• Authors:
    • Purcell, P. J.
    • O'Brien, M.
    • Boland, T. M.
    • O'Kiely, P.
    • O'Donovan, M.
  • Source: Animal Feed Science and Technology
  • Volume: 166/167
  • Year: 2011
  • Summary: This study determined in vitro rumen CH 4 production of perennial ryegrass grown within a well managed Irish dairy production system. Four strategies, consisting of two pre-grazing herbage mass (HM; high 2400 and low 1600 kg dry matter (DM)/ha) and two sward allowance (SA; high 20 and low 15 kg DM/cow/d) treatments, were compared throughout the grazing season using an in vitro rumen gas production technique. Samples were collected during five 22 d sampling periods (SP 1-5) throughout the growing season and analysed for in vitro rumen CH 4 output, and total gas and volatile fatty acid production following 24 h of incubation with rumen fluid and artificial saliva. High HM was associated with lower organic matter digestibility and crude protein concentration compared with low HM, whereas SA had no effect on herbage composition. Methane output as ml/g DM incubated or digested was higher (P<0.05) for the high HM treatment than for the low HM treatment (25.5 versus 24.6 and 32.2 versus 30.5, respectively). Sward allowance had no effect on CH 4 output, but CH 4 output/g DM incubated or digested was affected by sampling period. Sward allowance did not alter methanogenesis and, although HM affected CH 4 output in vitro, the biological scale of this effect was small. Thus, grass management strategy had little impact on in vitro rumen CH 4 output when herbage was consistently of high nutritional quality.
  • Authors:
    • Rao, S. C.
    • Northup, B. K.
  • Source: Crop Science
  • Volume: 51
  • Issue: 4
  • Year: 2011
  • Summary: Sources and methods of use of organic nitrogen (N) in the southern Great Plains (SGP) need testing to find alternatives to increasingly expensive inorganic fertilizer. We examined the function of grass pea ( Lathyrus sativus L.), a cool-season pulse, as a preplant N source for continuous, no-till winter wheat ( Triticum aestivum L.). The study was conducted in central Oklahoma (35degrees40′N, 98degrees00′W, elevation 414 masl) from 2004 to 2008, on three replicate blocks of four experimental plots (6 by 10 m). Inoculated grass pea seed ('AC-Greenfix') was sown during late summer fallow (mid-August) in one randomly chosen plot per block (75 kg ha -1, 60-cm rows; 75% germination). Three additional plots per block mimicked summer fallow with 0 (control), 40, or 80 kg N ha -1 inorganic fertilizer applied. All treatments were repeated on the same plots throughout the study. Samples were collected from grass pea plots at flowering in early October to define aboveground biomass and analyzed for N concentration and digestibility. Aboveground biomass of grass pea was shredded with a flail mower and left on the soil surface, fertilizer treatments were applied, and wheat ('Jagger') was sown (100 kg ha -1, 20-cm rows). Aboveground wheat biomass was collected at three growth stages (elongation, flowering, physiological maturity) and analyzed for N concentration. Grass pea aboveground biomass contained enough N to meet the needs of wheat at planting in only 1 yr. Wheat biomass and amounts of N in wheat aboveground biomass in response to grass pea were intermediate between the 0 and 40 kg applied N ha -1, as was yield and N accumulated in wheat grain. Therefore, grass pea was not effective as a preplant source of N for continuous no-till winter wheat in the SGP. Additional research is required to define factors that limit the function of grass pea as a source of N for continuous no-till winter wheat and its potential function in other crop rotations.
  • Authors:
    • Corbeels, M.
    • Rufino, M. C.
    • Nyamangara, J.
    • Giller, K. E.
    • Rusinamhodzi, L.
    • van Wijk, M. T.
  • Source: Agronomy for Sustainable Development
  • Volume: 31
  • Issue: 4
  • Year: 2011
  • Summary: Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact.
  • Authors:
    • Ryan, J.
    • Kapur, S.
    • Ibrikci, H.
    • Singh, M.
