19662015
  • Authors:
    • Johnsen, T. N.
    • McLain, J. E. T.
    • Emmerich, W.
    • Martens, D. A.
  • Source: Soil & Tillage Research
  • Volume: 83
  • Issue: 1
  • Year: 2005
  • Summary: Agriculture in the southwestern USA is limited by water supply due to high evaporation and limited seasonal precipitation. Where water is available, irrigation allows for production of a variety of agricultural and horticultural crops. This review assesses the impacts of agriculture on greenhouse gas emission and sequestration of atmospheric C in soils of the hot, dry region of the southwestern USA. In Texas, conservation tillage increased soil organic C by 0.28 Mg C ha(-1) year(-1) compared with more intensive tillage. Conversion of tilled row crops to the conservation reserve program or permanent pastures increased soil organic C by 0.32 +/- 0.50 Mg C ha(-1) year(-1). Soil organic C sequestration was dependent on rotation, previous cropping, and type of conservation tillage employed. Relatively few studies have interfaced management and C cycling to investigate the impacts of grazing management on soil organic C, and therefore, no estimate of C balance was available. Irrigated crop and pasture land in Idaho had soil organic C content 10-40 Mg C ha(-1) greater than in dryland, native grassland. Soil salinity must be controlled in cropland as soil organic C content was lower with increasing salinity. Despite 75% of the region's soils being classified as calcic, the potential for sequestration of C as soil carbonate has been only scantly investigated. The region may be a significant sink for atmospheric methane, although in general, trace gas flux from semiarid soils lacks adequate characterization. Agricultural impacts on C cycling will have to be better understood in order for effective C sequestration strategies to emerge. Published by Elsevier B.V.
  • Authors:
    • Sherrod, L.
    • Robertson, G. P.
    • Peterson, G. A.
    • Halvorson, A. D.
    • Mosier, A. R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 72
  • Issue: 1
  • Year: 2005
  • Summary: When appraising the impact of food and fiber production systems on the composition of the Earth's atmosphere and the 'greenhouse' effect, the entire suite of biogenic greenhouse gases - carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) - needs to be considered. Storage of atmospheric CO2 into stable organic carbon pools in the soil can sequester CO2 while common crop production practices can produce CO2, generate N2O, and decrease the soil sink for atmospheric CH4. The overall balance between the net exchange of these gases constitutes the net global warming potential (GWP) of a crop production system. Trace gas flux and soil organic carbon (SOC) storage data from long-term studies, a rainfed site in Michigan that contrasts conventional tillage (CT) and no-till (NT) cropping, a rainfed site in northeastern Colorado that compares cropping systems in NT, and an irrigated site in Colorado that compares tillage and crop rotations, are used to estimate net GWP from crop production systems. Nitrous oxide emissions comprised 40-44% of the GWP from both rain-fed sites and contributed 16-33% of GWP in the irrigated system. The energy used for irrigation was the dominant GWP source in the irrigated system. Whether a system is a sink or source of CO2, i.e. net GWP, was controlled by the rate of SOC storage in all sites. SOC accumulation in the surface 7.5 cm of both rainfed continuous cropping systems was approximately 1100 kg CO2 equivalents ha-1 y-1. Carbon accrual rates were about three times higher in the irrigated system. The rainfed systems had been in NT for >10 years while the irrigated system had been converted to NT 3 years before the start of this study. It remains to be seen if the C accrual rates decline with time in the irrigated system or if N2O emission rates decline or increase with time after conversion to NT.
  • Authors:
    • Drenovsky, R. E.
    • Whisson, D. A.
    • Scow, K. M
    • Ingels, C. A.
