• Authors:
    • Kussman, R. D.
    • Kremer, R. J.
  • Source: Agroforestry Systems
  • Volume: 83
  • Issue: 2
  • Year: 2011
  • Summary: Intercropping alleys in agroforestry provides an income source until the tree crop produces harvestable yields. However, cultivation of annual crops decreases soil organic matter and increases soil erosion potential, especially on sloping landscapes. Perennial crops maintain a continuous soil cover, increase water infiltration, reduce soil erosion, and improve overall soil quality. The objective of this on-farm study was to assess the effects of a perennial legume, kura clover ( Trifolium ambiguum M. Bieb.), on soil quality in a recently established pecan ( Carya illinoinensis Wangenh. C. Koch) orchard. The pecan-kura clover agroforestry practice was established on deep loess soils of the Missouri River hills landscape. These silt loams are on 2-20% slopes and can be highly erosive. Kura clover, introduced as the alley crop 5 years after pecan planting, was selected based on its perennial growth habit, nitrogen-fixing ability, winter hardiness, high forage quality, and soil conservation properties. Kura clover was seeded in 2001 and harvested for hay annually beginning 2003. Soil quality indicators of total organic C, total N, water-stable aggregates, and selected soil enzymes were determined on surface soil samples collected annually after kura clover establishment. Soil organic C and activities of soil enzymes increased compared with cultivated and grass pasture control soils by the eighth year of establishment. Water-stable aggregation improved by 50% and surface soil shear strength improved significantly ( P<0.05) in alleys compared with control sites. Results illustrate that kura clover as the alley-cropped component improved soil fertility and biological activity through increased organic matter and improved soil structure, and yielded high quality forage valuable for the cattle-feeding operation. Kura clover maintained or improved soil quality, reduced soil erosion potential, and benefited pecan growth by providing a source of soil nitrogen and improving soil structure for adequate water infiltration and aeration.
  • Authors:
    • Liu, K.
    • Wiatrak, P.
  • Source: International Journal of Plant Production
  • Volume: 5
  • Issue: 4
  • Year: 2011
  • Summary: Nitrogen (N) application management needs to be refined for low yielding environments under dryland conditions. This 3-yr study examined nitrogen fertilization management effects on corn ( Zea mays L.) plant characteristics and grain yield in rain fed environment under conventional tillage system. Nitrogen fertilization management consisted of two timing methods of N application [all N at planting and as split with 35 kg N ha -1 applied at planting and remaining N applied at vegetative (V) 6 growth stage] and five N rates (0, 45, 90, 135, and 180 kg N ha -1). Insufficient rainfall at reproductive stage in 2008 and 2009 likely resulted in significant reduction of grain yield compared with grain yield in 2007, average 2.9 vs. 5.9 Mg ha -1. Grain yield increased with N application up to 45 kg ha -1; however, no further increase in N application resulted in increased yields. Plant height, ear height, relative chlorophyll (SPAD) content, and normalized difference vegetation index (NDVI) at reproductive (R 1) stage increased with increasing N rate up to 90, 90, 135, and 90 kg N ha -1, respectively. Corn grain yield significantly correlated with plant height at R 1, SPAD at V 8, NDVI and LAI at V 8 and R 1 stage. The combination of plant height, NDVI, and LAI of R 1 stage explained most of the variability of grain yield (r-square=0.71). The fertilization timing had no effect on corn grain yield and plant characteristics. These observations showed that applying more than 45 kg N ha -1 to corn under dryland conditions with insufficient rainfall, especially during corn pollination, may not significantly increase grain yields.
  • Authors:
    • Figueiredo, G. C.
    • Medeiros, J. C.
    • Giarola, N. F. B.
    • Fracetto, F. J. C.
    • Silva, A. P. da
    • Cerri, C. E. P.
  • Source: Plant Soil
  • Volume: 338
  • Issue: 1-2
  • Year: 2011
  • Summary: The decomposition rate of soil organic matter (SOM) is affected by soil management practices and particularly by the physical and hydraulic attributes of the soil. Previous studies have indicated that the SOM decomposition is influenced by the Least Limiting Water Range (LLWR). Therefore, the objective of this study was to relate the C-CO 2 emissions to the LLWR of the surficial layer of soil under two management systems: no-tillage (NT), conducted for 20 years, and conventional tillage (CT). Soil in NT presented greater soil organic carbon (SOC) stocks than in CT. Emissions of C-CO 2 were greater in the NT than in the CT, because of the greater carbon stocks in the soil surface layer and the greater biological activity (due to the improvement of the soil structure) in NT as compared to CT. The use of LLWR associated with the measurement of C-CO 2 emissions from the soil could help to predict the efficacy of the adopted management system for trapping carbon in the soil.
  • Authors:
    • Singh, M. R.
    • Singh, M. K.
