• Authors:
    • Hartman, J. C.
    • Orozco, R. A.
    • Nippert, J. B.
    • Springer, C. J.
  • Source: Biomass and Bioenergy
  • Volume: 35
  • Issue: 8
  • Year: 2011
  • Summary: Switchgrass ( Panicum virgatum L.) is a broadly adapted warm-season grass species native to most of the central and eastern United States. Switchgrass has been identified as a potential biofuel species because it is a native species that requires minimal management, and has a large potential to sequester carbon underground. Since the 1990's, switchgrass has been bred to produce cultivars with increased biomass and feedstock quality. This review addresses potential ecological consequences of widespread switchgrass cultivation for biofuel production in the central United States. Specifically, this review address the ecological implications of changing use of marginal and CRP land, impacts on wildlife, potentials for disease and invasions, and changes in soil quality through reductions in erosion, decomposition rates, and carbon sequestrations. A central theme of the review is the utility of maintaining landscape heterogeneity during switchgrass biofuel production. This includes implementing harvest rotations, no till farming, and mixed species composition. If negative ecological consequences of switchgrass cultivation are minimized, biofuel production using this species has economical and environmental benefits.
  • Authors:
    • Balkcom, K. S.
    • Burmester, C. H.
  • Source: Better Crops With Plant Food
  • Volume: 95
  • Issue: 3
  • Year: 2011
  • Summary: Increased no-till or reduced tillage within Alabama wheat fields has raised research questions on how the trend might impact optimal N fertilizer rates and timings. Monitoring tiller growth as a means to predict N requirements was another option assessed across major soil types within the region.
  • Authors:
    • Avci, M.
  • Source: Agronomy for Sustainable Development
  • Volume: 31
  • Issue: 2
  • Year: 2011
  • Summary: Central Anatolian soils have high risk of erosion, degradation and intensive cultivation. Consequently, they are in danger of exhausting their agricultural use unless conservation agricultural practices are adopted. Conservation agriculture is a key tool in sustainable production systems throughout the world and is developed around soil management technology that minimizes soil disturbance, maximizes the soil cover and promotes crop diversity to offer benefits to farmers and to the environment. It has been particularly effective at sustaining crop production in semi-arid rain-fed regions such as the Central Anatolian soils, where potential evaporation exceeds precipitation during most months of the year, dry farming is extensively practiced, water and wind erosion is common, and proper application of water- and soil-conserving tillage technology is critical. The area under plow expanded its limits as the number of tractors in agriculture dramatically increased in the 1960s. This is the starting point for inappropriate use of the agricultural land. The conservation agricultural technologies, therefore, are of utmost importance for the region. Common farmers' practices of a fallow-wheat system in the central plateau of Turkey are incompatible with the conservation agriculture concept. The objective of this review is to re-evaluate the performances of the partial and full conservation tillage practices previously tried in the region. This review reached the following conclusions: (1) agreeing with the conservation principles, fall tillage as a primary operation in the fallow phase was found to be useless compared with leaving the land without tillage; (2) therefore, much research has focused on spring tillage as a primary operation and employed conventional, semi-conservative and conservative methods. Results showed that the conventional system, in addition to being ecologically unfriendly, is unprofitable as compared with other conservation practices regarding the updated cost analysis; (3) similarly, tillage depth in primary spring tillage was determined to be shallower than the depths currently practiced by farmers, in agreement with the conservation principles; (4) fallow tillage operations in summer to create dust mulch for eliminating soil moisture loss did not increase the crop yields and soil moisture as compared with chemical fallow; (5) no-till fallow was similar to the conventional clean fallow system in terms of moisture and yield levels. However, no-tillage resulted in 50% reduction in the cost of tillage besides its ecologically-friendly effects; (6) the existing dryland agricultural systems in the plateau should be transformed into or changed toward sustainable systems, although further research is required on residue and stubble management, and integrated weed control methods to drill the soil with high amounts of residue on the field.
