• Authors:
    • Askegaard, M.
    • Olesen, J. E.
    • Kristensen, K.
    • Rasmussen, I. A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 142
  • Issue: 3-4
  • Year: 2011
  • Summary: Two main challenges facing organic arable farming are the supply of nitrogen (N) to the crop and the control of perennial weeds. Nitrate leaching from different organic arable crop rotations was investigated over three consecutive four-year crop rotations in a field experiment at three locations in Denmark (12 years in total). The experimental treatments were: (i) crop rotation, (ii) catch crop and (iii) animal manure. Nitrate leaching was estimated from measured soil nitrate concentration in ceramic suction cells and modelled drainage. There were significant effects on annual N leaching of location (coarse sand > loamy sand > sandy loam) and catch crops (without > with). Including a grass-clover green manure on 25% of the area did not increase N leaching compared with crop rotations without green manure. Also the application of animal manure did not influence N leaching, probably because even in the manured treatments the application rate was lower than crop demand. The results identify management of crop and soil during autumn as the main determinant of N leaching. Nitrate leaching was lowest for a catch crop soil cover during autumn and winter (avg. 20 kg N ha -1), a soil cover of weeds/volunteers had on avg. 30 kg N ha -1, and the largest N leaching losses were found after stubble cultivation (avg. 55 kg N ha -1). The N leaching losses increased with increasing number of autumn soil cultivations.
  • Authors:
    • Dalal, R. C.
    • Allen, D. E.
    • Wang, W. J.
    • Reeves, S.
    • Gibson, I.
  • Source: Soil & Tillage Research
  • Volume: 112
  • Issue: 2
  • Year: 2011
  • Summary: Conservation agricultural practices such as no-till (NT) and crop residue retention (CRR), and nutrient application, increases soil organic C (SOC) and are considered effective measures of C sequestration in soil. However, long-term effects of individual components of conservation agriculture and their interactions on SOC are rarely evaluated; as a result, conflicting findings of these practices on SOC are reported in the literature. We measured SOC and soil total N in a balanced factorial experiment, conducted on a Vertisol, consisting of tillage practices (conventional mechanical tillage, CT; and no-tillage, NT), crop residue management (crop residue burned, CRB; and crop residue retained, CRR) and N fertiliser application (no N, 30 kg N ha -1 year -1; and 90 kg N ha -1 year -1). The site, in a semiarid subtropical region, was cropped with wheat ( Triticum aestivum L.) except for 3 years of barley ( Hordeum vulgare L.), for 40 years using conservation practices. In general, tillage effects on SOC and soil total N were small. Crop residue and N fertiliser interactively increased SOC and total N stocks at 0-0.1 m depth and cumulative stocks at 0-0.2 m and 0-0.3 m depths; that is, CRR increased SOC and soil total N only when N fertiliser was applied, and fertilisation increased SOC and soil total N only under CRR treatment. Depletion of delta 13C values in CRR treatments and delta 15N values in N treatments strongly indicated the contribution of crop residue (and root biomass) and N fertiliser to soil organic matter in this Vertisol. From this study and previous findings from this site, it appears, however, the effects of crop residue retention and N fertiliser occurred in early years, and did not continually increase SOC and total soil N with increasing period of conservation practices.
  • Authors:
    • Allen, D. E.
    • Reeves, S.
    • Menzies, N. W.
    • Dalal, R. C.
