. Amending post-fallow plots with 50% of the recommended fertilizer dose further increased yields by over 25% indicating that legume rotations may play an important role in reducing fertilizer requirements. Except with the natural fallow, the 95% confidence intervals of D and RR were higher than 1 and 0, respectively indicating significant and positive response to treatments. Therefore, it is concluded that the global maize yield response to legumes is significantly positive and higher than unfertilized maize and natural vegetation fallows.
  • Authors:
    • Hedderley, D. I.
    • Barlow, H. E.
    • Francis, G. S.
    • Beare, M. H.
    • Thomas, S. M.
  • Source: Plant and Soil
  • Volume: 309
  • Issue: 1
  • Year: 2008
  • Summary: Nitrous oxide (N2O) emissions to the atmosphere from grazed pasture can be high, especially from urine-affected areas. When pastoral soils are damaged by animal treading, N2O emissions may increase. In New Zealand, autumn-sown winter forage crops are often grown as a break-crop prior to re-sowing pasture. When these crops are grazed in situ over winter (as is common in New Zealand) there is high risk of soil damage from animal treading as soil moisture contents are often high at this time of year. Moreover, the risk of soil damage during grazing increases when intensive tillage practices are used to establish these forage crops. Consequently, winter grazed forage crops may be an important source of N2O emissions from intensive pastoral farming systems, and these emissions may be affected by the type of tillage used to establish them. We conducted a replicated field experiment to measure the effects of simulated cattle grazing (mowing followed by simulated treading and the application of synthetic urine) at three soil moisture contents ( field capacity) on measured N2O emissions from soil under an autumn (March) sown winter forage crop (triticale) established with three levels of tillage intensity: (a) intensive, IT, (b) minimum, MT, or (c) no tillage, NT. In all treatments, bulk density in the top 7.5 cm of the soil was unaffected by treading when simulated grazing occurred at field capacity, and by 10% in the MT plots trodden at > field capacity. Treading did not significantly increase the bulk density in the NT plots. Emissions of N2O from the tillage treatments decreased in the order IT > MT > NT. N2O emissions were greatest from plots that were trodden at > field capacity and least from plots trodden at field capacity. The N2O emission from urine-amended NT plots that were trodden at < field capacity was 2.0 kg ha(-1) over 90 days (0.25% of the total urine N applied). Decreasing the intensity of tillage used to establish crops and restricting grazing when soils are wet are two of the most effective ways to minimise the risk of high N2O emissions from grazed winter forage crops.