• Authors:
    • Lenssen, A. W.
    • Waddell, J. T.
    • Johnson, G. D.
    • Carlson, G. R.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Improved nitrogen use efficiency would be beneficial to agroccosystem sustainability in the northern Great Plains of the USA. The most common rotation in the northern Great Plains is fallow-spring wheat. Tillage during fallow periods controls weeds, which other-wise would use substantial amounts of water and available nitrogen, decreasing the efficiency of fallow. Chemical fallow and zero tillage systems improve soil water conservation, and may improve nitrogen availability to subsequent crops. We conducted a field trial from 1998 through 2003 comparing nitrogen uptake and nitrogen use efficiency of crops in nine rotations under two tillage systems, conventional and no-till. All rotations included spring wheat, two rotations included field pea, while lentil, chickpea, yellow mustard, sunflower, and safflower were present in single rotations with wheat. Growing season precipitation was below average in 3 of 4 years, resulting in substantial drought stress to crops not following fallow. In general, rotation had a greater influence on spring wheat nitrogen accumulation and use efficiency than did tillage system. Spring wheat following fallow had substantially higher N accumulation in seed and biomass, N harvest index, and superior nitrogen use efficiency than wheat following pea, lentil, chickpea, yellow mustard, or wheat. Preplant nitrate-N varied widely among years and rotations, but overall, conventional tillage resulted in 9 kg ha(-1) more nitrate-N (060 cm) for spring wheat than did zero tillage. However, zero tillage spring wheat averaged 11 kg ha(-1) more N in biomass than wheat in conventional tillage. Nitrogen accumulation in pea seed, 45 kg ha(-1) was superior to that of all alternate crops and spring wheat, 17 and 23 kg ha(-1), respectively. Chickpea, lentil, yellow mustard, safflower, and sunflower did not perform well and were not adapted to this region during periods of below average precipitation. During periods of drought, field pea and wheat following fallow had greater nitrogen use efficiency than recropped wheat or other pulse and oilseed crops.
  • Authors:
    • Sainju, U. M.
    • Caesar-TonThat, T.
    • Lenssen, A. W.
    • Evans, R. G.
    • Kolberg, R.
  • Source: Soil Science Society of America Journal
  • Volume: 71
  • Issue: 6
  • Year: 2007
  • Summary: Long-term management practices are needed to increase dryland C storage and improve soil quality. We evaluated the 21-yr effects of combinations of tillage and cropping sequences on dryland crop biomass (stems + leaves) returned to the soil, residue C, and soil C fractions at the 0- to 20-cm depth in a Dooley sandy loam (fine-loamy, mixed, frigid, Typic Argiborolls) in eastern Montana. Treatments were no-till continuous spring wheat (Triticum aestivum L.) (NTCW), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat-barley (Hordeum vulgare L.) (1984-1999) followed by spring wheat-pea (Pisum sativum L.) (2000-2004) (FSTW-B/P), and spring-tilled spring wheat-fallow (STW-F). Carbon fractions were soil organic C (SOC), soil inorganic C (SIC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Mean crop biomass was 53 to 66% greater in NTCW, STCW, FSTCW, and FSTW-B/P than in STW-F. Soil surface residue amount and C content in 2004 were 46 to 60% greater in NTCW and FSTCW than in STW-F As a result, soil C fractions at 0 to 20 cm were 23 to 141 % greater in all other treatments than in STW-F due to increased C input. At 0 to 5 cm, SOC, SIC, POC, and PCM were greater in NTCW than in FSTW-B/P. At 5 to 20 cm, POC was greater in NTCW than in FSTW-B/P and PCM was greater in STCW than in FSTCW. Long-term reduced tillage with continuous nonlegume cropping increased dryland crop biomass, residue and soil C storage, and soil quality by increasing microbial biomass and activities compared with a conventional system such as STW-F.
  • Authors:
    • Lenssen, A.
    • Caesar-Thonthat, T.
    • Waddell, J.
    • Sainju, U. M.
