• Authors:
    • Sharaiha, R.
    • Molla, A.
  • Source: Lucrari Stiintifice, Universitatea de Stiinte Agricole Si Medicina Veterinara "Ion Ionescu de la Brad" Iasi, Seria Agronomie
  • Volume: 52
  • Issue: 1
  • Year: 2009
  • Summary: Mixed intercropping of barley and wheat has been reported as the practice of smallholder farmers in some dryland areas of Ethiopia. However, this cropping system has not yet received the attention of research. Therefore, this study was conducted to determine the level of competition and yield advantage in barley and wheat mixed intercropping under different stress levels of moisture deficit. One pot and one field experiments were conducted to address these objectives. In the pot experiment, three irrigation water levels (75-80, 50-55, and 25-30% depletion of soil available water), five intercropping ratios (%) of barley to wheat in a replacement series (100/0, 75/25, 50/50, 25/75, and 0/100), and four planting densities (4, 8, 12 and 16 plants/pot) were studied in a split-split plot design and had three sets so as to harvest at tillering, heading and maturity stages. In the field, the five intercropping ratios and the four water levels supplied by sprinkler irrigation system were studied in a split-plot design. Intra- and inter-specific competition decreased with decreasing stress levels of moisture deficit; but increased with increasing planting densities in all harvesting stages in the pot experiment. However, both competition types were higher at tillering stage but progressively decreased in later harvesting stages. Intraspecific competition was more important for barley at early stages and for wheat at later stages of the growing period. Both pot and field experiments proved that barley was less competitive than wheat towards the reproductive stage. Yield advantage of mixed intercropping of barley and wheat increased with increasing stress levels of moisture deficit under study. Yield advantage and productivity tended to be dominated by the higher yielding crop species in the mixture. This result suggests mixed intercropping of barley and wheat is not a priority in areas where moisture is not limiting in amount and distribution. It is advisable to use 50% barley+50% wheat ratio since it is difficult to predict which crop performs better than the other in such unpredictable rainfall conditions of the drylands.
  • Authors:
    • Zaragoza, C.
    • Aibar, J.
    • Cavero, J.
    • Pardo, G.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 84
  • Issue: 3
  • Year: 2009
  • Summary: Under semiarid conditions the response of crops to synthetic fertilizers is often reduced. Organic fertilizers can be used to provide a continuous source of nutrients for the crops. The soil nitrogen and crop yield in a rotation of durum wheat ( Triticum durum)-fallow-barley ( Hordeum vulgare)-vetch ( Vicia sativa) were studied during 4 years when synthetic fertilizer (chemical), compost (organic) or no fertilizer (control) were applied in a field with high initial contents of soil NO 3-N (>400 kg N ha -1), phosphorus (22 mg kg -1) and potassium (>300 mg kg -1). Changes in soil organic matter, phosphorus and potassium were also measured. During the crop period, chemical fertilization significantly increased the content of soil NO 3-N in the first 0.30 m of soil with respect to organic fertilization and the control. The yield of wheat and barley was not increased after applying chemical or organic fertilizer with respect to the unfertilized plots. The estimated losses of nitrogen were similar for the three types of fertilization, as well as the uptake of nitrogen for the total biomass produced. The initial levels of organic matter and phosphorus were maintained, even in the plots that were not fertilized, while the potassium decreased slightly. Thus, the rotation and burying of crop residues were enough to maintain the crop yield and the initial content of nutrients.
  • Authors:
    • Murari, S.
    • Masri, S.
    • Ryan, J.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 40
  • Issue: 1/6
  • Year: 2009
  • Summary: Recent concerns about the role of carbon (C) in climate change and the implications about soil organic matter (SOM) for sustainable use of soils have underlined the need to examine the role of SOM in cropping systems, particularly in fragile ecosystems. Accordingly, we examined the changes that occur in total SOM and in its more reactive fractions, labile and biomass C, within a long-term, cereal-based crop rotation trial. The rotations were wheat ( Triticum turgidum var durum) grown after vetch ( Vicia sativa), medic ( Medicago sativa), chickpea ( Cicer arietinum), lentil ( Lens culinaris), fallow, a summer crop, melon ( Citrullus vulgaris), and after wheat (i.e., continuous wheat). Secondary treatments involved nitrogen (N) fertilizer application and variable grazing intensity. Uncropped microplots were established in the main rotation plots, and in the fallow and medic ones with variable grazing. Total SOM and labile and microbial biomass C were periodically measured in the rotations throughout the cropping season. Medic and vetch were highest in the three C forms, with fallow always lowest. All forms changed with sampling time throughout the season. Organic matter decreased from 1.48% in February to 1.15% in August after cropping. Although labile C followed a similar pattern, with a large falloff between the May and August sampling, biomass C increased initially, remained stable for a few months, and decreased at the last two samplings. Although all three C forms were highest in the zero-grazing in the fallow and medic rotations, the effect of grazing was not significant. Thus, although organic C can be built up in the soil to varying extents depending on the crop rotation, it is a dynamic entity, especially the labile and biomass fractions, having implications for crop growth and soil quality.