  • Source: Journal of Sustainable Agriculture
  • Volume: 35
  • Issue: 6
  • Year: 2011
  • Summary: As most of the organic carbon (C) in the biosphere resides in the soil in the form of soil organic matter (SOM), tillage practices can potentially increase C losses to the atmosphere as carbon dioxide, thus contributing to greenhouse gases that exacerbate climate change. In the past century, conventional tillage, involving plowing and secondary cultivation, has unwittingly decreased C stocks in arable soils in North America, Europe, and Australia. The information on the effects of tillage on soil C and related properties in the Mediterranean region is scant, with evidence of resilience being even rarer. While long-term trials that directly measure tillage effects are rare in the Mediterranean, the alternative is a retrospective based on soil management history. In this study of a Vertisol in southern Turkey, we sampled sections of a field that had been intensively cultivated for about 20 years and 40 years, as well as a section left undisturbed in native vegetation for 14 years following years of conventional tillage. The SOM and total nitrogen (N) values were inversely related to cultivation intensity or duration, while the highest values were from the uncultivated site. Labile biomass C and N values followed the same trends with cultivation, whereas available P increased with cultivation time; in contrast, the percentage of water-stable aggregates decreased with cultivation duration. The study showed that such clay soils show a high degree of resilience and can recover in a relatively short time period if left uncultivated or in fallow. While preservation or set aside of arable crop land is not a viable option for farmers, reducing tillage intensity is feasible. The study suggests that minimum tillage or no-till could promote resilience and mitigate the adverse soil effects of conventional tillage that have already occurred.
  • Authors:
    • Jones, B. P.
    • Sequeira, C. H.
    • Alley, M. M.
  • Source: Soil Biology and Biochemistry
  • Volume: 43
  • Issue: 2
  • Year: 2011
  • Summary: Particulate organic matter (POM) and light fraction (LF) organic matter are potentially labile (active) fractions of soil organic matter (SOM) that have been shown to be indicators of short-term changes in soil management practices (e.g. tillage, manure and fertilizer applications, and crop rotation). These two fractions consist mainly of partially decomposed plant residues, microbial residues, seeds, and spores forming organo-mineral complexes with soil mineral particles; however, they cannot be used as synonyms because of their different chemical composition and structure. Particulate-OM is recovered by size-based procedures while LF is generally recovered in two distinct fractions [free-LF (FLF) and occluded-LF (OLF)] using density-based solutions in conjunction with soil-aggregate disruption. Solutions used in these density-based separations have most commonly varied in density from 1.6 to 2.0 g cm -3. Sodium iodide (NaI) and sodium polytungstate (SPT) are the chemicals most often used to prepare the density solutions in LF recovery but comparisons of the effectiveness of two solutions have not been conducted. The objectives of this research were: (1) compare the efficiency of similar density solutions of NaI and SPT in recovering FLF; and (2) compare POM, FLF, and OLF as possible sensitive indices of short-term soil changes due to tillage management. Soil samples were collected at 0-15 cm depth from a cropping system experiment conducted on a silt loam Ultisol. Plots selected for sampling had received either reduced till (RT) or no-till (NT), and cropping was continuous corn silage for a period of 3 years prior to sampling. Solutions of NaI and SPT at densities of 1.6 and 1.8 g cm -3 were used to recover FLF, and OLF was recovered with SPT solution at a density of 2.0 g cm -3 from the soil pellet remaining after FLF recovery with SPT 1.6 g cm -3. The average total soil organic carbon (SOC) content of these samples was of 12.7 g kg -1, and carbon-POM (C-POM), carbon-FLF (C-FLF), and carbon-OLF (C-OLF) represented 22.4, 5.5, and 5.2% of it, respectively. In general, C-FLF and nitrogen-FLF (N-FLF) contents recovered did not differ significantly between chemical solutions (NaI or SPT) adjusted to the same density (1.6 or 1.8 g cm -3). Increasing the density within a specific solution (NaI or SPT) resulted in significantly higher C-FLF and N-FLF recovery. For instance, C-FLF recovery averaged 637 and 954 mg kg -1 at 1.6 and 1.8 g cm -3, respectively. For both chemicals increasing density from 1.6 to 1.8 g cm -3 reduced the variability in recovering C-FLF and N-FLF with coefficient of variation values decreasing from a range of 14.9-19.1% for densities of 1.6 g cm -3 to 6.7-10.4% when densities increased to 1.8 g cm -3. In the present work, POM and OLF were more sensitive than FLF to changes in tillage management, with significantly greater amounts of the sensitive fractions in RT samples. A better sensitivity of FLF would be expected if treatments dealing with residue input (e.g. crop rotation and cover crop) were evaluated.
  • Authors:
    • Sequeira, C. H.