  • Source: Soil & Tillage Research
  • Volume: 93
  • Issue: 2
  • Year: 2007
  • Summary: Soil and crop management practices may alter the quantity, quality, and placement of plant residues that influence soil C and N fractions. We examined the effects of two tillage practices [conventional till (CT) and no-till (NT)] and five crop rotations [continuous spring wheat (Triticum aestivum L.) (CW), spring wheat-fallow (W-F), spring wheat-lentil (L-ens culinaris Medic.) (W-L), spring wheat-spring wheat-fallow (W-W-F), and spring wheat-pea (Pisum sativum L.)-fallow (W-P-F)] on transient land previously under 10 years of Conservation Reserve Program (CRP) planting on the amount of plant biomass (stems + leaves) returned to the soil from 1998 to 2003 and soil C and N fractions within the surface 20 cm in March 2004. A continued CRP planting was also included as another treatment for comparing soil C and N fractions. The C and N fractions included soil organic C (SOC), soil total N (STN), microbial biomass C and N (MBC and MBN), potential C and N mineralization (PCM and PNM), and NH4-N and NO3-N contents. A field experiment was conducted in a mixture of Scobey clay loam (fine-loamy, mixed, Aridic Argiborolls) and Kevin clay loam (fine, montmorillonitic, Aridic Argiborolls) in Havre, MT, USA. Plant biomass yield varied by crop rotation and year and mean annualized biomass was 45-50% higher in CW and W-F than in W-L. The SOC and PCM were not influenced by treatments. The MBC at 0-5 cm was 26% higher in W-W-F than in W-F. The STN and NO3-N at 5-20 cm and PNM at 0-5 cm were 17-1206% higher in CT with W-L than in other treatments. Similarly, MBN at 0-5 cm was higher in CT with W-L than in other treatments, except in CT with W-F and W-P-F. Reduction in the length of fallow period increased MBC and MBN but the presence of legumes, such as lentil and pea, in the crop rotation increased soil N fractions. Six years of tillage and crop rotation had minor influence on soil C and N storage between croplands and CRP planting but large differences in active soil C and N fractions.
  • Authors:
    • Young, D. L.
    • Schillinger, W. F.
    • Kennedy, A. C.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 120
  • Issue: 2-4
  • Year: 2007
  • Summary: The tillage-based winter wheat (Triticum aestivum L.)-summer fallow (WW-SF) cropping system has dominated dryland farming in the Pacific Northwest USA for 125 years. We conducted a large-scale multidisciplinary 8-year study of annual (i.e., no summer fallow) no-till cropping systems as an alternative to WW-SF. Soft white and hard white classes of winter and spring wheat, spring barley (Hordeum vulgare L.), yellow mustard (Brassica hirta Moench), and safflower (Carthamus tinctorius L.) were grown in various rotation combinations. Annual precipitation was less than the long-term average of 301 mm in 7 out of 8 years. Rhizoctonia bare patch disease caused by the fungus Rhizoctonia solani AG-8 appeared in year 3 and continued through year 8 in all no-till plots. All crops were susceptible to rhizoctonia, but bare patch area in wheat was reduced, and grain yield increased, when wheat was grown in rotation with barley every other year. Remnant downy brome (Bromus tectorum L.) weed seeds remained dormant for 6 years and longer to heavily infest recrop winter wheat. There were few quantifiable changes in soil quality due to crop rotation, but soil organic carbon (SOC) increased in the surface 0-5 cm depth with no-till during the 8 years to approach that found in undisturbed native soil. Annual no-till crop rotations experienced lower average profitability and greater income variability compared to WW-SF. Yellow mustard and safflower were not economically viable. Continuous annual cropping using no-till provides excellent protection against wind erosion and shows potential to increase soil quality, but the practice involves high economic risk compared to WW-SF. This paper provides the first comprehensive multidisciplinary report of long-term alternative annual no-till cropping systems research in the low-precipitation region of the Pacific Northwest.
  • Authors:
    • Shah, Z.
    • Stromberger, M.
    • Westfall, D.
