• Authors:
    • Djigal, D.
    • Saj, S.
    • Rabary, B.
    • Blanchart, E.
    • Villenave, C.
  • Source: Soil & Tillage Research
  • Volume: 118
  • Year: 2012
  • Summary: Conservation agriculture (CA) is rapidly developing in Madagascar but little is known about its effects on local soil functioning. To assess some of those effects, we investigated the effects of three CA systems and two levels of fertilization on soil functioning using nematofauna as indicator. The systems consisted in (i) soybean (Glycine max L.)-maize (Zea mays L) rotation with mulch of residues, CA-R; (ii) bean (Phaseolus vulgaris L.)-soybean rotation with living mulch of Pennisetum clandestinum, CA-K; (iii) continuous maize with living mulch of Desmodium uncinatum, CA-D and were compared with soybean-maize under conventional tillage (CT) and natural fallow (NF). The fertilization levels consisted in ( i) farmyard manure, FYM; and (ii) farmyard manure + mineral fertilizers, FYM + NPK. Located in the Highlands of Madagascar, the experiment was setup in 1991 and andic Dystrustept soil had been sampled in 2005-2007. We measured nematode abundances and ecological indices as well as the abundance and biomass of soil macrofauna, soil water and organic C and N contents and plant yields. We hypothesized that (1) CA including maize in monoculture would lead to higher abundance of plant-parasitic nematodes; (2) both dead-residue mulch and inorganic fertilization would lead to a more basal nematode community structure; and (3) that the combination of system effects on soil nematode community would be able to forecast differential crop yields for the CA systems. Our results show that CA systems tested were able to support better/comparable maize and soybean yields compared with CT, provided that crop rotation is correctly managed. Supporting our first hypothesis, abundance of plant parasitic nematodes was (40-150 times) higher under maize monoculture. Abundance of soil nematofauna and trophic groups (excepted carnivores and omnivores) was stable during the three years. Inorganic fertilization increases carnivorous and omnivorous nematodes to 122% and 140%, respectively. Ecological indices showed that soil functioning of CA systems was intermediate between that NF and CT. CA systems were characterized by a highly structured soil food-web compared with CT. Yet, soil processes intensity revealed to be lower in CA with dead mulch compared with CA with living mulch, contrasting with our second hypothesis. The characterization of nematofauna discriminated well the different systems and supports our third hypothesis. Nematode structure and enrichment indices were significantly correlated to soil organic C and N content as well as grain yields. They proved to be powerful bio-indicators of soil functioning in the CA systems studied.
  • Authors:
    • Hussein, M. S.
    • Elsebai, M. N.
    • Rihan, M. K.
  • Source: Arab Universities Journal of Agricultural Sciences
  • Volume: 20
  • Issue: 1
  • Year: 2012
  • Summary: Egypt depends on the Nile River as a major source of water, it provides about 76.3% of its water requirements, other water sources provides about 23.7% of total water requirements. Agriculture sector is the main consumer of water in Egypt as it consumed about 85.9% of the total actual consumption of water in 2009. The main problem of the present paper is the decrease in the efficiency of water use in Egyptian agriculture. The objective of paper is to assess the efficiency of water use in agriculture in the old and new land Egypt through the use of partial efficiency measures. Results showed that in average of the cost of irrigation per feddan during the period (1998-2009), that was for winter crops in the old lands as follows: 85.3, 105.8, 119.3, 127.3 pounds/feddan for faba bean, sugar beet, alfalfa sustained, wheat at a cost of irrigation per feddan of which respectively. For summer crops in old land cost was about 114.7, 129.5, 139.8, 156.2, 217.8, 606.1 pounds/feddan at a cost of, sesame, soybean, peanut, corn, rice, sugar cane, respectively. For the winter crops in the new lands irrigation cost per feddan was about L.E 99.3, 169.0 for garlic and onion respectively. Summer crops in the new lands irrigation costs for watermelon, cucumber, potatoes, eggplant, peppers, and tomatoes were as follows: L.E 92.4, 133, 138.7, 139.8, 157.7, 194.3 pounds/feddan respectively. The results of the statistical analysis of partial-efficiency measures showed that, according to the criterion of net revenue from the water unit - winter crops on the old land as follows: alfalfa, wheat, faba bean, and sugar beet. As for the summer crops of old land the results showed of the statistical estimate of the partial-efficiency measures that peanuts, corn, sesame, sugar cane, rice, soybeans respectively. In the new lands the results of statistical analysis for the partial-efficiency measures, according to the standard net return of the water unit for winter crops were garlic followed by the first crop of onions. As for the summer crops, the results of statistical analysis of partial-efficiency measures, according to the standard net return of the water unit came summer crops in the new lands, were as follows: potatoes, tomatoes, watermelon, cucumber, eggplant, pepper. The results in general indicated the necessaries of reconsidering the present structure of cropping pattern to increase the efficiency of irrigation water use.
