• Authors:
    • Stahlman, P. W.
    • Benjamin, J. G.
    • Mikha, M. M.
    • Geier, P. W.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 1
  • Year: 2014
  • Summary: Nutrient dynamics in the calcareous eroded soils of the western United States may react differently than the acid soils in the eastern United States. The objectives of this study were to evaluate the impact of tillage practices and N treatments on changes in soil nutrient constituents. The eroded study was initiated in 2006 at the Agriculture Research Center, Hays, KS, on an Armo silt loam (fine-loamy, mixed, mesic Entic Haplustolls). Tillage practices were no-tillage (NT) and conventional tillage (CT). Beef manure (M) and urea, as commercial fertilizer (F) at low (L) and high (H) rates were applied as N sources. The control (C) treatment, with no N added, was included under both tillage practices. Annually (2006-2011) spring soil samples were taken at 0- to 15-cm and 15- to 30-cm depths. Soil chemical properties were influenced by N treatments and sampling depths, but not by tillage. Soil acidity (pH) was reduced in 2011 compared with 2006. Relative to control, more reduction in soil pH was observed with HM (21%) compared with HF treatment. Soil EC with HM and HF was approximately 2.2 times greater than LM and LF. Soil extractable P with HM substantially increased, 45.9 mg kg -1, compared with LM, 18.3 mg kg -1, at the surface 0 to 15 cm. The change in soil organic carbon (DeltaSOC) associated with M was 36-fold higher than F treatments. In general, the use of M as N source improved soil nutrient dynamics in this eroded site compared with F.
  • Authors:
    • Mekuria, M.
    • Aune, J. B.
    • Johnsen, F. H.
    • Ngwira, A.
    • Thierfelder, C.
  • Source: Journal of Soil and Water Conservation
  • Volume: 69
  • Issue: 2
  • Year: 2014
  • Summary: Understanding factors affecting farmers' adoption of improved technologies is critical to success of conservation agriculture (CA) program implementation. This study, which explored the factors that determine adoption and extent of farmers' use of the three principles of CA (i.e., minimum soil disturbance, permanent soil cover with crop residues, and crop rotations), was conducted in 10 target communities in 8 extension planning areas in Malawi. The primary data was collected using structured questionnaires administered to individual households. Triangulation with key informant interviews, field observations, and interactive discussions with farmers and farmer groups provided information behind contextual issues underpinning the statistical inferences. From a total of 15,854 households in the study areas, it is estimated that 18% of the smallholder farmers had adopted CA, representing an area of about 678 ha (1,675 ac; 2.1% of all cultivated land). Land area under CA constituted about 30% of total cultivated land among adopters. A random sample of 151 adopters and 149 nonadopters proportional with respect to adoption rates was drawn from various communities and interviewed using structured questionnaires. A total of 30 key informant interviews were conducted with stakeholders including staff of Total Land Care, government extension workers, agroinput suppliers, and lead farmers. The first stage of the Heckman model showed that hired labor, area of land cultivated, membership to farmer group, and district influenced farmers' decisions to adopt CA. The second stage of Heckman model results suggested that total cultivated land, duration of practicing CA, and district influenced farmers' decisions to extend their land to CA. Our study can be used to show the agency and social structures that are likely to influence adoption and extent of CA. Future policy should address ways to provide access to information and long-term support to farmers to enable them to embrace the technology fully.
  • Authors:
    • Meisinger, J. J.
    • Pote, D. H.
  • Source: Journal of Soil and Water Conservation
  • Volume: 69
  • Issue: 1
  • Year: 2014
  • Summary: Ammonia (NH3) volatilization from agricultural fields is important economically as a direct loss of the valuable crop nutrient nitrogen (N), but it can also be a significant environmental concern for soil, air, and water quality of nearby ecosystems. As poultry production has expanded in cropland areas of the southeastern United States, poultry litter has become a major source of crop nutrients for farmers using conservation tillage systems. However, the conventional application method of broadcasting poultry litter on the soil surface can allow as much as 60% of the applied litter N to volatilize as NH3. To provide management options that can prevent NH3 losses and help farmers use poultry litter nutrients more efficiently, a research team at USDA's Agricultural Research Service developed a prototype tractor-drawn implement for subsurface application of dry poultry litter in perennial pasture and conservation tillage systems. When compared to surface broadcasting, previous research showed that subsurface application of poultry litter decreased odor problems, increased crop yields, prevented more than 90% of nutrient losses in runoff, and prevented NH3 volatilization from perennial pasture systems. The current study was conducted to expand our knowledge regarding the effect of this litter application method on NH3 volatilization from row-crop conservation tillage systems. For two consecutive summers, field plots with a uniform high-residue surface cover of chopped wheat straw received about 5,000 kg ha(-1) (4,500 lb ac(-1)) of poultry litter applied by surface spreading with no incorporation, surface spreading followed by light disking, or subsurface banding using the prototype USDA ARS applicator. Small mobile wind tunnels monitored NH3 volatilization for at least five days after each litter treatment. Results for both years showed that NH3 losses were consistently affected by diurnal variations that were closely related to the vapor pressure deficit. Compared to conventional surface spreading of poultry litter, NH3 volatilization decreased an average of 67% when the litter application was followed by light disking, and decreased an average of 88% when the litter was applied below the soil surface using the prototype applicator. These data show that subsurface injection of dry poultry litter can preserve adequate surface cover for conservation needs while constraining NH3 losses to minimal levels, thus conserving N for row crops and reducing potential nitrogen losses to the environment.