  • Source: Applied Soil Ecology
  • Volume: 35
  • Issue: 1
  • Year: 2007
  • Summary: In degraded agricultural soils, organic C levels can be increased and conserved by adopting alternative management strategies such as no-tillage and increased cropping intensity. However, soil microbial community responses to increased soil organic C (SOC) may be constrained due to water limitations in semi-arid dryland agroecosystems. The purpose of this study was to assess SOC, microbial biomass C (MBC) and community ester-linked fatty acid methyl ester (EL-FAME) composition under winter wheat ( Triticum aestivum L.) in no-till systems of wheat-corn ( Zea mays L.)-fallow (WCF), wheat-wheat-corn-millet ( Panicum miliaceum L.) (WWCM), wheat-corn-millet (WCM), opportunity cropping (OPP), and perennial grass across a potential evapotranspiration gradient in eastern Colorado. Rotations of WWCM and OPP, in which crops are chosen based on available soil water at the time of planting rather than according to a predetermined rotation schedule, increased levels of SOC to those measured under perennial grass. However, MBC under OPP cropping accounted for the smallest fraction (2.0-3.6%) of SOC compared to other systems, in which MBC ranged from 2.4 to 6.3% of SOC. Microbial community structure was most divergent between OPP-cropped and perennial grass soils, whereas few differences were observed among microbial communities of the WCF, WCM, and WWCM rotations. Compared to perennial grass and other cropping systems, microbial biomass in OPP-cropped soil was low and contained less of the arbuscular mycorrhizal fungal biomarker 16:1omega5 c. Microbial stress, as indicated by the ratio of 17:0 cy to 16:1omega7 c, was greatest under OPP and WCF cropping. In contrast, soils under perennial grass contained lower ratios of bacterial:fungal EL-FAMEs and higher levels of MBC, ratios of MBC:SOC, and relative abundances of 16:1omega5 c. Across locations, SOC and moisture content increased as soil texture became finer, whereas trends in MBC and community structure followed the potential evapotranspiration gradient. Soil from the high potential evapotranspiration site contained the lowest level of MBC but greater relative amounts of 16:1omega5 c and lower ratios of stress indicator and bacterial:fungal EL-FAMEs compared to soil located at the moderate and low potential evapotranspiration sites. Indistinct microbial communities under WCF, WCM, and WWCM could be explained by EL-FAME limitations to detecting slight differences in microbial community structure or to the overwhelming response of microbial communities to environmental rather than management conditions. Further research is needed to assess potential legacy effects of long-term agricultural management that may mask microbial responses to recent management change, as well as to identify conditions that lead to high microbial community resiliency in response to management so that communities are similar under a given crop despite different preceding crops.
  • Authors:
    • Weiss, M. J.
    • Pike, K. S.
    • Buntin, G. D.
    • Webster, J. A.
  • Source: Handbook of small grain insects
  • Year: 2007
  • Summary: This handbook is designed primarily for the practitioners of integrated pest management programmes in small grains, growers, crop consultants, extension agents, and company agronomists and sales representatives. Its primary objective is to provide fundamental and useful information about managing (through cultural, plant resistance, biological and chemical methods) small grain insects throughout the United States and Canada. Although it focuses on insect pests of small grains, noninsect pests (e.g. mites) also are covered. Crops covered in this handbook are wheat, barley, oats, rye and triticale, with an emphasis on wheat. The first three sections provide information about small grains and their production, principles and practices of small grain insect management, and an overview of the pest injury to small grains by insects, weeds, and plant pathogens. The remainder of the handbook is devoted to discussions of insect and mite pests of small grains and to beneficial organisms, including insect pathogens, parasitoids and predators.
  • Authors:
    • Gomezdelcampo, E.
    • Murphy, R. P.
    • Evans, J. E.