  • Authors:
    • Attard, E.
    • Recous, S.
    • Chabbi, A.
    • Berranger, C. de
    • Guillaumaud, N.
    • Labreuche, J.
    • Philippot, L.
    • Schmid, B.
    • Roux, X. le
  • Source: Global Change Biology
  • Volume: 17
  • Issue: 5
  • Year: 2011
  • Summary: Land-use practices aiming at increasing agro-ecosystem sustainability, e.g. no-till systems and use of temporary grasslands, have been developed in cropping areas, but their environmental benefits could be counterbalanced by increased N2O emissions produced, in particular during denitrification. Modelling denitrification in this context is thus of major importance. However, to what extent can changes in denitrification be predicted by representing the denitrifying community as a black box, i.e. without an adequate representation of the biological characteristics (abundance and composition) of this community, remains unclear. We analysed the effect of changes in land uses on denitrifiers for two different agricultural systems: (i) crop/grassland conversion and (ii) cessation/application of tillage. We surveyed potential denitrification (PD), the abundance and genetic structure of denitrifiers (nitrite reducers), and soil environmental conditions. N 2O emissions were also measured during periods of several days on control plots. Time-integrated N 2O emissions and PD were well correlated among all control plots. Changes in PD were partly due to changes in denitrifier abundance but were not related to changes in the structure of the denitrifier community. Using multiple regression analysis, we showed that changes in PD were more related to changes in soil environmental conditions than in denitrifier abundance. Soil organic carbon explained 81% of the variance observed for PD at the crop/temporary grassland site, whereas soil organic carbon, water-filled pore space and nitrate explained 92% of PD variance at the till/no-till site, without any residual effect of denitrifier abundance. Soil environmental conditions influenced PD by modifying the specific activity of denitrifiers, and to a lesser extent by promoting a build-up of denitrifiers. Our results show that an accurate simulation of carbon, oxygen and nitrate availability to denitrifiers is more important than an accurate simulation of denitrifier abundance and community structure to adequately understand and predict changes in PD in response to land-use changes.
  • Authors:
    • Basch, G.
    • Freixial, R.
    • Carvalho, M. de
    • Barros, J. C.
  • Source: Revista de Ciências Agrárias
  • Volume: 34
  • Issue: 1
  • Year: 2011
  • Summary: The study was carried out over 2 years (2007/2008 and 2008/2009) on a private farm in the Alentejo region (Evora), in the South of Portugal where rainfed wheat is sown after the beginning of the autumn rainfall season. The wheat crop was established using no-till which permits the post-emergence application of herbicides at an early weed development stage. To control J. bufonius and different broad-leaved weeds, a mixture of two herbicides was used when the weeds were at the 3-4 pair of leaves development stage. The herbicides applied were mesosulfuron-methyl+iodosulfuron-methyl-sodium+mefenpyr-diethyl (H1) and clortoluron (H2) at two different doses. Best J. bufonius control was achieved with the higher dose of the herbicide H2 and the highest broad-leaved weeds control was obtained when the higher dose of the herbicide H1 was applied. Although no significant differences in grain yield were observed between the different herbicide treatments, there was a tendency for higher grain yields with an increase of control efficacy of Juncus bufonius L.
  • Authors:
    • Baraibar, B.
    • Ledesma, R.
    • Royo-Esnal, A.
    • Westerman, P. R.
  • Source: Crop Protection
  • Volume: 30
  • Issue: 9
  • Year: 2011
  • Summary: Harvester ants from the species Messor barbarus (L.) are important seed predators in semi-arid cereal fields of NE Spain, and can contribute substantially to weed control. However, occasionally they harvest newly sown crop seeds at sowing in autumn, or ripe cereal grains close to harvest in summer, causing yield losses. A preliminary study was conducted in 34 commercial winter cereal fields to measure yield loss, and to identify factors that influence it. The area affected by ants was measured ten days prior to the anticipated harvest date. Ant colony size, nest density, crop height, weed densities and temperatures at sowing were assessed. At sowing, harvester ants did not cause yield losses (0.2% of potential yield on average). At harvest, yield losses were generally low as well (0.6%) although occasionally higher losses were recorded (max. 9.2%). Yield losses significantly increased with increasing nest density, nest size and with number of years of no-till. The results of this study show that in 2009 yield losses caused by M. barbarus were insignificant and more than offset by the benefits provided by the destruction of weed seeds.
