• Authors:
    • Singh, K.
    • Nandita, G.
    • Sonu, S.
  • Source: Experimental Agriculture
  • Volume: 43
  • Issue: 2
  • Year: 2007
  • Summary: A two-year study was undertaken in a tropical dryland agro-ecosystem to evaluate the effect of the application of soil amendments with contrasting chemical natures on crop productivity, grain yield, N-uptake and N-use efficiencies. The treatments involved the addition of equivalent amounts of N (80 kg N ha -1) through chemical fertilizer and three organic inputs at the beginning of the annual cycle: Sesbania aculeata shoots (high quality, C/N 16), wheat straw (low quality, C/N 82) and Sesbania+wheat straw (high and low quality combined, C/N 47), together with a control treatment. Test crops consisted of an annual sequence of rice and barley, sown in the rainy and winter seasons, respectively. Fertilizer and Sesbania inputs resulted in higher total net productivity (TNP) for the rice crop (47% and 32% increases over the control, respectively) than the combined (+28%) and wheat straw treatments (+10%). During the succeeding barley crop, maximum TNP was recorded in the Sesbania+wheat straw treatment (+52%), followed by wheat straw (+43%), fertilizer (+19%) and Sesbania (+17%). The TNP and grain yields of both crops added together were higher in Sesbania+wheat straw and fertilizer treatments compared to a single applications of either Sesbania or wheat straw. The Sesbania+wheat straw and fertilizer treatments resulted in more efficient utilization of N compared to the other treatments. Crop roots played a pivotal role in N-recovery from the soil and their N concentrations differed significantly ( p
  • Authors:
    • Singh, K.
    • Nandita, G.
    • Sonu, S.
  • Source: Soil Biology & Biochemistry
  • Volume: 39
  • Issue: 1
  • Year: 2007
  • Summary: The influence of exogenous organic inputs on soil microbial biomass dynamics and crop root biomass was studied through two annual cycles in rice-barley rotation in a tropical dryland agroecosystem. The treatments involved addition of equivalent amount of N (80 kg N ha -1) through chemical fertilizer and three organic inputs at the beginning of each annual cycle: Sesbania shoot (high-quality resource, C:N 16, lignin:N 3.2, polyphenol+lignin:N 4.2), wheat straw (low-quality resource, C:N 82, lignin:N 34.8, polyphenol+lignin:N 36.8) and Sesbania+wheat straw (high-and low-quality resources combined), besides control. The decomposition rates of various inputs and crop roots were determined in field conditions by mass loss method. Sesbania (decay constant, k=0.028) decomposed much faster than wheat straw ( k=0.0025); decomposition rate of Sesbania+wheat straw was twice as fast compared to wheat straw. On average, soil microbial biomass levels were: rice period, Sesbania ≥ Sesbania+wheat straw > wheat straw ≥ fertilizer; barley period, Sesbania+wheat straw > Sesbania ≥ wheat straw ≥ fertilizer; summer fallow, Sesbania+wheat straw > Sesbania > wheat straw ≥ fertilizer. Soil microbial biomass increased through rice and barley crop periods to summer fallow; however, in Sesbania shoot application a strong peak was obtained during rice crop period. In both crops soil microbial biomass C and N decreased distinctly from seedling to grain-forming stages, and then increased to the maximum at crop maturity. Crop roots, however, showed reverse trend through the cropping period, suggesting strong competition between microbial biomass and crop roots for available nutrients. It is concluded that both resource quality and crop roots had distinct effect on soil microbial biomass and combined application of Sesbania shoot and wheat straw was most effective in sustained build up of microbial biomass through the annual cycle.
  • Authors:
    • Lupwayi, N.
    • Haq, A.
    • Arshad, M.
    • Soon, Y.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1/2
  • Year: 2007
  • Summary: Information on which management practices can enhance soil organic matter (SOM) content and quality can be useful for developing sustainable crop production systems. We tested the influence of 12 years of no-till (NT) versus conventional tillage (CT), and four crop sequences on the organic C pools of a Grey Luvisolic sandy loam soil in northwestern Alberta, Canada. The crop sequences were: continuous wheat ( Triticum aestivum L.), field pea ( Pisum sativum L.)-wheat-canola ( Brassica rapa L.)-wheat, red clover ( Trifolium pratense L.) green manure-wheat-canola-wheat/red clover and fallow-wheat-canola-wheat. Soil samples from 1992, when the study was initiated, and 1996, 2000 and 2004 were analysed for total organic C (TOC), the light fraction (LF) and its C content, and water-soluble and mineralizable C. Total organic C in the top 15 cm of soil was higher in the red clover rotation than either the pea or fallow rotation by 1996. The tillage effect became significant only in 2004 with NT having a higher TOC than CT. The LF dry matter (DM) increased from 6.9 g kg -1 soil in 1992 to a range of 10-13 g kg -1 in 2000 and 2004. It was higher under NT than CT in 2 of 3 years and in the red clover rotation than the pea or fallow rotation in 1 of 3 years. The LF C content exhibited a similar trend as LF DM. The water-soluble and mineralizable C pools were not affected by tillage but decreased with time. Among crop rotations, the red clover rotation tended to result in higher levels of hot water-soluble and mineralizable C. It is concluded that tillage had a greater influence than crop rotation on the LF DM and LF C (as indicators of C storage), whereas the converse effect applied to mineralizable C and, to a lesser degree, hot water-soluble C (as indicators of SOM quality).