  • Authors:
    • Albuquerque, J.
    • Picolla, C.
    • Mafra, A.
    • Andrade, A.
    • Bertol, I.
  • Source: Ciencia Rural
  • Volume: 42
  • Issue: 5
  • Year: 2012
  • Summary: Suitable soil management is one of the bases for sustainability in agricultural systems. The study aimed to evaluate chemical properties of a Humic Dystrudept for 12 years under two tillage systems, with crops rotation and succession. The experiment was carried out in Lages, SC, under conventional tillage (CT) and no-till (NT), with rotation (r) and succession (s) cropping systems, using crop sequences of beans-fallow-maize-fallow-soybean in CTr; maize-fallow in CTs; beans-oats-maize-fodder radish-soybean-vetch in NTr; and maize-vetch in NTs. The experimental design was completely randomized with four replicates. The soil samples were collected in the layers 0-2.5, 2.5-5, 5-10 and 10-20 cm. The variables assessed were total organic carbon (TOC), calcium, magnesium, exchangeable aluminum, phosphorus, potassium, total nitrogen (TN) and water pH. The no-tillage system increased TOC and nutrient levels in comparison with conventional tillage, especially in the surface soil layer. Maize and vetch crop succession had higher TOC and TN contents in the surface soil layer compared to crop rotation under no-tillage.
  • Authors:
    • Matos, M.
    • Machineski, O.
    • Balota, E.
  • Source: REVISTA BRASILEIRA DE ENGENHARIA AGRICOLA E AMBIENTAL
  • Volume: 16
  • Issue: 5
  • Year: 2012
  • Summary: The objective of this work was to evaluate the changes in microbial biomass C, N and P due to the application of pig slurry under different soil tillage systems. The experiment was established in a clayey Oxisol, Eutrophic Red Latossol in Palotina, PR. Different quantities of pig slurry (0, 30, 60 and 120 m 3 ha -1 year -1) were applied to the soil prior to the summer and winter crop season under conventional tillage (CT) and no tillage (NT), in three replicates. The area was cultivated with soybean ( Glycine max L.) or maize ( Zea mays L.) in the summer and wheat ( Triticum sativum Lam.) or oat ( Avena sativa L.) in the winter. The soil samples were collected in March and October of 1998 and 1999 at depths of 0-5, 5-10 and 10-20 cm. The soil tillage and pig slurry application influenced the microbial biomass C, N and P. The microbial biomass and the microbial activity presented high sensibility to detect changes in the soil due to tillage and the application of pig slurry. The soil microbial biomass and C mic/C org relation increased as the quantity of applied pig slurry increased. The metabolic quotient under CT increased with depth while under NT it decreased. The soil microbial biomass was enriched in N and P under NT and as the quantity of applied pig slurry increased.
  • Authors:
    • Schlegel, A.