  • Source: Indian Journal of Agronomy
  • Volume: 56
  • Issue: 2
  • Year: 2011
  • Summary: Excessive tillage and soil degradation are important factors limiting wheat [ Triticum aestivum (L) emend. Fiori & Paol.] productivity, particularly in rice ( Oryza sativa L.) - wheat cropping system. Therefore present field experiment was conducted during winter of 2007-08 and 2008-09 at Varanasi to study the effect of seed rate and weed management on weed growth and yield in late sown zero till wheat. Treatments comprised of three seed rates viz., 100, 120 and 140 kg/ha in the main plots and five weed management treatments viz., weedy, 2,4-D Na salt 625 g/ha (POE), metsulfuron methyl 4 g/ha (POE), sulfosulfuron 30 g/ha+metsulfuron methyl 2 g/ha (POE) and 2-hand weedings in sub-plots with three replications. Broad leaved weed population was found more in the experimental crop as compared to narrow leaved weeds. All the herbicidal treatments were effective in reducing weed density and dry weight in comparison to weedy check. Seed rate of 120 kg/ha recorded significantly higher grain yield in comparison to seed rate of 100 and 140 kg/ha. Amongst weed management treatments all the herbicidal weed control had significantly higher grain yield in comparison to weedy check. Sulfosulfuron 30 g/ha+metsulfuron methyl 2 g/ha had higher grain yield than alone application of 2, 4-D @ 625 g/ha and metsulfuron methyl 4 g/ha.
  • Authors:
    • Wood,C. W.
    • Price,A. J.
    • Mulvaney,M. J.
  • Source: Journal of Sustainable Agriculture
  • Volume: 35
  • Issue: 3
  • Year: 2011
  • Summary: Limited input producers may adopt no-till production if sufficient weed suppression can be achieved. High-biomass producing cover crops used in conjunction with organic mulches may provide sufficient weed control in no-till vegetable production. Our objective was to quantify weed suppression from a forage soybean summer cover crop and three types of organic mulches applied after collard ( Brassica oleracea L.) planting. Forage soybean residue did not suppress weeds, but mulches were generally effective. Broadleaf and sedge weeds decreased in population size over the three-year period, but grass weed management remained problematic until three years after conversion to no-till. Grass suppression was greater when mulches were applied after the first year. Collard yield, averaging 17,863 kg ha -1, was not affected by any cover crop or mulch treatment.
  • Authors:
    • Ortega, A. L.
  • Source: Archives of Agronomy and Soil Science
  • Volume: 57
  • Issue: 6
  • Year: 2011
  • Summary: The permanent bed planting system for wheat ( Triticum aestivum L.) production has recently received additional attention. Studies using hard red spring wheat (cultivar Nahuatl F2000) were conducted at two locations in central Mexico. The studies included the installation of three furrow diking treatments, two granular N timing treatments and three foliar N rates applied at the end of anthesis. The objective was to evaluate the effect of these factors on wheat grain yield, yield components and grain N in a wheat-maize ( Zea maize L.) rotation with residues of both crops left as stubble. Results indicated that diking in alternate furrows increased both grain yield and the final number of spikes per m 2. The split application of N fertilizer enhanced the number of spikes per m 2 and grain N uptake, but the effect on grain yield was inconsistent. Similarly, grain protein increased with the foliar application of 6 kg N ha -1, depending upon the maximum temperature within the 10 days following anthesis. The normalized difference vegetative index (NDVI) readings collected at four growth stages were generally higher for the split N application than for the basal N application at planting. Grain N uptake was associated to NDVI readings collected after anthesis.
  • Authors:
    • Parr, M.
    • Grossman, J. M.
    • Reberg-Horton, S. C.
    • Brinton, C.
    • Crozier, C.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 6
  • Year: 2011
  • Summary: Sixteen winter annual cover crop cultivars were grown in North Carolina to determine total N accumulation, biological N fixation (BNF) potential, and compatibility with a roller-crimper-terminated organic corn ( Zea mays L.) production system. Cover crops and termination dates were tested in a stripped block design. Treatments included hairy vetch ( Vicia villosa Roth), common vetch ( Vicia sativa L.), crimson clover ( Trifolium incarnatum L.), Austrian winter pea ( Pisum sativum L.), berseem clover ( Trifolium alexandrinum L.), subterranean clover ( Trifolium subterraneum L.), narrow leaf lupin ( Lupinus angustifolius L.), and Balansa clover ( Trifolium michelianum Savi.), as well as bicultures of rye ( Secale cereale L.), hairy vetch, and Austrian winter pea. Roller-crimper termination occurred in mid-April, early May, and mid-May. Total biomass, N concentration, and C/N ratios were determined for cover crops at all roll times and natural 15N abundance at the optimal kill date. Hairy vetch and crimson clover monocultures had the greatest overall biomass in 2009, and bicultures the greatest biomass in 2010. Crimson clover successfully terminated in late April, hairy vetch and Austrian winter pea in mid-May, and berseem clover and common vetch in late May. All cover crops except lupin and subterranean clover derived between 70 and 100% of their N from the atmosphere. Corn response to cover crop mulches was significantly affected by the time of rolling, with poor stands resulting from competition with insufficiently terminated mulches. Crimson, Balansa, and subterranean clover mulches resulted in poor corn yields despite relatively high levels of total N. The highest corn yields were achieved in hairy vetch and rye plus hairy vetch bicultures.
