• Authors:
    • Preez, C.
    • Huyssteen, C.
    • Mnkeni, P.
  • Source: South African Journal of Science
  • Volume: 107
  • Issue: 5/6
  • Year: 2011
  • Summary: The decline of soil organic matter as a result of agricultural land use was identified for a review with the ultimate aim of developing a soil protection strategy and policy for South Africa. Such a policy is important because organic matter, especially the humus fraction, influences the characteristics of soil disproportionately to the quantities thereof present. Part 1 of this review dealt with the spatial variability of soil organic matter and the impact of grazing and burning under rangeland stock production. In this second part of the review, the impact of arable crop production on soil organic matter is addressed. A greater number of studies have addressed the degradation of soil organic matter that is associated with arable crop production than the restoration. However, cropping under dryland has been found to result in significant losses of soil organic matter, which is not always the case with cropping under irrigation. Restoration of soil organic matter has been very slow upon the introduction of conservational practices like zero tillage, minimal tillage, or mulch tillage. Reversion of cropland to perennial pasture has also been found to result in discouragingly slow soil organic matter restoration. Although increases or decreases in soil organic matter levels have occurred in the upper 300 mm, in most instances this took place only in the upper 50 mm. The extent of these changes was dependent inter alia on land use, soil form and environmental conditions. Loss of soil organic matter has resulted in lower nitrogen and sulphur reserves, but not necessarily lower phosphorus reserves. Depletion of soil organic matter coincided with changes in the composition of amino sugars, amino acids and lignin. It also resulted in a decline of water stable aggregates which are essential in the prevention of soil erosion. Although much is known about how arable crop production affects changes in soil organic matter, there are still uncertainties about the best management practices to maintain and even restore organic matter in degraded cropland. Coordinated long-term trials on carefully selected ecotopes across the country are therefore recommended to investigate cultivation practices suitable for this purpose.
  • Authors:
    • Benkherbache, N.
    • Rahali, A.
    • Makhlouf, M.
  • Source: Options Mediterraneennes. Serie A, Seminaires Mediterraneens
  • Issue: 96
  • Year: 2011
  • Summary: The objective of the experiment was to study the development of weed in the durum wheat grown under three cropping techniques, conventional, minimum and no till, after two years of implementation, in the semi arid zone of Setif. Weed seed bank has been estimated in the 0-15 and 15-30 cm soil profile as well as surface weed density. Nineteen species were identified, with a predominance of Polygonum aviculare L., Veronica hederifolia L., Chenopodium vulvaria L. and Avena sterilis. Other species, not less important, are annual dicotyledonous largely known in the region, among which Fumaria densiflora, Fumaria officinalis, Sonchus arvensis L., Papaver rhoeas L., Daucus carota L. and Bifora radiens. Monocotyledons dominated under no till with an average plant density of 57.3 plants/m 2 while the dicotyledonous dominated under shallow tillage with an average plant density of 70.5 plants/m 2. Conventional tillage was characterized by equilibrium between both weed families.
  • 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:
    • Raus, L.
    • Jitareanu, G.
    • Ailincai, C.
  • Source: Lucrari Stiintifice, Universitatea de Stiinte Agricole Si Medicina Veterinara "Ion Ionescu de la Brad" Iasi, Seria Agronomie
  • Volume: 54
  • Issue: 2
  • Year: 2011
  • Summary: The experiment was conducted at the Didactic Station of the "Ion Ionescu de la Brad" University of Agricultural Sciences and Veterinary Medicine of Iasi, Ezareni Farm, during farming years 2007-2009. The experimental site is located in the East part of Romania on a chambic chernozem, with a clay-loamy texture, 6.8 pH units, 3.7% humus content and a medium level of fertilization. The soil has high clay content (38-43%) and is difficult to till when soil moisture is close to the wilting point (12.2%). We have investigated three variants of soil tillage system - conventional tillage, minimum tillage and no-till - in the crop rotation made of wheat and raps. This paper presents the results obtained in winter rape growing as concerns the influence of the tillage method on some soil physical characteristics and yield. Research carried out aimed at developing fundamental knowledge through in-depth inquiries of soil quality indicators of Moldavian Plain, regarding integrated management of soil and water. Research carried out also aimed to quantify the influence of agricultural technologies on physic, hydric, thermic, nutrient and biological soil regime, and ecological impact of these changes on ecological, energetically, hydrological, biogeochemical and breathing soil function, in specific areas of Moldavian Plain. Tillage system modify, at least temporarily, some of the physical properties of soil, such as soil bulk density, penetration resistance, soil porosity and soil structural stability. All the tillage operation was significantly different in their effects on soil properties. The results indicate that soil tillage systems must be adjusted to plant requirements for crop rotation and to the pedoclimatic conditions of the area.