  • Source: JOURNAL OF GREAT LAKES RESEARCH
  • Volume: 33
  • Issue: SI2
  • Year: 2007
  • Summary: The Sandusky River basin, located in northwest Ohio, has been influenced by agriculture since the late-1800s. In 2003, the Ohio Environmental Protection Agency identified various tributaries of the Sandusky River as failing to meet biological water quality standards mainly due to siltation. To assess the effectiveness of best management practices (BMPs), a cutoff channel of the Sandusky River in Crawford County, Ohio was used as a unique archive of channel bed material that existed in the previous channel. Historical aerial photographs and USGS peak discharge data suggest the channel was likely abandoned between 1957 and 1964. Twelve sediment cores between 2 and 3 meters in depth were collected with a vibracore, and grain-size analyses of the cutoff channel substrate were compared to similar data collected from the modern channel. Results showed an historical fining-upward trend in the mean grain size of the coarse fraction, from gravel in the cutoff channel to sand in the modern channel, but no change in the mean grain size of the fine fraction. A series of alternative explanations were examined to elucidate this fining, including sediment storage, trends in population and crop cultivation, existence of BMPs, and sediment transport during floods. Evidence from this study strongly suggests that a shift from the cultivation of low-cover crops (hay and oats) to high-cover crops (corn and soybeans) has changed the proportion of coarse-grained to fine-grained sediment loading in this section of the Sandusky River. The results have implications both for the effectiveness of BMPs in Crawford County and possibly for Lake Erie sediment budgets.
  • Authors:
    • Mimikou, M.
    • Panagopoulos, I.
    • Kapetanaki, M.
  • Source: Journal of Soils and Sediments
  • Volume: 7
  • Issue: 4
  • Year: 2007
  • Summary: This study investigated the behaviour of two groups of widespread and different textured soil types, on nutrient (N, P) losses under cold climate conditions. The investigation was conducted in the Norwegian Vansj-Hoblv catchment through the application of a physical model named Soil and Water Assessment Tool (SWAT), taking into consideration the additional aspect of freezing soils during winter, which distinguishes Scandinavian from other European soils. SWAT is a physical river-basin model that was developed for the USDA Agricultural Research Service, by the Blackland Research Center in Texas. In the current modelling approach the catchment was divided into 43 Hydrologic Response Units (HRUs) which consist of different combinations of the existed land cover and soil types. Nutrient losses arising from these HRUs were estimated for the period 1990-2001 through the simultaneous simulation of water and sediment processes that are closely linked to the nutrient processes. The model took into account soil temperature to quantify water and nutrient transport to deeper layers, considering negligible downward movement when the soil temperature was under 0°C. It also simulated the aboveground development of the snowpack and the snowmelt processes on a daily basis. The six different soil types were aggregated in two groups according to their similarity in texture and other physical properties, one group of fine-textured soils and a group of coarse soils. The results were evaluated for different crop cultivations (barley, oats and wheat) of the aforementioned soils. Finally, the model was calibrated and validated by comparing predicted results with measured data. Fine-textured soils caused significant runoff, sediment and nutrient yields to the river system while coarser soils were characterized by high water drainage and nitrates leaching. The first soil group caused a mean of 517 mm of runoff in annual basis, 200 mm higher than this arising from coarse soils. Moreover, 3 tonnes of sediments per hectare, 24.6 kg N/ha and 0.54 kg P/ha were lost annually to surface water from fine soils while the average respective losses originating from coarse soils were only 1.3 tonnes of sediments/ha, 13.6 kg N/ha and 0.17 kg P/ha. The sensitivity ranking of the soil types to nutrient losses was silty-clay-loam > silty-loam > clay > loamy > sandy-loam > sandy. An average of 277 mm of water was percolated annually under the bottom of the soil profile in coarse soils causing the additional leaching of 5.6 kg N-NO 3/ha whereas the losses originating from fine-textured soils were 153 mm and 2.5 kg/ha, respectively. According to their sensitivity in nitrates leaching, the six soil types were ranked in the following order: sandy > loamy > sandy-loam > silty-loam > silty-clay-loam > clay. The results showed that even though under cold climate conditions, with monthly periods of average air-temperatures below zero, the overall amounts of annual TN and TP losses to surface waters as well as nitrates leaching to groundwater were considerable. The results demonstrate the need of considering the soil differentiation in Scandinavian countries similarly to the rest of Europe in order to apply mitigation measures against nutrient losses to surface and groundwater.