  • Authors:
    • Paudel, B. R.
    • Anderson, S. H.
    • Udawatta, R. P.
  • Source: Applied Soil Ecology
  • Volume: 48
  • Issue: 2
  • Year: 2011
  • Summary: Establishment of buffers and incorporation of trees and shrubs are believed to improve soil quality and thereby improve water quality from grazed pasture systems. Although enzyme activities and water stable aggregates have been identified as measurable soil quality parameters for early responses to changes in soil management, the literature lacks information on those parameters for grazing systems with agroforestry buffers. The objective of this study was to examine the activities of fluorescein diacetate (FDA) hydrolase, dehydrogenase, beta-glucosidase and beta-glucosaminidase, the percentage of water stable aggregates (WSA) and soil organic carbon and nitrogen as soil quality parameters for grazed pasture and row-crop systems. The study consisted of four management treatments: grazed pasture (GP), agroforestry buffer (AgB), grass buffer (GB) and row-crop (RC). The WSA was determined by wet sieving method while the enzyme activities were colorimetrically quantified using a spectrophotometer in laboratory assays. Soil organic carbon (SOC) and total nitrogen (TN) contents were also determined. Two soil depths (0-10 and 10-20 cm) were analyzed for all treatments. The row-crop treatment showed significantly lower activities compared to all other treatments for beta-glucosidase and beta-glucosaminidase enzymes along with lower WSA. The dehydrogenase activities were significantly higher in GP treatment compared to RC treatment. The FDA hydrolase activities were not significantly different among treatments. Surface soil revealed higher enzyme activities and higher WSA than the sub-surface soil. The treatment by depth interaction was significant for beta-glucosidase and beta-glucosaminidase enzymes. The soil organic carbon and total nitrogen data strongly supported the results of enzyme activities and WSA. Implications can be made that perennial vegetation enhances organic matter accumulation in the soil, has minimum disturbance to the soil and will have positive impacts on the ecosystem.
  • Authors:
    • Pes, L. Z.
    • Amado, T. J. C.
    • La Scala Jr., N.
    • Bayer, C.
    • Fiorin, J. E.
  • Source: Soil & Tillage Research
  • Volume: 117
  • Year: 2011
  • Summary: The physical protection of mineralizable carbon (C) in aggregates has been identified as the primary mechanism of soil C stabilization. Therefore, it is possible to hypothesize that the disruption of aggregate by soil tillage is a key process driving C losses during the crop-establishment period. However, these findings are based on studies performed in temperate soils. Limited information is available for studies performed in subtropical and tropical soils, especially in Oxisols, which are rich in oxides that provides chemical C stabilization. This study was performed in southern Brazil in a long-term soil-management experiment carried out in a clay Typic Haplorthox in Cruz Alta (RS). During the 22nd year of the experiment, carbon dioxide (CO2-C) emissions, temperature, and soil moisture were intensively evaluated over a 21-day summer crop-establishment period using a closed infrared CO2-flux chamber. The cropping system investigated was an intensive crop rotation following the soil input of winter-cover crops (black oat (Avena strigosa Schreb) + common vetch (Vicia sativa L) under two contrasting tillage systems, conventional tillage (CT) and no-till (NT). The apparent contributions to CO2-C losses by resident soil C associated with aggregate disruption and recent crop-residue C input were assessed in treatments with crop-residue input (+R) and with crop-residue removed (-R). An exponential-decay model was used to fit the differences in CO2-C flux between CT - R and NT - R (apparent aggregate-disruption effect) and between CT + R and CT - R (apparent recent crop-residue C input effect). As expected, the CT + R showed an increase of 72% in CO2-C losses relative to NT + R. During the three-week crop-establishment period, crop-residue C input was the primary source of CO2-C emissions under CT. The CO2-C losses under CT were equivalent to 65% of the aboveground C input by winter cover crops, whereas this value decreased to 35% in NT. Exponential-decay modeling of the data for the first week showed that approximately 20% of the CO2-C losses under CT were related to the exposure of mineralizable resident soil C due by tillage operations. The analysis showed that this value decreased to only 2% for the three-week period. The CO2-C emissions exhibited a positive linear relationship with soil temperature and soil water-filled porosity under NT, but a similar relationship was found only with soil temperature under CT. For this Oxisol during the crop-establishment period, the physical aggregate disruption induced by long-term CT played a secondary role in CO2-C losses relative to the recent crop-residue C input from tillage operations.
  • 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.