  • Source: American Journal of Enology and Viticulture
  • Volume: 56
  • Issue: 1
  • Year: 2005
  • Summary: Several cover crop mixes were planted in a winegrape vineyard in Sacramento County to test their effects on vine growth, production, juice composition, soil microbial ecology, and gopher activity over a three-year period (1998 to 2000). The trial was conducted in a Vitis vinifera L. cv. Merlot vineyard on a silt loam soil. Vines were planted in 1993 on 5BB rootstock, spaced 2.1 x 3.4 m. The mixes used were: California native perennial grass (no-till), annual clover (no-till), green manure (disked), cereals (disked), and disked control. Cover crops were planted on either side of entire rows, with a disked alley separating treatment replicates. A 1.2-m herbicide strip was maintained under the vines. Drip irrigation and fertigation were applied uniformly across all treatments, but additional nitrogen fertilizer was applied to the grass mixes. Weed biomass increased in the clover mix but decreased in the native grass mix. Grapevine petiole nitrogen content was highest in the bell bean mix and very low in the native grass mix. There were very few differences in leaf water potential or pruning weights of the vines, and in yields or juice Brix, pH, or titratable acidity in any year. Cover-cropped soils had greater microbial biomass than disked or berm soils, and the no-till mixes had greater microbial biomass than the disked mixes. Gophers were very numerous in 1999 only, with nearly all activity exclusively in the clover mix.
  • Authors:
    • Strickland, T. C.
    • Bednarz, C. W.
    • Truman, C. C.
    • Potter, T. L.
    • Bosch, D. D.
  • Source: Transactions of the ASAE
  • Volume: 48
  • Issue: 6
  • Year: 2005
  • Summary: Conservation tillage has significant potential as a water management tool for cotton production on sandy, drought-prone soils. Plant residue remaining at the soil surface from prior crops serves as a vapor barrier against water loss, reduces raindrop impact energy, slows surface runoff, and often increases infiltration. By increasing infiltration, the potential for greater plant-available water can be enhanced and irrigation requirements reduced. Five years of data were collected to quantify the hydrologic differences between strip till and conventional till production systems. Surface runoff and lateral subsurface flow were measured on six 0.2 ha plots in South Georgia in order to quantify the water-related effects of conservation tillage. Significant differences in surface and subsurface water losses were observed between the conventional and strip tilled plots. Surface runoff from the conventionally tilled plots exceeded that from the strip tilled plots, while subsurface losses were reversed. Surface runoff losses from the conventionally tilled plots exceeded those from the strip tilled plots by 81% (129 mm/year). Shallow lateral subsurface losses from the strip tilled plots exceeded those from the conventionally tilled plots by 73% (69 mm/year). Overall, a net annual gain of 60 mm of water was observed for the strip tilled plots.
  • Authors:
    • Cardon, G.
    • Qian, Y.
    • Dillon, M.
    • Sparks, R.
    • Barbarick, K.
    • Delgado, J. A.
    • Al-Sheikh, A.
  • Source: Soil & Tillage Research
  • Volume: 81
  • Issue: 2
  • Year: 2005
  • Summary: The potential for wind erosion in South Central Colorado is greatest in the spring, especially after harvesting of crops such as potato (Solanum tuberosum L.) that leave small amounts of crop residue in the surface after harvest. Therefore it is important to implement best management practices that reduce potential wind erosion and that we understand how cropping systems are impacting soil erosion, carbon dynamics, and properties of rangeland sandy soils. We evaluate the effects of cropping systems on soil physical and chemical properties of rangeland sandy soils. The cropping system included a small grain-potato rotation. An uncultivated rangeland site and three fields that two decades ago were converted from rangeland into cultivated center-pivot-irrigation-sprinkler fields were also sampled. Plant and soil samples were collected in the rangeland area and the three adjacent cultivated sites. The soils at these sites were classified as a Gunbarrel loamy sand (Mixed, frigid Typic Psammaquent). We found that for the rangeland site, soil where brush species were growing exhibited C sequestration and increases in soil organic matter (SOM) while the bare soil areas of the rangeland are losing significant amounts of fine particles, nutrients and soil organic carbon (SOM-C) mainly due to wind erosion. When we compared the cultivated sites to the uncultivated rangeland, we found that the SOM-C and soil organic matter nitrogen (SOM-N) increased with increases in crop residue returned into the soils. Our results showed that even with potato crops, which are high intensity cultivated cropping systems, we can maintain the SOM-C with a rotation of two small grain crops (all residue incorporated) and one potato crop, or potentially increase the average SOM-C with a rotation of four small grain crops (all residue incorporated) and one potato crop. Erosion losses of fine silt and clay particles were reduced with the inclusion of small grains. Small grains have the potential to contribute to the conservation of SOM and/or sequester SOM-C and SOM-N for these rangeland systems that have very low C content and that are also losing C from their bare soils areas (40%). Cultivation of these rangelands using rotations with at least two small grain crops can reduce erosion and maintain SOM-C and increasing the number of small grain crops grown successfully in rotation above two will potentially contribute to C and N sequestration as SOM and to the sequestration of macro- and micro-nutrients.