  • Authors:
    • Balkcom, K. S.
    • Gamble, B. E.
    • Patterson, M. G.
    • Reeves, D. W.
    • Price, A. J.
    • Arriaga, F. J.
    • Monks, C. D.
  • Source: Peanut Science
  • Volume: 34
  • Issue: 1
  • Year: 2007
  • Summary: Information is needed on the role of cover crops as a weed control alternative due to the increase in adoption of conservation-tillage in peanut production. Field experiments were conducted from autumn 1994 through autumn 1997 in Alabama to evaluate three winter cereal cover crops in a high-residue conservation-tillage peanut production system. Black oat ( Avena strigosa Schreb.), rye ( Secale cereale L.), and wheat ( Triticum aestivum L.) were evaluated for their weed-suppressive characteristics compared to a winter fallow system. Three herbicide systems were utilized: no herbicide, preemergence (PRE) herbicides followed by (fb) postemergence (POST) herbicides, and PRE fb sequential POST herbicides. The PRE fb POST herbicide input system consisted of pendimethalin at 1.12 kg ai/ha fb an additional early POST application of paraquat at 0.14 kg ai/ha plus bentazon at 0.56 kg ai/ha. The PRE fb sequential POST herbicide input system contained the aforementioned herbicides fb 2,4-DB at 0.22 kg ai/ha plus chlorimuron at 0.14 kg ai/ha applied late POST. No cover crop was effective in controlling weeds without a herbicide program. However, when black oat or rye was utilized with PRE fb POST herbicides, weed control was similar to the high input system in two out of three years. Yield increased in 14 of 27 comparisons following conservation-tilled peanut using the Brazilian cover crop management system, compared to a winter fallow system. Yields never decreased following a winter cover crop compared to winter fallow. The winter fallow, high herbicide input system yielded between 7 and 26% less peanut compared to the highest yielding system that included a winter cover crop. The Brazilian system using black oat or rye cover crop has potential to increase peanut productivity and reduce herbicide inputs for peanuts grown in the Southeast.
  • Authors:
    • Santen, E. van
    • Price, A.
    • Shaw, J. N.
    • Sullivan, D. G.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 6
  • Year: 2007
  • Summary: Conservation tillage is a commonly adopted best management practice for reducing runoff and erosion, and increasing infiltration. Yet current methodologies in place to monitor conservation tillage adoption are largely inappropriate for regional or national assessments. A major goal of this study was to evaluate the spectral response properties of four alternative winter cover crops using remotely derived crop residue cover indices. Experimental plots were located in east-central Alabama on a coarse-loamy siliceous, subactive, thermic Plinthic Paleudult. The experiment was a randomized complete block design having four replications of each of the following treatments: one fallow conventional tillage treatment and four no-tillage treatments with black oat ( Avena strigosa Schreb.), crimson clover ( Trifolium incarnatum L.), turnip ( Brassica rapa L. subsp.rapa), or rye ( Secale cereale L.) cover crops. Remotely sensed data were acquired three times using a 14 d sampling interval beginning near planting and using a handheld multispectral radiometer (485-1650 nm) in 2005 and 2006. Three crop residue cover indices using combinations of middle-infrared and visible spectra were compared and evaluated. Rye, clover, and black oat were spectrally similar, having an overall spectral response ranging from 8 to 45% (440-1650 nm). Increasing soil water content between remotely sensed data acquisitions was evidenced by as much as a 24% decline in middle-infrared reflectance. Despite this variability, a normalized difference ratio of middle-infrared (1650 nm) and blue (445 nm) spectra (Crop Residue Cover Index) provided the most consistent differentiation between tillage systems, varying within 8% of benchmark conditions (low soil water and low canopy cover). Considering the impact that conservation tillage may have on soil and water resources, rapid, watershed scale assessments of conservation tillage adoption may facilitate natural resource inventories, carbon sequestration estimates, and improved agricultural water management regimes.