  • Authors:
    • Pals, A.
    • De Baets, S.
    • Galindo-Morales, P.
    • Poesen, J.
    • Knapen, A.
  • Source: Earth Surface Processes and Landforms
  • Volume: 32
  • Issue: 12
  • Year: 2007
  • Summary: Several studies illustrate the wind and water erosion-reducing potential of semi-permanent microbiotic soil crusts in arid and semi-arid desert environments. In contrast, little is hitherto known on these biological crusts on cropland soils in temperate environments where they are annually destroyed by tillage and quickly regenerate thereafter. This study attempts to fill the research gap through (a) a field survey assessing the occurrence of biological soil crusts on loess-derived soils in central Belgium in space and time and (b) laboratory flume (2 m long) experiments simulating concentrated runoff on undisturbed topsoil samples (0.4 x 0.1 m(2)) quantifying the microbiotic crust effect on soil erosion rates. Three stages of microbiotic crust development on cropland soils are distinguished: (1) development of a non-biological surface seal by raindrop impact, (2) colonization of the soil by algae and gradual development of a continuous algal mat and (3) establishment of a well-developed microbiotic crust with moss plants as the dominant life-form. As the silt loam soils in the study area seal quickly after tillage, microbiotic soil crusts are more or less present during a large part of the year under maize, sugar beet and wheat, representing the main cropland area. On average, the early-successional algae-dominated crusts of stage 2 reduce soil detachment rates by 37%, whereas the well-developed moss mat of stage 3 causes an average reduction of 79%. Relative soil detachment rates of soil surfaces with microbiotic crusts compared with bare sealed soil surfaces are shown to decrease exponentially with increasing microbiotic cover (b = 0 center dot 024 for moss-dominated and b = 0 center dot 006 for algae-dominated crusts). In addition to ground surface cover by vegetation and crop residues, microbiotic crust occurrence can therefore not be neglected when modelling small-scale spatial and temporal variations in soil loss by concentrated flow erosion on cropland soils in temperate environments. Copyright (C) 2007 John Wiley & Sons, Ltd.
  • Authors:
    • Kruzhkov, N. K.
  • Source: Kormoproizvodstvo
  • Issue: 10
  • Year: 2007
  • Summary: In trials in Orel province, Russia, in 1986-89, catch crops of spring rape were sown immediately after harvesting of winter wheat and barley crops in the following rotations: (1) vetch + oat mixture - winter wheat - barley - oats; (2) peas - winter wheat - maize - barley; (3) clover - winter wheat - potatoes - barley - oats undersown with clover; and (4) fallow - winter wheat - potatoes - buckwheat - barley. The rape was harvested for fodder or ploughed in as a green manure prior to the subsequent crop being sown. Green matter yields of 16-23.4 t/ha were obtained from the rape depending on sowing date and weather conditions. Results showed that after rape was harvested for fodder, yields of subsequent crops were reduced, significantly so in some cases (by 12% for the vetch + oats mixture, by 9.5% for potatoes and by 8.1% for silage maize). However, if the rape was ploughed in as a green manure, the yield of subsequent crops increased; for example, by 8.8% in barley, 9.7% in maize and 10.5% in peas. In terms of fodder units produced per ha, in all cases rape as a catch crop increased values by 7.4-18.9% when harvested for fodder and by 3.8-6.5% when ploughed in.
  • Authors:
    • Dosdall, L. M.
    • Moyer, J. R.
    • Clayton, G. W.
    • Harker, K. N.
    • Blackshaw, R. E.
    • O'Donovan, J. T.
    • Maurice, D. C.
    • Turkington, T. K.