  • Authors:
    • Arkebauer, Timothy J.
    • Amos, Brigid
    • Cardon, G.
    • Qian, Y.
    • Dillon, M.
    • Sparks, R.
    • Doran, John W.
    • Barbarick, K.
    • Delgado, J. A.
    • Al-Sheikh, A.
  • Source: Soil Science Society of America Journal
  • Volume: 69
  • Issue: 2
  • Year: 2005
  • Summary: An understanding of the effect of fertility management on soil surface fluxes of CO2, N2O, and CH4 is essential in evaluating C sequestration measures that attempt to increase the amount of crop residue returned to the soil through increased fertilizer inputs. In this study, soil surface CO2 flux was measured over a 27-mo sampling period in continuous maize (Zea mays L.) plots managed under either an intensive fertility regime (M2) or recommended best management (M1). Flux was significantly higher in the M2 treatment on only 2 d during the first growing season. Annual estimates of soil surface CO2 flux, based on a modified exponential equation that incorporates leaf area index (LAI) to predict temporal changes in soil respiration, averaged 11 550 kg C ha-1 yr-1 for both treatments (approximately 31.64 kg C ha-1 d-1 on average). Within row soil surface CO2 flux was, on average, 64% higher than between row flux. Plant population did not significantly affect measured soil surface CO2 flux. While fertility management had no significant effect on CH4 flux, N2O flux as measured on 3 d during the 2000 growing season was significantly higher in the M2 treatment. In 2001, no significant differences in N2O flux were observed, possibly due to changes in N management and irrigation method. Electrical conductivity measured during the 2000 and 2001 growing seasons was significantly higher in the M2 treatment while pH measured during the 2001 season was significantly lower for M2.
  • Authors:
    • Delgado, J. A.
    • Bausch, W.
  • Source: Precision Agriculture
  • Volume: 6
  • Issue: 6
  • Year: 2005
  • Summary: Spatial and temporal variability of soil nitrogen (N) supply together with temporal variability of plant N demand make conventional N management difficult. This study was conducted to determine the impact of residual soil nitrate-N (NO3-N) on ground-based remote sensing management of in-season N fertilizer applications for commercial center-pivot irrigated corn (Zea mays L.) in northeast Colorado. Wedge-shaped areas were established to facilitate fertigation with the center pivot in two areas of the field that had significantly different amounts of residual soil NO3-N in the soil profile. One in-season fertigation (48 kg N ha-1) was required in the Bijou loamy sand soil with high residual NO3-N versus three in-season fertigations totaling 102 kg N ha-1 in the Valentine fine sand soil with low residual NO3-N. The farmer applied five fertigations to the field between the wedges for a total in-season N application of 214 kg N ha-1. Nitrogen input was reduced by 78% and 52%, respectively, in these two areas compared to the farmer's traditional practice without any reductions in corn yield. The ground-based remote sensing management of in-season applied N increased N use efficiency and significantly reduced residual soil NO3-N (0-1.5 m depth) in the loamy sand soil area. Applying fertilizer N as needed by the crop and where needed in a field may reduce N inputs compared to traditional farmer accepted practices and improve in-season N management.