  • Authors:
    • Murari, S.
    • Pala, M.
    • Masri, S.
    • Ryan, J.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 40
  • Issue: 1/6
  • Year: 2009
  • Summary: Mediterranean agriculture is mainly rainfed, with drought being the main crop production constraint, and is based on cereals, wheat ( Triticum spp), and barley ( Hordeum vulgare). Fallow was a traditional practice to conserve soil moisture, but because of land-use pressure it is giving way to cereal monoculture, which is unsustainable. The substudy reported here was part of a long-term rotation trial that sought to examine alternative crop rotation options, that is, durum wheat ( T. durum var durum) in rotation with fallow, summercrop (melon, Citrullus vulgaris), wheat (continuous cropping), chickpea ( Cicer arietinum), lentil ( Lens culinaris), vetch ( Vicia sativa), and medic ( Medicago spp). Ancillary treatments involved nitrogen (N) applied to the cereal phase and variable stubble grazing intensity (stubble retention, medium grazing, and heavy grazing or complete stubble removal). This substudy, conducted in the final 3 years of the 14-year trial, involved sampling soil and plants within the cropped rotation plots and sampling soil within bare microplots in selected larger rotation plots. We measured N forms in soil samples at different depths and throughout the seasons. Despite variation within and between seasons, the rotation effect of enhanced N was significant and consistent, being highest for vetch and medic, intermediate for chickpea and lentil, and least for continuous cereal, summer crop, and fallow. Therefore, legume-based cereal rotations can enhance soil N and thus save on N fertilizer. In bare microplots, total N decreased, labile N was inconsistent, mineral N increased, and biomass N increased and remained stable during the cropping season and then sharply declined. The nutrient dynamic data complemented the crop yield, water-use efficiency, and soil aggregation data from the trial to support the argument for using legumes in cereal rotations in place of fallow and continuous cereal cropping.
  • Authors:
    • Jabro, J.
    • Caesar-TonThat, T.
    • Sainju, U.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 5
  • Year: 2009
  • Summary: Tillage and cropping sequence may influence C and N sequestration, microbial activities, and N mineralization in dryland soil aggregates. We evaluated the 21-yr effect of tillage and cropping sequence combinations on C and N fractions in aggregates of a Dooley sandy loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls) at the 0- to 20-cm depth in eastern Montana. Tillage and cropping sequences were no-tilled continuous spring wheat (NTCW) ( Triticum aestivum L.), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat-barley ( Hordeum vulgare L.) (1984-1999) followed by spring wheat-pea ( Pisum sativum L.)(2000-2004)(FSTW-B/P), and spring-tilled spring wheat-fallow (STW-F). Carbon and N fractions were soil organic C (SOC), total N (STN), particulate organic C and N (POC and PON), microbial biomass C and N (MBC and MBN), potential C and N mineralization (PCM and PNM), NH 4-N, and NO 3-N. Aggregate proportion was greater in NTCW than in FSTCW in the 4.75- to 2.00-mm aggregate-size class at 0 to 5 cm but was greater in STW-F than in STCW in the 2.00- to 0.25-mm size class at 5 to 20 cm. After 21 yr, STW-F reduced SOC, STN, POC, and PON concentrations in aggregates by 34 to 42% at 0- to 5-cm and by 20 to 32% at 5- to 20-cm compared with NTCW and STCW. The PCM and MBC were greater in NTCW and STCW than in STW-F in the
  • Authors:
    • Evans, R.
    • Lenssen, A.
    • Caesar-Tonthat, T.
    • Sainju, U.
    • Kolberg, R.