    • Wang, W.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 6
  • Year: 2011
  • Summary: Land-use change from perennial grasslands to cultivated croplands leads to reduced soil organic C (SOC) and total N. Among other factors, introduction of annual crops and soil disturbance by tillage may account for reduced amounts of SOC and total N. However, agricultural practices of no-till and N fertilizer application may maintain soil N in cropped soils. We measured soil N changes and N-use efficiency in a field experiment initiated in 1968, consisting of completely randomized tillage practices (conventional mechanical till [CT], and no-till [NT]), crop residue management (residue burned [RB], and residue retained [RR]), and N fertilization (0, 30, and 90 kg N ha -1) on a Vertisol (Ustic Pellusert) over 40 yr. Crops grown were mainly wheat ( Triticum aestivum L.) except for five barley ( Hordeum vulgare L.) crops early in the experiment. Significant effects of treatments on soil total N were primarily confined to the top 0.1-m depth. Soil total N exponentially declined in all treatments even though apparent fertilizer N recoveries during this period (1969-2008) were only 46 and 59% of N applied at 90 and 30 kg N ha -1, respectively. Mineral N in the soil profile (0-1.2 m) ranged from 68 to 496 kg N ha -1. Nitrogen-use efficiency was similar ( P=0.13) under CT and NT in this Vertisol. However, crop residue retention and a low rate of N application had greater N-use efficiency (35-40%) than RB and a high rate of N application (21-25%) under the annual cereal grain cropping system. If perennial grasslands are considered ecological benchmarks for agricultural sustainability, primarily through large root biomass that utilizes water and nutrients efficiently, then the challenge remains to develop cropping systems that successfully mimic grassland ecosystems.
  • Authors:
    • Feng, G.
    • Sharratt, B.
    • Young, F.
  • Source: Journal of Soil and Water Conservation
  • Volume: 66
  • Issue: 4
  • Year: 2011
  • Summary: In the low precipitation zone (<0.3 m [11.8 in] annual precipitation) of the Inland Pacific Northwest, no-tillage continuous spring cereal and no-tillage spring cereal-chemical fallow rotations are being examined as alternatives to the traditional winter wheat-summer fallow rotation for soil conservation. There is limited information, however, regarding the long-term effects of no-tillage cropping systems on soil hydraulic properties in this semiarid region. The objective of this study was therefore to characterize infiltration, water retention, saturated hydraulic conductivity and bulk density of a silt loam that had been subject to various tillage and crop rotations in east-central Washington. Treatments examined included no-tillage spring barley-spring wheat (NTSB-SW), no-tillage spring wheat-chemical fallow (NTSW-ChF), and traditional winter wheat-summer fallow (WW-SF). Soil properties were measured in spring and late summer 2006 due to the vulnerability of the soil to rapidly dry and erode during these seasons. Saturated hydraulic conductivity was determined by the falling-head method, infiltration was measured using a double-ring infiltrometer, and water retention characteristics was assessed by examining the temporal variation of in situ soil water content. NTSB-SW resulted in higher infiltration and saturated hydraulic conductivity, lower bulk density, and larger and/or more continuous pores in the upper soil profile (<0.1 in [<3.9 in] depth) than WW-SF and NTSW-ChE Infiltration and saturated hydraulic conductivity were lower for chemical fallow than for traditional fallow in spring whereas hydraulic conductivity was lower for summer fallow than chemical fallow in late summer. Soil hydrologic properties appeared more favorable for no-tillage continuous spring cereal rotations. These results arc useful for soil and water management and conservation planning in the low precipitation zone of the Inland Pacific Northwest.
  • Authors:
    • Flower, K. C.
    • Crabtree, W. L.
  • Source: Field Crops Research
  • Volume: 121
  • Issue: 1
  • Year: 2011
  • Summary: On acid soils, no-tillage farmers are often advised to apply lime to the soil surface without incorporation by tillage. As such, it can take a number of years before the subsoil acidity is decreased. However, no-tillage seeders vary in the level of soil disturbance caused during seed placement. The consequence of such variations in soil disturbance for the effectiveness of lime in no-tillage cropping has not been explored. Our objectives were (i) to determine if the liming effect could be accelerated by increasing the rate of lime and level of soil disturbance during no-tillage seeding, and (ii) evaluate the effect of no-tillage seeding method, rate of lime and soil pH on yield of wheat, barley, canola and lupins. Three trials, each with a factorial design consisting of four seeding methods and four lime rates, were established in 1999 and continued until 2005. The soil had a texture contrast with about 15-20 cm of sand over yellow sandy clay loam and the initial pH (CaCl 2) at both 0-10 and 10-20 cm was between 4.5 and 4.7. The four seeding treatments were: low disturbance zero-till disc openers (ZT), higher disturbance no-tillage tines with narrow knife-points (NT), higher disturbance full cut seeding with sweeps (FC) for the first three years followed by ZT from then on, and FC for the first year followed by NT thereafter. The four lime rates were 0, 1, 2 and 4 t ha -1. The liming effect was more rapid with the higher disturbance seeding of NT, FCZT and FCNT, compared with ZT; the seeding effect on soil pH diminished with time and was not detected in the subsoil after four years. Higher rates of lime increased this effect and there was no interaction between seeding method and lime rate. This indicated that soil pH under the different seeding methods responded in a similar manner to increased lime. Nonetheless, significant positive linear regressions were found between yield and soil pH for wheat and barley and a negative relationship for lupins. Canola showed no response to soil pH, possibly because establishment was affected by seeding method, and soil pH was not low enough to elicit a response. The ZT seeding method gave lower yields than the other methods for canola and lupins in some years, but had no effect on wheat and barley yields. Higher disturbance at the time of no-till seeding can, therefore, accelerate the liming effect, making earlier economic gains possible.