  • Authors:
    • Balota, E. L.
    • Machineski, O.
    • Truber, P. V.
    • Antonio, P.
    • Auler, M.
  • Source: Brazilian Archives of Biology and Technology
  • Volume: 54
  • Issue: 2
  • Year: 2011
  • Summary: The objective of this study was to evaluate the effect of different soil tillage systems and groundcover crops intercropped with orange trees on soil enzyme activities. The experiment was performed in an Ultisol soil in northwestern Parana State. Two soil tillage systems were evaluated [conventional tillage (CT) across the entire area and strip tillage (ST) with a 2-m strip width] in combination with various groundcover vegetation management systems. Soil samples were collected after five years of experimental management at a depth of 0-15 cm under the tree canopy and in the inter-row space in the following treatments: (1) CT-Calopogonium mucunoides; (2) CT-Arachis pintoi; (3) CT-Bahiagrass; (4) CT-Brachiaria humidicola; and (5) ST-B. humidicola. The soil tillage systems and groundcover crops influenced the soil enzyme activities both under the tree canopy and in the inter-row space. The cultivation of B. humidicola provided higher amylase, arylsulfatase, acid phosphatase and alkaline phosphatase than other groundcover species. Strip tillage increased enzyme activities compared to the conventional tillage system.
  • Authors:
    • Humphreys, E.
    • Yadvinder-Singh
    • Eberbach, P. L.
    • Katupitiya, A.
    • Kukal, S. S.
    • Balwinder-Singh
  • Source: Field Crops Research
  • Volume: 121
  • Issue: 2
  • Year: 2011
  • Summary: Intensive cultivation of rice and wheat in north-west India has resulted in air pollution from rice straw burning, soil degradation and declining groundwater resources. The retention of rice residues as a surface mulch could be beneficial for moisture conservation and yield, and for hence water productivity, in addition to reducing air pollution and loss of soil organic matter. Two field experiments were conducted in Punjab, India, to study the effects of rice straw mulch and irrigation scheduling on wheat growth, yield, water use and water productivity during 2006-2008. Mulching increased soil water content and this led to significant improvement in crop growth and yield determining attributes where water was limiting, but this only resulted in significant grain yield increase in two instances. There was no effect of irrigation treatment in the first year because of well-distributed rains. In the second year, yield decreased with decrease and delay in the number of irrigations between crown root initiation and grain filling. With soil matric potential (SMP)-based irrigation scheduling, the irrigation amount was reduced by 75 mm each year with mulch in comparison with no mulch, while maintaining grain yield. Total crop water use (ET) was not significantly affected by mulch in either year, but was significantly affected by irrigation treatment in the second year. Mulch had a positive or neutral effect on grain water productivity with respect to ET (WP ET) and irrigation (WP I ). Maximum WP I occurred in the treatment which received the least irrigation, but this was also the lowest yielding treatment. The current irrigation scheduling guidelines based on cumulative pan evaporation (CPE) resulted in sub-optimal irrigation (loss of yield) in one of the two years, and higher irrigation input and lower WP I of the mulched treatment in comparison with SMP-based irrigation scheduling. The results from this and other studies suggest that farmers in Punjab greatly over-irrigate wheat. Further field and modelling studies are needed to extrapolate the findings to a wider range of seasonal and site conditions, and to develop simple tools and guidelines to assist farmers to better schedule irrigation to wheat.
  • Authors:
    • Bene, C. di
    • Tavarini, S.