  • Authors:
    • Labreuche, J.
    • Richard, G.
    • Roger-Estrade, J.
  • Source: Cahiers Agricultures
  • Volume: 20
  • Issue: 3
  • Year: 2011
  • Summary: In this paper, we present a review of the literature on the effects of no-ploughing on soil structure, porosity and stability. In the second part, we discuss the consequences on soil erosion in a temperate environment. The effect of reduced tillage on soil physical properties has firstly to be evaluated on soil structure. If carbon accumulation on the soil surface improves aggregate stability, no-ploughing also greatly affects soil porosity. Not only does it decrease during the period following adoption of no-ploughing, but it also changes in nature and connectivity due to weathering, roots and biological activity. However, the efficiency of these factors is site-dependent and varies with the duration of no-ploughing and the crop sequence. Under tropical climates, reduced tillage systems have been proposed to prevent soil erosion while in temperate areas the present increase of no-till is motivated firstly by the decrease of production and mechanization costs. However, the efficiency of the numerous no-plough tillage systems on erosion control is not systematic. The soil must be sufficiently covered by crop residues and the infiltration rate has to remain high enough. This note critically assesses the available results on these two aspects of the effect of reduced tillage on soil physics.
  • Authors:
    • Bahrami, H.
    • Roozbeh, M.
    • Sheikhdavoodi, M. J.
    • Almassi, M.
  • Source: African Journal of Agricultural Research
  • Volume: 6
  • Issue: 23
  • Year: 2011
  • Summary: Degradation of agricultural soils and nutrient losses affected by intensive agriculture and tillage is of environmental and agricultural concerns. These concerns lead to emergence and development of conservative technologies such as conservation tillage systems [reduced tillage (RT) and no-till (NT)] and anionic polyacrylamide (PAM). A study was done in order to investigate the interactive effects of three tillage systems and three PAM concentration on sediment loss, runoff nitrate concentration, nitrogen losses from the soil-plant system and nitrogen recovery. The experimental design was a randomized complete block with split-plot arranged in three replications. The anionic polyacrylamide (PAM) were in three levels of zero (P0), 10 (P10) and 20 (P20) mg L -1 as the main plot and different tillage intensities as the subplot including moldboard plowing plus two disk harrow passes (CT1), one stubble cultivator pass (RT) and moldboard plowing plus one power harrow pass (CT2). The RT treatment relative to CT2 led to soil loss reduction by 23.56% during the first irrigation. The P10 and P20 treatments relative to P0, caused sediment concentration reduction by 98.1 and 98.09% and soil loss reduction by 98.7% and 98.8%, respectively. The RT * P20 treatment had a greater impact in reduction runoff nitrate losses than CT1 * P20 and CT2 * P20 treatments. Losses of N in the fertilized plots and recovery of applied N (RAN) was influenced by both tillage system and PAM application.
  • 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:
    • Torabi-Sirchi, M. H.
    • Saffari, M.
  • Source: American-Eurasian Journal of Agricultural & Environmental Science
  • Volume: 10
  • Issue: 2
  • Year: 2011
  • Summary: Allelopathy is a procedure in which secondary metabolites produced by plants, micro-organisms, viruses and fungi, control growth and development of other biological systems. Some plants may beneficially or antagonistically affect other plants through allelochemical compounds which may be released directly or indirectly from live or dead parts and cause allelopathic and phytotoxic effects. In Kerman (located in the South East of Iran) cultivating corn after winter wheat usually causes less growth and yield. This study was conducted to estimate the effects of different concentrations of two native Iranian wheat (Alvand and Falat) straw extracts on germination, radicle growth, coleoptile length, plant height, leaf area (LA), wet weight (WW) and dry weight (DW) of two hybrid corn varieties (single cross 704 and single cross 647). Results show that the straw extracts, have negative and significant effects on both corn varieties' growth and the significant allelopathic effects remained up to 90 days after wheat harvest; but decreased gradually up to 180 days after harvest. Base on the study results, we advise that before corn cultivation, wheat straw and residues should be eliminated from the field to avoid negative allelopathic effects of wheat straw on corn growth. Hence, it is recommended to let no-till fields as fallow for 6 months; to acquire convenient growth and high yield for corn.