    • Halvorson, A.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 5
  • Year: 2012
  • Summary: Limited irrigation management practices are being used in the Central Great Plains to conserve water by optimizing crop water use efficiency. Limited irrigation may reduce total crop biomass production and amount of crop residue returned to the soil. Crop residue production within four no-till (NT) crop rotations [continuous corn ( Zea mays L.) (CC); corn-winter wheat ( Triticum aestivum L.) (CW); corn-winter wheat-grain sorghum ( Sorghum bicolor L. Moench) (CWS); corn-winter wheat-grain sorghum-soybean [ Glycine max (L.) Merr.] (CWSSb)] was measured and changes in soil organic carbon (SOC) and total soil nitrogen (TSN) stocks were monitored for 10 yr. Crop residue yields varied with crop being produced and with rotation, as did residue N and C returned to the soil. The C/N ratio of the residue varied with crop. The SOC and TSN pools increased with time in all rotations. The rate of gain in SOC and TSN mass for each rotation was 717, 477, 335, and 270 kg SOC ha -1 yr -1 and 114, 92, 87, and 84 kg TSN ha -1 yr -1 for the CC, CW, CWS, and CWSSb rotations, respectively, in the 0- to 30.5-cm soil depth. The rate of change in SOC and TSN mass was lowest with CWSSb (8.7 Mg residue ha -1 yr -1) and highest with CC (12.0 Mg residue ha -1 yr -1). Approximately 6.8 to 7.6 Mg residue ha -1 yr -1 would be needed to maintain SOC stocks under limited irrigation.
  • Authors:
    • Neumann, M.
    • Lacerda, M.
    • Lago, W.
  • Source: REVISTA BRASILEIRA DE ENGENHARIA AGRICOLA E AMBIENTAL
  • Volume: 16
  • Issue: 7
  • Year: 2012
  • Summary: The intensively increasing agricultural use of Distrito Federal soils may compromise their quality and trigger environmental problems in the region. Given this fact, the objective of this work was to study the soil quality (SQ) indicators, in areas under no tillage (PD), with diversified managements (corn-soybean rotation and bean-sorghum succession), at the Riberao Extrema watershed, Distrito Federal. Soil bulk density (Ds), flocculation index (GF), organic matter (MO), cation exchange capacity (CTC), microbial respiration (Rmic) and microbial biomass carbon (Cmic) were the attributes of SQ evaluated. Statistical analysis was performed using the statistical software Statistics Analysis System (SAS) and consisted of analysis of variance (ANOVA) followed by Tukey test for comparison of means. Results show that some of the evaluated SQ indicators were affected by different types of soil management under evaluation (Ds, Cmic and MO), while others were not sensitive to them (GF, CTC and Rmic). Positive correlation was found between MO and CTC of the soils in both investigated treatments, highlighting the importance of no tillage system on the chemical properties of soil.
  • Authors:
    • Gaihre, Y. K.
    • Pokharel, B. B.
    • Suyama, K.
    • Itoh, K.
    • Kaneto, M.
    • Adhikari, D.
  • Source: PLANT AND SOIL
  • Volume: 357
  • Issue: 1-2
  • Year: 2012
  • Summary: This study was conducted to reveal the genetic diversity of soybean-nodulating rhizobia in Nepal in relation to climate and soil properties. A total of 102 bradyrhizobial strains were isolated from the root nodules of soybeans cultivated in 12 locations in Nepal varying in climate and soil properties, and their genetic diversity was examined based on 16S rDNA, ITS regions of 16S-23S rDNA, nodC and nifH. In vitro growth properties of some representative strains were examined to elucidate their characteristic distribution in Nepal. Four species of the genus Bradyrhizobium were isolated, and B. japonicum dominated at temperate locations, while in subtropical locations, B. elkanii, B. yuanmingense, and B. liaoningense dominated at acidic, moderately acidic, and slightly alkaline soils, respectively. The relative nodule occupancies could not be fully explained by their in vitro growth properties. Similar nodC and nifH genes among the strains suggested co-evolution of these genes also in Nepal, probably through horizontal gene transfer. The influence of climate and soil pH on diversity at the sub-species level was revealed. It is concluded that the highly diverse climate and soils in Nepal might be conducive for the existence of diverse soybean rhizobial strains.
  • Authors:
    • Crosson, E.