  • Authors:
    • Sarpe,N.
    • Poienaru,S.
  • Source: Lucrari Stiintifice, Universitatea de Stiinte Agricole Si Medicina Veterinara "Ion Ionescu de la Brad" Iasi, Seria Agronomie, Romania
  • Volume: 48
  • Year: 2005
  • Summary: Results are presented of an experiment in the Plain of Danube (Romania) with genetically modified soyabean (0094RR) in successive culture after barley under no-stripping system. Roundup Ready (containing 360 g glyphosate/l) was used to control grassy weeds, including Sorghum halepense. Roundup Ready at 3+3 l/ha resulted in 100% control of annual and perennial grasses. It also recorded the highest yield of 2800 kg/ha under 2 irrigations with a watering rate of 400 m 3/ha. With barley culture+soyabean in successive culture on the traditional system, 122 l of fuel oil was consumed for mechanical work, whereas on the system of no-stripping only 48 l/ha. Calculations concerning economic efficiency revealed that barley culture+soyabean in successive culture recorded a profit of ~28 million lei/ha.
  • Authors:
    • Cooke, F. T.,Jr.
    • Robinson, J. R. C.
    • Martin, S. W.
    • Parvin, D.
  • Source: Crop Management
  • Issue: April
  • Year: 2005
  • Summary: This study compared conventional, reduced tillage and no-till systems for cotton, maize, soyabean and sorghum in the Mississippi Delta. Most of the necessary parameters (e.g. yields, costs, equipment, field operations) were obtained from published budgets. The conventional systems typically involved subsoiling, discing, field cultivation, hipping and in-season cultivation. The reduced tillage systems substituted herbicides for heavy pre-plant soil preparation and in-season cultivation, while no-till systems substituted herbicides for all tillage operations. A whole-farm, mixed integer programming model was developed to determine the most profitable crop/tillage combinations at different acreage sizes, assess the actual economies of size (in dollars per acre) in row crop farming, determine the number of acres required to maximize economic viability, determine the best acreage size to minimize or optimize full-time labour, and evaluate profitability trade-offs, including farm programme eligibility, under different tillage systems.
  • Authors:
    • Zamfir, M. C.
    • Mitu, D.
  • Source: Probleme de agrofitotehnie teoretica si aplicata
  • Volume: 27
  • Issue: 2
  • Year: 2005
  • Summary: During 2001-03 in Teleorman, 14 Romanian maize hybrids (Campion, Rapsodia, Danubiu, Paltin, Olt, F. 376, Faur, Partizan, Octavian, Granit, F. 322, Milcov, Orizont and Vultur) were studied under different situations, such as irrigation and dryland, and under 3 types of drought during the maize vegetation: drought in the second part of summer (2001), drought in the first part of summer (2002), and long lasting drought (2003). Paltin, Campion, Rapsodia, Danubiu, Faur and Olt had a good behaviour under irrigated or dryland conditions, but Partizan, Orizont, Vultur, Octavian and Granit proved to be sensitive to drought. During dry years, the flowering delay (days) and the frequency of sterile plants had determined significant diminution of maize yield. The effects of drought on maize yield differed, depending on its type, intensity and way of action, under different stages of growth and development of the plants. Long lasting and pronounced drought over the whole period of maize vegetation resulted in the highest losses in yield (76-77%) compared to partial droughts during the second part of summer (62-65%) or during the first part of vegetation growth (26-30%). To reduce the negative effect of drought on maize, the cultivation of 2-3 hybrids with different earliness is recommended, which ensures a more efficient use of the distribution of rainfall during the maize vegetation as well as a reduced variation of harvest.