    • Alley, M. M.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 5
  • Year: 2011
  • Summary: Soil organic matter (SOM) is commonly used as an indicator of soil quality, with different fractions being used as indices to measure changes in SOM caused by management. The objective of this study was to compare whether selected SOM fractions exhibited sensitivity to short-term changes in management. The experiment was conducted for similar to 3 yr as a split-split-plot design with crop rotation as the whole-plot treatment factor, tillage as the subplot treatment factor, and cover crop management as the sub-subplot treatment factor. Soil samples were collected at the 0- to 15-cm depth. Soil organic C (SOC) and N, particulate organic matter (POM), free light fraction (FLF), Illinois soil N test (ISNT), and easily oxidizable C (EOC) were tested as possible sensitive indices to changes in management. The stable fraction SOC was only affected by cover crop management, while C and N contents and C/N ratio of the labile POM and FLF fractions were affected by additional management practices. Between POM and FLF, the latter was the most sensitive, with cover crop management having the greatest effect. Because FLF is chemically and structurally closer to plant residues than POM, the sensitivity rank position of these fractions would probably be at least more similar if only tillage management was considered. In addition, the lack of sensitivity of ISNT and EOC to any tested management practice is added to previous studies that have raised questions of the representation of the labile SOM pool through these fractions.
  • Authors:
    • Singh, R.
    • Sharma, A. R.
    • Dhyani, S. K.
    • Dube, R. K.
  • Source: Journal of Crop Improvement
  • Volume: 25
  • Issue: 4
  • Year: 2011
  • Summary: Mulching is highly beneficial for resource conservation under rainfed conditions, but non-availability of organic biomass and easy availability of fertilizers and herbicides has led to a gradual discontinuation of this practice. Various vegetative materials, including some troublesome weedy perennials, are available locally, which can be recycled for enhanced soil moisture and nutrient conservation. A field experiment was conducted at Dehradun, India, from 2001-2004 to study the effect of mulching with kudzu ( Peuraria hirsuta), wild sage ( Lantana camara), and subabul ( Leucaena leucocephala) applied at 30 and 60 days of growth of maize ( Zea mays), maize harvest, and sowing of wheat ( Triticum aestivum). Application of 10 t/ha (fresh biomass) added 1.6-2.3 t dry matter through Peuraria, 2.5-3-2 t through Lantana, and 2.9-3-9 t/ha through Leuceana, which contributed 47.7-60.9 kg N, 58.4-70.9 kg N, and 118.4-148.4 kg N/ha, respectively. All mulching materials were beneficial and improved productivity of maize significantly by 16.6-20.6% over no mulching. Wheat yield also increased because of mulching in previous maize (+11.2%), and the beneficial effect was relatively greater (12.4-25.1%) when mulching was done at maize harvest or wheat sowing. Mulching showed improvement in organic C and total N status, and a decrease in bulk density associated with an increase in infiltration rate across three cropping cycles. Wheat gave three to five times more net profit than maize, and the net benefit-cost ratio of the system was the highest (1.34-1.35) when mulching was done at 60 days of maize growth with Peuraria and Leucaena. It was concluded that mulching with available vegetative materials in standing crop of maize or after harvest was beneficial for improving moisture conservation, productivity, and profitability of a maize-wheat cropping system under Doon valley conditions.
  • Authors:
    • Maul, J. E.
    • Meisinger, J. J.
    • Cavigelli, M. A.
    • Spargo, J. T.
    • Mirsky, S. B.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 90
  • Issue: 2
  • Year: 2011
  • Summary: Sustainable soil fertility management depends on long-term integrated strategies that build and maintain soil organic matter and mineralizable soil N levels. These strategies increase the portion of crop N needs met by soil N and reduce dependence on external N inputs required for crop production. To better understand the impact of management on soil N dynamics, we conducted field and laboratory research on five diverse management systems at a long-term study in Maryland, the USDA- Agricultural Research Service Beltsville Farming Systems Project (FSP). The FSP is comprised of a conventional no-till corn ( Zea mays L.)-soybean ( Glycine max L.)-wheat ( Triticum aestivum L.)/double-crop soybean rotation (NT), a conventional chisel-till corn-soybean-wheat/soybean rotation (CT), a 2 year organic corn-soybean rotation (Org2), a 3 year organic corn-soybean-wheat rotation (Org3), and a 6 year organic corn-soybean-wheat-alfalfa ( Medicago sativa L.) (3 years) rotation (Org6). We found that total potentially mineralizable N in organic systems (average 315 kg N ha -1) was significantly greater than the conventional systems (average 235 kg N ha -1). Particulate organic matter (POM)-C and -N also tended to be greater in organic than conventional cropping systems. Average corn yield and N uptake from unamended (minus N) field microplots were 40 and 48%, respectively, greater in organic than conventional grain cropping systems. Among the three organic systems, all measures of N availability tended to increase with increasing frequency of manure application and crop rotation length (Org2 < Org3 ≤ Org6) while most measures were similar between NT and CT. Our results demonstrate that organic soil fertility management increases soil N availability by increasing labile soil organic matter. Relatively high levels of mineralizable soil N must be considered when developing soil fertility management plans for organic systems.