  • Source: Crop Protection
  • Volume: 26
  • Issue: 3
  • Year: 2007
  • Summary: In western Canada, the move to integrated weed management (IWM) with reduced dependence on herbicides is being driven by low crop prices, weed resistance to herbicides, and environmental concerns. A rational step when implementing IWM is to determine if herbicide application is required in the first place. Crop yield loss models have been developed to assist with this decision. However, the weed economic threshold will be influenced considerably by management practices. Field studies showed that enhancing crop competitiveness through planting competitive varieties at relatively high seeding rates and through strategic fertilizer placement including sub-surface banded or point-injected nitrogen can reduce the impact of weeds on crop yield and the amount of weed seed entering the soil seed bank. Enhancing crop competitiveness also improved herbicide performance, especially when herbicides were applied at reduced doses. The inclusion of an early-cut silage crop in a rotation dramatically reduced wild oat ( Avena fatua L.) populations in barley ( Hordeum vulgare L.) while growing sweet clover ( Melilotus officinalis (L.) Lam) as a green manure in rotation with cereal and oilseed crops showed tremendous potential to suppress weeds. Other studies demonstrated that weed management should not be considered in isolation since it can influence the severity of alternative pests, for example, damage due to Delia spp. in canola ( Brassica napus L.). Further studies are required to examine the cumulative long-term effects of integrating the various weed management practices on all components of the crop ecosystem including weeds, diseases and insects.
  • Authors:
    • Holm, F. A.
    • Sapsford, K. L.
    • Cathcart, J.
    • Hall, L. M.
    • Clayton, G. W.
    • Harker, K. N.
    • O'Donovan, J. T.
    • Hacault, K.
  • Source: Weed Science
  • Volume: 55
  • Issue: 1
  • Year: 2007
  • Summary: There is no published information on the impact of volunteer barley on wheat yield loss or on the economics of controlling barley with a herbicide. With the registration of imazamox-resistant wheat, it is now possible to control volunteer barley in wheat. Thus, the likelihood of growing wheat in rotation with barley may increase. Field experiments were conducted in 2003 and 2004 at Beaverlodge, Lacombe, and Edmonton, AB, Canada, and Saskatoon, SK, Canada, to determine the impact of volunteer barley on yield of imazamox-resistant spring wheat seeded at relatively low (100 kg ha(-1)) and high (175 kg ha(-1)) rates. Barley was seeded at different densities to simulate volunteer barley infestations. Regression analysis indicated that wheat-plant density influenced the effects of volunteer barley interference on wheat yield loss, economic threshold values, and volunteer barley fecundity among locations and years. Econornic thresholds varied from as few volunteer barley plants as 3 m(-2) at Beaverlodge in 2003 and 2004 to 48 m(-2) at Lacombe in 2003. In most cases, wheat yield loss and volunteer barley fecundity were lower and economic thresholds were higher when wheat was seeded at the higher rate. For example, averaged over both years at Beaverlodge initial slope values (percentage of wheat yield loss at low barley density) were 4.5 and 1.7%, and economic threshold values of volunteer barley plants were 3 m(-2) and 8 m(-2) at low and high wheat seeding rates, respectively. Results indicate that volunteer barley can be highly competitive in wheat, but yield losses and wheat seed contamination due to volunteer barley can be alleviated by seeding wheat at a relatively high rate.
  • Authors:
    • Labreuche, J.
    • Thiébeau, P.
    • Mary, B.
    • Laurent, F.
    • Oorts, K.
    • Nicolardot, B.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Soil N mineralization was quantified in two long-term experiments in northern France, in which no-till (NT) and conventional tillage (CT) had been differentiated for 33 years (Site 1) and 12 years (Site 2). Both sites had the same soil type but differed in crop rotation. N mineralization kinetics were assessed in situ in bare soil in both systems for 254 days (Site 1) and 555 days (Site 2) by taking frequent measurements of water and nitrate contents from soil layers and using the LIXIM calculation model. The N mineralization potential was also determined in soil samples incubated under controlled laboratory conditions. Small or non-significant differences in water and nitrate contents between NT and CT were apparent within the soil profiles on both sites. Net mineralization did not differ significantly between sites or tillage treatments. The amount of N mineralized from August 2003 to April 2004 was 6710 kg N ha -1 on Site 1 and 745 kg N ha -1 on Site 2, and 1616 kg N ha -1 from August 2003 to February 2005 on Site 2. The kinetics of N mineralization versus normalized time (equivalent time at constant temperature of 15degreesC and water content at field capacity) were linear during the shorter period (254 days corresponding to 120 normalized days). The slope (N mineralization rate) did not differ significantly between treatments and sites, and the average rate was 0.570.05 kg N ha -1 nd -1. The kinetics were non-linear on Site 2 over the longer period (555 days corresponding to 350 normalized days). They could be fitted to an exponential model with a slope at the origin of 0.62 kg N ha -1 nd -1. The N mineralization kinetics obtained in laboratory incubations for 120-150 normalized days were also almost linear with no significant differences between treatments. Assuming that mineralization took place in the ploughed layer (in CT) or over the same soil mass (in NT) they were in good agreement with the kinetics determined in situ on both sites. The calculated water drainage below the sampled profile was slightly greater in NT due to lower evaporation. The calculated leached N was slightly higher in NT than CT on Site 1, but did not differ between treatments on Site 2. It is concluded that N mineralization and leaching in NT and CT were similar, despite large differences in N distribution within the soil profile and a slight difference in organic N stock.