  • Source: Soil & Tillage Research
  • Volume: 103
  • Issue: 2
  • Year: 2009
  • Summary: Information on N cycling in dryland crops and soils as influenced by long-term tillage and cropping sequence is needed to quantify soil N sequestration, mineralization, and N balance to reduce N fertilization rate and N losses through soil processes. The 21-yr effects of the combinations of tillage and cropping sequences was evaluated on dryland crop grain and biomass (stems+leaves) N, soil surface residue N, soil N fractions, and N balance at the 0-20 cm depth in Dooley sandy loam (fine-loamy, mixed, frigid, Typic Argiboroll) in eastern Montana, USA. Treatments were no-tilled continuous spring wheat ( Triticum aestivum L.) (NTCW), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat-barley ( Hordeum vulgare L.) (1984-1999) followed by spring wheat-pea ( Pisum sativum L.) (2000-2004) (FSTW-B/P), and spring-tilled spring wheat-fallow (STW-F). Nitrogen fractions were soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH 4-N, and NO 3-N. Annualized crop grain and biomass N varied with treatments and years and mean grain and biomass N from 1984 to 2004 were 14.3-21.2 kg N ha -1 greater in NTCW, STCW, FSTCW, and FSTW-B/P than in STW-F. Soil surface residue N was 9.1-15.2 kg N ha -1 greater in other treatments than in STW-F in 2004. The STN at 0-20 cm was 0.39-0.96 Mg N ha -1, PON 0.10-0.30 Mg N ha -1, and PNM 4.6-9.4 kg N ha -1 greater in other treatments than in STW-F. At 0-5 cm, STN, PON, and MBN were greater in STCW than in FSTW-B/P and STW-F. At 5-20 cm, STN and PON were greater in NTCW and STCW than in STW-F, PNM and MBN were greater in STCW than in NTCW and STW-F, and NO 3-N was greater in FSTW-B/P than in NTCW and FSTCW. Estimated N loss through leaching, volatilization, or denitrification at 0-20 cm depth increased with increasing tillage frequency or greater with fallow than with continuous cropping and ranged from 9 kg N ha -1 yr -1 in NTCW to 46 kg N ha -1 yr -1 in STW-F. Long-term no-till or spring till with continuous cropping increased dryland crop grain and biomass N, soil surface residue N, N storage, and potential N mineralization, and reduced N loss compared with the conventional system, such as STW-F, at the surface 20 cm layer. Greater tillage frequency, followed by pea inclusion in the last 5 out of 21 yr in FSTW-B/P, however, increased N availability at the subsurface layer in 2004.
  • Authors:
    • Caesar-TonThat, T.
    • Lenssen, A.
    • Sainju, U.
    • Evans, R.
  • Source: Agronomy Journal
  • Volume: 101
  • Issue: 2
  • Year: 2009
  • Summary: Novel management practices are needed to improve the declining dryland crop yields and soil organic matter contents using conventional farming practices in the northern Great Plains. We evaluated the 21-yr effect of tillage and cropping sequence on dryland grain and biomass (stems+leaves) yields of spring wheat ( Triticum aestivum L.), barley ( Hordeum vulgare L.), and pea ( Pisum sativum L.) and soil organic matter at the 0- to 20-cm depth in eastern Montana, USA. Treatments were no-tilled continuous spring wheat (NTCW), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat-barley (1984-1999) followed by spring wheat-pea (2000-2004) (FSTW-B/P), and the conventional spring-tilled spring wheat-fallow (STW-F). Spring wheat grain and biomass yields increased with crop growing season precipitation (GSP) and were greater in STW-F than in FSTCW and FSTW-B/P when GSP was
  • Authors:
    • Sonu, S.
    • Nandita, G.
    • Singh, K.