    • Mazzoncini, M.
    • Angelini, L. G.
  • Source: European Journal of Agronomy
  • Volume: 35
  • Issue: 3
  • Year: 2011
  • Summary: The introduction of perennials in the Mediterranean crop rotations can have a positive effect on soil organic matter (SOM) concentration, thus improving the long-term sustainability of cropping systems, affected by the progressive degradation in soil fertility. Ramie [ Boehmeria nivea (L.) Gaud.], a perennial herbaceous species used for its high quality bast fibre, has recently received renewed attention for production in Europe due to the increasing natural fibre demand globally. Little attention has been focused on the ramie cultivation management and on its effect on soil chemical characteristics. A long-term field experiment was carried out in Pisa (Central Italy, 43 degrees 40′N; 10 degrees 19′E) since 1996, with the aim to assess the long-term environmental sustainability of ramie in terms of productivity, nutrient balance, soil fertility and SOM pool. The fertiliser management of ramie consisted of 150-100-100 kg N-P-K ha -1 in the establishment year and 150-65-165 kg N-P-K ha -1 year -1 from the second year onwards. Plant nutrient uptake was analysed to optimise the crop mineral nutrition and to evaluate the nutrient balance and the efficiency of fertiliser management. The SOM dynamic was evaluated using the actual investigated data and Henin-Dupuis's equation in order to estimate the organic requirements for SOM equilibrium. Over the 13-year cultivation period, a mean value of 14 Mg ha -1 year -1 of total above-ground dry biomass was obtained. In the 0-30 cm soil depth, SOM, total nitrogen (N), available phosphorus (P), exchangeable potassium (K) and pH varied significantly throughout the cultivation period. SOM increased significantly, from 13.4 g kg -1 to 25.3 g kg -1. A significant correlation between the measured SOM and the cumulative organic matter (OM) inputs ( r2=0.908; P=0.012) was found. The average annual N and P balances were positive (equal to 14 kg ha -1 and 38 kg ha -1, respectively), while the K balance was negative (-57 kg ha -1). The results show that ramie crop has a positive effect on SOM pool, thus representing an interesting sustainable fibre crop for the Mediterranean area.
  • Authors:
    • Rangel, D.
    • Jacobson, A. R.
    • Laba, M.
    • Darnault, C.
    • Otten, W.
    • Radulovich, R.
    • Camargo, F. A. O.
    • Baveye, P. C.
  • Source: Soil Science Society of American Journal
  • Volume: 75
  • Issue: 6
  • Year: 2011
  • Summary: When the Soil Science Society of America was created, 75 yr ago, the USA was suffering from major dust storms, causing the loss of enormous amounts of topsoil as well as human lives. These catastrophic events reminded public officials that soils are essential to society's well-being. The Soil Conservation Service was founded and farmers were encouraged to implement erosion mitigation practices. Still, many questions about soil processes remained poorly understood and controversial. In this article, we argue that the current status of soils worldwide parallels that in the USA at the beginning of the 20th century. Dust bowls and large-scale soil degradation occur over vast regions in a number of countries. Perhaps more so even than in the past, soils currently have the potential to affect populations critically in several other ways as well, from their effect on global climate change, to the toxicity of brownfield soils in urban settings. Even though our collective understanding of soil processes has experienced significant advances since 1936, many basic questions still remain unanswered, for example whether or not a switch to no-till agriculture promotes C sequestration in soils, or how to account for microscale heterogeneity in the modeling of soil organic matter transformation. Given the enormity of the challenges raised by our (ab)uses of soils, one may consider that if we do not address them rapidly, and in the process heed the example of U.S. public officials in the 1930s who took swift action, humanity may not get a chance to explore other frontiers of science in the future. From this perspective, insistence on the fact that soils are critical to life on earth, and indeed to the survival of humans, may again stimulate interest in soils among the public, generate support for soil research, and attract new generations of students to study soils.