    • Bandaru, V.
    • West, T.
    • Andrews, A.
    • Lauvaux, T.
    • Davis, K.
    • Richardson, S.
    • Miles, N.
  • Source: Journal of Geophysical Research-Biogeosciences
  • Volume: 117
  • Issue: G1
  • Year: 2012
  • Summary: This study presents observations of atmospheric boundary layer CO2 mole fraction from a nine-tower regional network deployed during the North American Carbon Program's Mid-Continent Intensive (MCI) during 2007-2009. The MCI region is largely agricultural, with well-documented carbon exchange available via agricultural inventories. By combining vegetation maps and tower footprints, we show the fractional influence of corn, soy, grass, and forest biomes varies widely across the MCI. Differences in the magnitude of CO2 flux from each of these biomes lead to large spatial gradients in the monthly averaged CO2 mole fraction observed in the MCI. In other words, the monthly averaged gradients are tied to regional patterns in net ecosystem exchange (NEE). The daily scale gradients are more weakly connected to regional NEE, instead being governed by local weather and large-scale weather patterns. With this network of tower-based mole fraction measurements, we detect climate-driven interannual changes in crop growth that are confirmed by satellite and inventory methods. These observations show that regional-scale CO2 mole fraction networks yield large, coherent signals governed largely by regional sources and sinks of CO2.
  • Authors:
    • Bernhardt, E.
    • Ardon, M.
    • Morse, J.
  • Source: Ecological Applications
  • Volume: 22
  • Issue: 1
  • Year: 2012
  • Summary: Whether through sea level rise or wetland restoration, agricultural soils in coastal areas will be inundated at increasing rates, renewing connections to sensitive surface waters and raising critical questions about environmental trade-offs. Wetland restoration is, often implemented in agricultural catchments to improve water quality through nutrient removal. Yet flooding of soils can also increase production of the greenhouse gases nitrous oxide and methane, representing a potential environmental trade-off. Our study aimed to quantify and compare greenhouse gas emissions from unmanaged and restored forested wetlands, as well as actively managed agricultural fields within the North Carolina coastal plain, USA. In sampling conducted once every two months over a two-year comparative study, we found that soil carbon dioxide flux (range: 8000-64 800 kg CO2.ha(-1).yr(-1)) comprised 66-100% of total greenhouse gas emissions from all sites and that methane emissions (range: -6.87 to 197 kg CH4.ha(-1).yr(-1)) were highest from permanently inundated sites, while nitrous oxide fluxes (range: -1.07 to 139 kg N2O.ha(-1).yr(-1)) were highest in sites with lower water tables. Contrary to predictions, greenhouse gas fluxes (as CO2 equivalents) from the restored wetland were lower than from either agricultural fields or unmanaged forested wetlands. In these acidic coastal freshwater ecosystems, the conversion of agricultural fields to flooded young forested wetlands did not result in increases in greenhouse gas emissions.
  • Authors:
    • Gramig, B.
    • Reeling, C.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 146
  • Issue: 1
  • Year: 2012
  • Summary: Agricultural ecosystems are a source of greenhouse gas (GHGs) emissions and losses of nutrients to waterways. Several studies have recognized this and have documented the potential to reduce GHG fluxes and nutrient loss to waterways by using carbon offsets to fund the implementation of land retirement and afforestation. However, the ability to use land for both agricultural production and environmental conservation is also important. This study develops a novel analytical framework that is used to examine the cross-media (water and air) environmental effects of implementing offset-funded conservation practices in a working-lands setting. The framework is applied to a case study which examines the extent to which carbon pricing can affect practice implementation costs and the optimal distribution of these practices throughout an agricultural watershed. Results indicate that carbon offsets can reduce conservation practice implementation costs and have the potential to reduce greater amounts of nonpoint source pollution for a given cost of implementation. This conclusion has significant implications for policymaking, particularly with regard to using markets for GHG emissions to achieve water quality improvements where water quality trading or government conservation programs have historically been unsuccessful. (C) 2011 Elsevier B.V. All rights reserved.