  • Authors:
    • Labreuche, J.
    • Gréhan, E.
    • Merckx, R.
    • Oorts, K.
    • Nicolardot, B.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1/2
  • Year: 2007
  • Summary: The greenhouse gases CO 2 and N 2O emissions were quantified in a long-term experiment in northern France, in which no-till (NT) and conventional tillage (CT) had been differentiated during 32 years in plots under a maize-wheat rotation. Continuous CO 2 and periodical N 2O soil emission measurements were performed during two periods: under maize cultivation (April 2003-July 2003) and during the fallow period after wheat harvest (August 2003-March 2004). In order to document the dynamics and importance of these emissions, soil organic C and mineral N, residue decomposition, soil potential for CO 2 emission and climatic data were measured. CO 2 emissions were significantly larger in NT on 53% and in CT on 6% of the days. From April to July 2003 and from November 2003 to March 2004, the cumulated CO 2 emissions did not differ significantly between CT and NT. However, the cumulated CO 2 emissions from August to November 2003 were considerably larger for NT than for CT. Over the entire 331 days of measurement, CT and NT emitted 3160269 and 4064138 kg CO 2-C ha -1, respectively. The differences in CO 2 emissions in the two tillage systems resulted from the soil climatic conditions and the amounts and location of crop residues and SOM. A large proportion of the CO 2 emissions in NT over the entire measurement period was probably due to the decomposition of old weathered residues. NT tended to emit more N 2O than CT over the entire measurement period. However differences were statistically significant in only half of the cases due to important variability. N 2O emissions were generally less than 5 g N ha -1 day -1, except for a few dates where emission increased up to 21 g N ha -1 day -1. These N 2O fluxes represented 0.800.15 and 1.320.52 kg N 2O-N ha -1 year -1 for CT and NT, respectively. Depending on the periods, a large part of the N 2O emissions occurred was probably induced by nitrification, since soil conditions were not favorable for denitrification. Finally, for the period of measurement after 32 years of tillage treatments, the NT system emitted more greenhouses gases (CO 2 and N 2O) to the atmosphere on an annual basis than the CT system.
  • Authors:
    • Osborne, S. L.
    • Riedell, W. E.
    • Pikul, J. L. Jr.
  • Source: Recent Research Developments in Soil Science
  • Volume: 2
  • Year: 2007
  • Summary: Maize (Zea mays L.) grown in rotation with high residue crops generally has lower grain yield under no-till than under tilled soil management in the northern US maize belt. Hence, the research objectives were to further characterize soil physical properties, maize grain yield, and seed composition under tilled and no-till soil management following soybean ( Glycine max L.) or winter wheat ( Triticum aestivum L). The two year field study was conducted on a Barnes sandy clay loam soil (fine-loamy, mixed, superactive, frigid Calcic Hapludoll) in eastern South Dakota USA. Research plots were managed under no-till starting in 1996. Tillage treatments (fall chisel plow prior to winter wheat, fall chisel plow plus spring disk-harrow prior to maize and soybean, or no-till) were started in 2001. Tillage and previous crop treatments were arranged in a completely randomized block design with 4 replications. Soil temperatures (30 cm depth) in tilled plots after winter wheat were warmer than no-till plots in June and again in August of the 2004 growing season. In 2003, soil temperatures were very similar across tillage treatments. Soil bulk density (0 to 10 cm depth) and soil penetration resistance (0 to 7 cm depth) were much greater under no-till soil management than under tilled conditions when measured in mid-June (V6 leaf development stage). While tillage treatment affected maize seed oil concentration (4.0% in tilled, 4.3% in no-till), there were no significant previous crop or interaction effects on seed oil or protein concentration. In the warmer and drier year (2003), maize grain yield under tilled conditions was 8.2 Mg ha -1 compared with 8.7 Mg ha -1 under no-till. In the cooler and wetter year (2004), yields were 9.4 Mg ha -1 under tilled soil management and 7.4 Mg ha -1 under no-till. The no-till soil management treatment following winter wheat had 27% lower maize grain yield than the tilled treatments and the no-till following soybeans. We conclude that greater bulk density and penetration resistance levels under no-till soil management, along with cool soil conditions that typically occur in the spring in the northern US maize belt, reduced maize yield under no-till management in soils with moderately low to low internal drainage.