  • Authors:
    • Lezaún, J. A.
    • Lacasta, C.
    • Ciria, P.
    • Aibar, J.
    • Pardo, G.
    • Zaragoza, C.
  • Source: Chilean Journal of Agricultural Research
  • Volume: 71
  • Issue: 2
  • Year: 2011
  • Summary: Under semiarid conditions the response of cereal crops to chemical fertilizers and weed control practices with herbicides is often reduced. In fact, the economic profitability of agricultural production in many dryland regions is critically affected by high costs of inputs and low crop yields. As a solution, cropping systems like organic farming, obtaining similar yields and promoting environmental sustainability by reducing fertilizer and herbicides, could be an alternative to conventional systems. In this study, 23 trials were performed in five semiarid regions of Spain during 5 yr to compare different fertilizers and weed control methods on durum wheat ( Triticum durum Desf.) and barley ( Hordeum vulgare L.) yields. The following rotation pattern was developed on the experimental plots: fallow-barley-ground ploughed vetch ( Vicia sativa L.)-durum wheat. Plots either received organic fertilizer, chemical fertilizer, or no fertilizer. In addition, three levels of weed control were applied in cereal plots: flex-tine harrow tillage, conventional herbicide, and no weeding. The results indicated that neither the fertilization nor the weed control have effect on the yield crop.
  • Authors:
    • Lenssen, A. W.
    • Sainju, U. M.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 2
  • Year: 2011
  • Summary: Forages grown in rotation with or without cereals to sustain dryland soil water content and crop production may influence N dynamics. We evaluated the effect of alfalfa ( Medicago sativa L.) and durum ( Triticum turgidum L.)-annual forage cropping sequences on above-(stems+leaves) and belowground (roots) biomass N, dryland soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH 4-N, and NO 3-N contents at the 0- to 120-cm depth in northeastern Montana from 2002 to 2005. Cropping sequences were continuous alfalfa (CA), durum-barley ( Hordeum vulgare L.) hay (D-B), durum-foxtail millet ( Setaria italica L.) hay (D-M), durum-Austrian winter pea ( Pisum sativum L.)/barley mixture hay (D-P/B), and durum-fallow (D-F). From 2002 to 2005, total above- and belowground biomass N was 20 to 97 kg N ha -1 greater under CA than other treatments. In 2005, STN, PON, and PNM were 7 to 490 kg N ha -1 greater under CA than D-M, D-B, and D-P/B at 0 to 30 cm but varied by treatment at other depths. In contrast, MBN at 0 to 15 cm and NH 4-N content at 30 to 90 cm were 23 to 37 kg N ha -1 greater under D-B than D-M and D-F. The NO 3-N content at 0 to 120 cm was 65 to 107 kg N ha -1 greater under D-P/B than other treatments. Even though haying removed a greater amount of N, alfalfa increased surface soil N storage and mineralization and reduced the potential for N leaching compared with durum-annual forages, probably due to increased root growth or N 2 fixation. Durum-pea/barley hay, however, increased N mineralization and availability in subsoil layers, probably due to greater root N concentration or downward movement of water-soluble N.