  • Source: Applied Soil Ecology
  • Volume: 42
  • Issue: 3
  • Year: 2009
  • Summary: In view of the significance of agricultural soils in affecting global C balance, the impact of manipulation of the quality of exogenous inputs on soil CO 2-C flux was studied in rice-barley annual rotation tropical dryland agroecosystem. Chemical fertilizer, Sesbania shoot (high quality resources), wheat straw (low quality resource) and Sesbania+wheat straw (high+low quality), all carrying equivalent recommended dose of N, were added to soil. A distinct seasonal variation in CO 2-C flux was recorded in all treatments, flux being higher during rice period, and much reduced during barley and summer fallow periods. During rice period the mean CO 2-C flux was greater in wheat straw (161% increase over control) and Sesbania+wheat straw (+129%) treatments; however, during barley and summer fallow periods differences among treatments were small. CO 2-C flux was more influenced by seasonal variations in water-filled pore space compared to soil temperature. In contrast, the role of microbial biomass and live crop roots in regulating soil CO 2-C flux was highly limited. Wheat straw input showed smaller microbial biomass with a tendency of rapid turnover rate resulting in highest cumulative CO 2-C flux. The Sesbania input exhibited larger microbial biomass with slower turnover rate, leading to lower cumulative CO 2-C flux. Addition of Sesbania to wheat straw showed higher cumulative CO 2-C flux yet supported highest microbial biomass with lowest turnover rate indicating stabilization of microbial biomass. Although single application of wheat straw or Sesbania showed comparable net change in soil C (18% and 15% relative to control, respectively) and crop productivity (32% and 38%), yet they differed significantly in soil C balance (374 and -3 g C m -2 y -1 respectively), a response influenced by the recalcitrant and labile nature of the inputs. Combining the two inputs resulted in significant increment in net change in soil C (33% over control) and crop yield (49%) in addition to high C balance (152 g C m -2 y -1). It is suggested that appropriate mixing of high and low quality inputs may contribute to improved crop productivity and soil fertility in terms of soil C sequestration.
  • Authors:
    • Machado, S.
    • Smiley, R.
  • Source: Plant Disease
  • Volume: 93
  • Issue: 3
  • Year: 2009
  • Summary: Wheat ( Triticum aestivum) in low-precipitation regions of eastern Oregon and Washington is grown mostly as rainfed biennial winter wheat (10-month growing season) planted into cultivated fallow (14-month crop-free period). There are increasing trends for cultivated fallow to be replaced by chemical fallow and for spring cereals to be planted annually without tillage. Most fields are infested by the root-lesion nematodes Pratylenchus neglectus or P. thornei. A replicated multiyear experiment was conducted to compare cropping systems on soil infested by P. neglectus. Populations became greater with increasing frequency of the host crops mustard, pea, and wheat. Annual winter wheat had the highest P. neglectus populations, the lowest capacity to extract soil water, and a lower grain yield compared with wheat grown biennially or rotated with other crops. Populations of P. neglectus did not differ for cultivated versus chemical fallow. Lowest populations occurred in annual spring barley. Winter wheat yield was inversely correlated with the population of P. neglectus. Measures to monitor and to reduce the population of P. neglectus in Pacific Northwest wheat fields are recommended.
  • Authors:
    • Singh, K.
    • Nandita, G.
    • Alka, S.
    • Ritu, M.
    • Sonu, S.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 5
  • Year: 2009
  • Summary: The application of organic amendments in agroecosystems has been widely recommended, but the impact of their C/N ratio on the stabilization and sequestration of soil organic carbon (SOC) is often unaccounted for. The influence of the C/N ratio of amendments on soil physicochemical properties in a rice ( Oryza sativa var. NDR97)-barley ( Hordeum vulgare var. Lakhan) rotation tropical dryland agroecosystem was compared with an undisturbed grassland. Chemical fertilizer in the form of urea and three organic inputs ( Sesbania aculeata shoot, low C/N ratio; air-dried straw of wheat ( Triticum aestivum var. Malviya 533), high C/N ratio; and S. aculeata shoot+wheat straw, high and low C/N ratio combined) carrying an equivalent amount of N, were added to plots of the agroecosystem once during each annual cycle. Soil water-holding capacity (WHC), porosity, SOC, total N, and aggregate stability were improved in the wheat straw and S. aculeata shoot+wheat straw treatments, reaching levels comparable with the grassland. Soil WHC, porosity, and SOC influenced the productivity of the grassland and the agroecosystem. The grassland recorded highest SOC (53% higher relative to control) followed by the wheat straw (+47%), S. aculeata shoot+wheat straw (+37%) and soil total N was greatest in the S. aculeata shoot+wheat straw treatment (+37.5%). Aggregate stability and macroaggregate distribution were also higher in the wheat straw and S. aculeata shoot+wheat straw treatments, however, the microaggregate and silt+clay fractions showed a reverse trend. Management practices with a higher residue-C return in the agroecosystem resulted in increased aggregate stability and aggregate-associated SOC, with C storage attaining levels similar to the natural system.