  • Authors:
    • Jabro, J. D.
    • Lartey, R. T.
    • Evans, R. G.
    • Allen, B. L.
    • Sainju, U. M.
    • Lenssen, A. W.
    • Caesar-TonThat, T.
  • Source: Plant and Soil
  • Volume: 338
  • Issue: 1-2
  • Year: 2011
  • Summary: Novel management practices are needed to increase dryland soil organic matter and crop yields that have been declining due to long-term conventional tillage with spring wheat ( Triticum aestivum L.)-fallow system in the northern Great Plains, USA. The effects of tillage, crop rotation, and cultural practice were evaluated on dryland crop biomass (stems+leaves) yield, surface residue, and soil organic C (SOC) and total N (STN) at the 0-20 cm depth in a Williams loam (fine-loamy, mixed, superactive, frigid, Typic Argiustolls) from 2004 to 2007 in eastern Montana, USA. Treatments were two tillage practices [no-tillage (NT) and conventional tillage (CT)], four crop rotations [continuous spring wheat (CW), spring wheat-pea ( Pisum sativum L.) (W-P), spring wheat-barley ( Hordeum vulgaris L.) hay-pea (W-B-P), and spring wheat-barley hay-corn ( Zea mays L.)-pea (W-B-C-P)], and two cultural practices [regular (conventional seed rates and plant spacing, conventional planting date, broadcast N fertilization, and reduced stubble height) and ecological (variable seed rates and plant spacing, delayed planting, banded N fertilization, and increased stubble height)]. Crop biomass and N content were 4 to 44% greater in W-B-C-P than in CW in 2004 and 2005 and greater in ecological than in regular cultural practice in CT. Soil surface residue amount and C and N contents were greater in NT than in CT, greater in CW, W-P, and W-B-C-P than in W-B-P, and greater in 2006 and 2007 than in 2004 and 2005. The SOC and STN concentrations at 0-5 cm were 4 to 6% greater in CW than in W-P or W-B-P in NT and CT from 2005 and 2007. In 2007, SOC content at 10-20 cm was greater in W-P and W-B-P than in W-B-C-P in CT but STN was greater in W-B-P and W-B-C-P than in CW in NT. From 2004 to 2007, SOC and STN concentrations varied at 0-5 cm but increased at 5-20 cm. Diversified crop rotation and delayed planting with higher seed rates and banded N fertilization increased the amount of crop biomass returned to the soil and surface residue C and N. Although no-tillage increased surface residue C and N, continuous nonlegume cropping increased soil C and N levels at the surface layer compared with other crop rotations. Continued return of crop residue from 2004 to 2007 may increase soil C and N levels but long-term studies are needed to better evaluate the effect of management practices on soil C and N levels under dryland cropping systems in the northern Great Plains.
  • Authors:
    • Samuel, A.
    • Domuta, C.
    • Sandor, M.
    • Vuscan, A.
    • Brejea, R.
  • Source: Romanian Agricultural Research
  • Issue: 28
  • Year: 2011
  • Summary: Long-term field trials can provide important information about the effects of soil management practices on soil properties but there are relatively few such trials available. The Agricultural Research and Development Station in Oradea (Bihor county) provided opportunity to study the effects of 18 years of cultivation on preluvosoil. The objective of the reported work was to determine at this site the effects of soil management practices on phosphatase activities as an index of soil biology. Phosphatase (phosphomonoesterase) activities were determined for two years, from 2008 to 2009, in the 0-20, 20-40 and 40-60 cm layers of a preluvosoil, from a long term trials with various tillage practices (no-till and conventional tillage), crop rotation (2 and 6 crop rotations) and fertilization [mineral (NP) fertilization and farmyard-manuring] experiment. The determined activities decreased with increasing sampling depth. No-till - in comparison with conventional tillage - resulted in significantly higher soil phosphatase activities in the 0-20 and in significantly lower activities in the deeper layers. The soil under maize or wheat was more enzyme-active in the 6 than in the 2 crop rotation. In the 2 crop rotation, higher phosphatase activities were recorded under wheat than under maize. Farmyard-manuring of maize - in comparison with mineral (NP) fertilization - led to a significant increase in enzyme activities. Maintenance of enzyme activities over tens of years in agricultural soils is partly attributed to traditional management practices including rotations with legumes, additions of animal manures, and minimum tillage.