  • Authors:
    • Sainju, U. M.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 4
  • Year: 2014
  • Summary: To determine farm C credit and reduce global warming potential, information is needed on the effect of management practices on soil C storage. The effects of tillage, cropping sequence, and N fertilization were evaluated on dryland crop biomass, surface residue C, and soil organic carbon (SOC) at the 0- to 120-cm depth in a Williams loam (fine-loamy, mixed, superactive, frigid, Typic Argiustolls) and their relationships with grain yields from 2006 to 2011 in eastern Montana. Treatments were no-till continuous malt barley ( Hordeum vulgare L.) (NTCB), no-till malt barley-pea ( Pisum sativum L.) (NTB-P), no-till malt barley-fallow (NTB-F), and conventional till malt barley-fallow (CTB-F), each with 0, 40, 80, and 120 kg N ha -1. Annualized crop grain and biomass yields, surface residue amount, and C contents were greater in NTB-P and NTCB than CTB-F and NTB-F and increased with increased N rates. At 0 to 5 and 5 to 10 cm, SOC was greater in NTB-P than CTB-F or NTCB with 40 kg N ha -1 and at 10 to 30 and 0 to 120 cm was greater in NTB-P than NTCB with 120 kg N ha -1. Surface residue C and SOC were related with grain yield and C content ( R2=0.21-0.55, P≤0.10, n=16). Greater amount of crop residue returned to the soil and turnover rate probably increased surface residue C, soil C storage, and crop yields in NTB-P with 40 and 120 kg N ha -1 than the other treatments. Soil organic matter and crop yields can be enhanced by using NTB-P with 40 kg N ha -1.
  • Authors:
    • Hatfield, P. G.
    • Lenssen, A. W.
    • Barsotti, J. L.
    • Sainju, U. M.
  • Source: Nutrient Cycling in Ecosystems
  • Volume: 99
  • Issue: 1-3
  • Year: 2014
  • Summary: Sheep (Ovis aries L.) grazing, a cost-effective method of weed control compared to herbicide application and tillage, may influence N cycling by consuming crop residue and weeds and returning N through feces and urine to the soil. The objective of this experiment was to evaluate the effect of sheep grazing compared to tillage and herbicide application for weed control on soil particulate and active soil N fractions in dryland cropping systems. Our hypothesis was that sheep grazing used for weed control would increase particulate and active soil N fractions compared to tillage and herbicide application. Soil samples collected at the 0-30 cm depth from a Blackmore silt loam were analyzed for particulate organic N (PON), microbial biomass N (MBN), and potential N mineralization (PNM) under dryland cropping systems from 2009 to 2011 in southwestern Montana, USA. Treatments were three weed management practices [sheep grazing (grazing), herbicide application (chemical), and tillage (mechanical)] as the main plot and two cropping sequences [continuous spring wheat (Triticum aestivum L.; CSW) and spring wheat-pea (Pisum sativum L.)/barley (Hordeum vulgare L.) mixture hay-fallow; W-P/B-F] as the split-plot factor arranged in randomized complete block with three replications. The PON and MBN at 0-30 cm were greater in the chemical or mechanical than the grazing treatment with CSW. The PNM at 15-30 cm was greater in the chemical or mechanical than the grazing treatment in 2009 and 2011 and at 5-15 cm was greater with W-P/B-F than CSW in 2010. From 2009 to 2011, PON at 0-30 cm and PNM at 15-30 cm reduced from 2 to 580 kg N ha(-1) year(-1) in the grazing and chemical treatments, but the rate varied from -400 to 2 kg N ha(-1) year(-1) in the mechanical treatment. Lower amount of labile than nonlabile organic matter returned to the soil through feces and urine probably reduced soil active and coarse organic matter N fractions with sheep grazing compared to herbicide application and tillage for weed control. Reduction in the rate of decline in N fractions from 2009 to 2011 compared to the herbicide application treatment, however, suggests that sheep grazing may stabilize N fractions in the long-term if the intensity of grazing is reduced. Animal grazing may reduce soil N fractions in annual cropping systems in contrast to known increased fractions in perennial cropping systems.