  • Authors:
    • Stavi,I.
    • Lal,R.
    • Owens,L. B.
  • Source: Agronomy for Sustainable Development
  • Volume: 31
  • Issue: 3
  • Year: 2011
  • Summary: Contrary to earlier studies, this study suggests that even one year of tillage within a long-term no-till agroecosystem adversely affected the soil quality, with possible negative impact on crop yields. Worldwide interest in conservation tillage is increasing, because conventional tillage adversely impacts the long-term quality of the soil and its vulnerability to erosion. No-till agriculture minimizes adverse impacts of an intensive arable land use. In some cases, occasional tillage is used as a means of weed or pathogen control. Therefore, this study was conducted in eastern Ohio to examine soil quality as affected by occasional tillage, i.e. disk plowed every 3-4 years, within a long-term no-till agroecosystem. The study compared the soil characteristics between two fields, both under corn ( Zea mays L.) at the time of the study. Soil properties were studied for three depths of 0-6, 6-12, and 12-18 cm. Compared with the continuous no-till field, the field under occasional tillage had significantly higher bulk density of 1.45 versus 1.31 gcm -3, and somewhat higher soil penetration resistance of 1.77 versus 1.56 MPa. Also, compared with the no-till field, the field under occasional tillage had significantly lower water stable aggregate of 475 versus 834 gkg -1, mean weight diameter of 1.4 versus 3.4 mm, field moisture capacity of 293 versus 360 gkg -1, equilibrium infiltration rate of 2.0 versus 6.7 mm min -1, and cumulative infiltration of 353.4 versus 1,211.8 mm. The field under occasional tillage had somewhat lower soil organic carbon of 16.0 versus 19.2 gkg -1, soil water sorptivity of 16.3 versus 36.5 mm min -0.5, and transmissivity of 2.1 versus 4.9 mm min -1. The occasional tillage had no effect on the soil shear strength. In general, the effect of tillage on soil properties decreased with increase in soil depth. Also corn yields were compared between the two agroecosystems. Compared with the no-till field, the field under occasional tillage had significantly lower grain moisture content of 22.4 versus 28.2%, and somewhat lower wet stover biomass of 14.6 versus 20.2 Mg ha -1, wet corn ear yield of 10.0 versus 11.4 Mg ha -1, and dry grain yield of 8.2 versus 9.4 Mg ha -1. As contrasted with earlier studies which were conducted under controlled research plots, this study was conducted under on-farm conditions.
  • Authors:
    • Sirrine, J. R.
    • Simonson, P.
    • Hoagland, L. A.
    • Darby, H.
    • Benedict, C. A.
    • Turner, S. F.
    • Murphy, K. M.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 6
  • Year: 2011
  • Summary: Hop cones grown on the female plant of the perennial crop ( Humulus lupulus L.) are an integral component of the brewing process and provide flavor, bitterness, aroma, and antimicrobial properties to beer. Demand for organically grown hops from consumers via the brewing industry is on the rise; however, due to high N requirements and severe disease, weed, and arthropod pressures, hops are an extremely difficult crop to grow organically. Currently, the majority of the world's organic hops are grown in New Zealand, while other countries, including China, are beginning to increase organic hop production. Land under organic hop production in Washington State, where 75% of the hops in the United States are grown, increased from 1.6 ha to more than 26 ha from 2004 to 2010, and other hop-producing states demonstrate a similar trend. Removing hops from the USDA Organic Exemption list in January 2013 is expected to greatly increase organic hop demand and will require corresponding increases in organic hop hectarage. Current challenges, including weed management, fertility and irrigation management, insect and disease pressures, and novel practices that address these issues will be presented. Here, we discuss current and future research that will potentially impact organic hop production in the United States.