  • Authors:
    • Carvalho, P. C. de F.
    • Anghinoni, I.
    • Assmann, J. M.
    • Ferreira, A. O.
    • Amado, T. J. C.
    • Silva, F. D. da
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 190
  • Year: 2014
  • Summary: Brazil has the world's second-largest cattle herd and second-largest no-till grain crop area. However, these activities are not frequently integrated because there is a widespread perception that cattle have a negative effect on cropping, especially when high crop yields are a goal. This misunderstanding of the synergy between pastures, livestock and crops is linked to overgrazing at the pasture rotation phase, which causes a decline in soil quality. Few studies have investigated the effect of pasture grazing intensities on soil carbon (C) balance and soil quality in subtropical environments. This work assessed the effects of different grazing intensities (0.10, 0.20, 0.30 and 0.40 m sward height) on soil C indices and animal productivity in a clay Haplorthox. The crop-livestock system model was a soybean/ryegrass plus black oat annual rotation managed for 10 years, using a randomized complete block design with three replications. Grazing intensity affected the quantity and composition of soil C input. Under heavy grazing with limited soil C input, there was a decrease in pasture and an increase in soybean participation in total C input. Soil organic C (0-0.20 m) under different grazing intensities had a linear relationship with C stratification ratio, C management index (CMI) and C pool index. Our results suggest that integrated crop-livestock systems could act as atmospheric C sources or sinks, depending on the grazing intensity. Pastures managed at 0.20 and 0.40 m height had the best balance between CMI and animal daily gain. The best balance between CMI and live weight gain per unit area occurred in sward height of 0.20 m.
  • Authors:
    • Sperow, M.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 193
  • Year: 2014
  • Summary: The Intergovernmental Panel on Climate Change (IPCC) provides a method to estimate soil organic carbon (SOC) stock changes relative to the SOC stock under native vegetation. This manuscript modifies the IPCC approach to use the ending SOC stock from the previous inventory as the SOC stock that is changed by land use and management activities during the next inventory and to track the crop rotation and tillage intensity through three inventories. The approach allows annual rates of change of carbon sequestration from different historic land uses and management to be estimated explicitly for each assessment point based on the effect of previous land use and management. The model generates 3524 unique annual SOC sequestration rates that vary by land use and management history on U.S. agricultural land based on the 30 SOC stock reference values provided by IPCC documentation. An average of 0.33 Mg C ha -1 yr -1 is stored when cropland that was conventionally tilled in two previous inventories is set-aside in the third inventory, but only 0.14 Mg C ha -1 yr -1 when it is conventionally tilled in the first inventory and no-till in the second inventory before it is set aside. Incorporating a winter cover on cropland that was conventionally tilled in the first inventory and no-till in the second and third inventories is estimated to store 0.49 Mg C ha -1 yr -1, but could store 0.81 Mg C ha -1 yr -1 if it was conventionally tilled in the first two inventories and under no-till in the final inventory. Cropland under conventional tillage in the first two inventories and no-till the final inventory could store an average of 0.34 Mg C ha -1 yr -1, but cropland under conventional tillage in the first, reduced tillage in the second, and no-till in the third inventory is estimated to store 0.19 Mg C ha -1 yr -1. The detailed annual rates of SOC stock change estimated using the approach is useful for economic or other analyses and for policymakers.
  • Authors:
    • López-Solanilla, E.
    • Navas, M.
    • García-Marco, S.
    • Tellez-Rio, A.
    • Rees, R. M.
    • Tenorio, J. L.
    • Vallejo, A.
  • Source: Biology and Fertility of Soils
  • Volume: 51
  • Year: 2014
  • Summary: Lower greenhouse gas (GHG) emissions from legume-based cropping systems have encouraged their use to deliver mitigation in agricultural systems. Considerable uncertainties remain about the interaction of legumes with long-term tillage systems on GHG emissions under rainfed agroecosystems. In this context, a field experiment was undertaken under a rainfed vetch crop to evaluate the effect of three long-term tillage systems (i.e. no tillage (NT), minimum tillage (MT) and conventional tillage (CT)) on nitrous oxide (N2O) and methane (CH4) emissions for 1 year. Different N2O flux patterns were observed among tillage systems during the growth period of vetch, which depended on the soil conditions favouring nitrification and denitrification. The NT system maintained a higher sink for N2O than MT and CT from January to mid-April, which significantly reduced N2O emissions at this stage. In this period, denitrification capacity and nirK gene numbers were higher for MT than NT and CT. Additionally, an increase in soil NO 3 - content and more favourable denitrification conditions in MT and NT than in CT for the last crop period increased N2O emissions in conservation tillage systems. Total annual N2O losses were significantly higher in MT (124.2 g N2O-N ha-1) than NT (51.1 g N2O-N ha-1) and CT (54 g N2O-N ha-1) in a vetch crop. Low net uptake of CH4 was observed for all tillage systems. These results suggested that long-term NT may be a better option than MT to mitigate GHG emissions in rainfed legume-cereal rotation. © 2014 Springer-Verlag Berlin Heidelberg.
  • Authors:
    • Sainju, Upendra M.
    • Wang, Jun
  • Source: PLOS ONE
  • Volume: 9
  • Issue: 8
  • Year: 2014
  • Summary: Soil labile C and N fractions can change rapidly in response to management practices compared to non-labile fractions. High variability in soil properties in the field, however, results in nonresponse to management practices on these parameters. We evaluated the effects of residue placement (surface application [or simulated no-tillage] and incorporation into the soil [or simulated conventional tillage]) and crop types (spring wheat [Triticum aestivum L.], pea [Pisum sativum L.], and fallow) on crop yields and soil C and N fractions at the 0-20 cm depth within a crop growing season in the greenhouse and the field. Soil C and N fractions were soil organic C (SOC), total N (STN), particulate organic C and N (POC and PON), microbial biomass C and N (MBC and MBN), potential C and N mineralization (PCM and PNM), NH4-N, and NO3-N concentrations. Yields of both wheat and pea varied with residue placement in the greenhouse as well as in the field. In the greenhouse, SOC, PCM, STN, MBN, and NH4-N concentrations were greater in surface placement than incorporation of residue and greater under wheat than pea or fallow. In the field, MBN and NH4-N concentrations were greater in no-tillage than conventional tillage, but the trend reversed for NO3-N. The PNM was greater under pea or fallow than wheat in the greenhouse and the field. Average SOC, POC, MBC, PON, PNM, MBN, and NO3-N concentrations across treatments were higher, but STN, PCM and NH4-N concentrations were lower in the greenhouse than the field. The coefficient of variation for soil parameters ranged from 2.6 to 15.9% in the greenhouse and 8.0 to 36.7% in the field. Although crop yields varied, most soil C and N fractions were greater in surface placement than incorporation of residue and greater under wheat than pea or fallow in the greenhouse than the field within a crop growing season. Short-term management effect on soil C and N fractions were readily obtained with reduced variability under controlled soil and environmental conditions in the greenhouse compared to the field. Changes occurred more in soil labile than non-labile C and N fractions in the greenhouse than the field.
  • Authors:
    • Kwaw-Mensah, D.
    • Douelle, A.
    • Al-Kaisi, M. M.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 6
  • Year: 2014
  • Summary: Soil tillage can affect the formation and stability of soil aggregates. The disruption of soil structure weakens soil aggregates to be susceptible to the external forces of water, wind, and traffic instantaneously, and over time. The choice of tillage system or land management changes the soil physical condition and soil organic matter content, which is an essential factor in building soil aggregates. This study was conducted to investigate the effects of different tillage systems on the rate of decay of different sizes of soil aggregate fractions and other associated properties over time as subjected to a continuous wetting process. This research was conducted on a long-term tillage study, established in 2002 at the Iowa State University Agronomy Research Farm near Ames, Iowa. The soil association in this study is Clarion-Nicollet-Webster (Clarion [fine-loamy, mixed, mesic, Typic Hapluduolls], Nicollet [fine-loamy, mixed, mesic, Aquic Hapluduolls], and Webster [fine-loam, mixed, mesic, Typic Endoaquolls]). The experimental design was a randomized complete block design with four replications. Main plot treatments were five tillage systems: moldboard-plow, chisel-plow, deep-rip, strip-till, and no-till. The cropping system was corn (Zea mays L.)-soybean (Glycine max L.) rotation. Wet aggregate stability was measured using the Wet Sieving Apparatus (Eijkelkamp, Agrisearch Equipment. Art no. 08.13). Soil organic carbon (SOC) and soil total nitrogen (N) were analyzed by dry combustion using CHN Analyzer (TruSpec CHN Version 2.5x). Results show no-till with the highest carbon (C) content and the highest macro-and microaggregate stability over time. The findings also show a strong relationship between the increase in SOC content and the stability of macro-and microaggregate under continuous wetting process. Furthermore, the findings suggest that aggregate stability and moisture content are highly correlated with SOC content, and the rate of decay of both aggregate sizes (macro and micro) is highly influenced by the intensity of tillage. The implication of this research is the importance of no-till not only in increasing the stability of micro- and macroaggregates and SOC storage, but also in its effect on increasing the stability of all aggregate fractions in continuous wet conditions for extended periods of time.