• Authors:
    • Paustian, K.
    • Capalbo, S.
    • Antle, J.
    • Gerow, K.
    • Mooney, S.
  • Source: Climatic Change
  • Volume: 80
  • Issue: 1/2
  • Year: 2007
  • Summary: Several studies have suggested that geostatistical techniques could be employed to reduce overall transactions costs associated with contracting for soil C credits by increasing the efficacy of sampling protocols used to measure C-credits. In this paper, we show how information about the range of spatial autocorrelation can be used in a measurement scheme to reduce the size of the confidence intervals that bound estimates of the mean number of C-credits generated per hectare. A tighter confidence interval around the mean number of C-credits sequestered could increase producer payments for each hectare enrolled in a contract to supply C-credits. An empirical application to dry land cropping systems in three regions of Montana shows that information about the spatial autocorrelation exhibited by soil C could be extremely valuable for reducing transactions costs associated with contracts for C-credits but the benefits are not uniform across all regions or cropping systems. Accounting for spatial autocorrelation greatly reduced the standard errors and narrowed the confidence intervals associated with sample estimates of the mean number of C-credits produced per hectare. For the payment mechanism considered in this paper, tighter confidence intervals around the mean number of C-credits created per hectare enrolled could increase producer payments by more than 100 percent under a C-contract.
  • Authors:
    • Gracia, R.
    • Lopez, M.
    • Arrue, J.
    • Moret, D.
  • Source: European Journal of Agronomy
  • Volume: 26
  • Issue: 1
  • Year: 2007
  • Summary: Winter barley is the major crop on semiarid drylands in central Aragon (NE Spain). In this study we compared, under both continuous cropping (BC) (5-6-month fallow) and a crop-fallow rotation (BF) (16-18-month fallow), the effects of three fallow management treatments (conventional tillage, CT; reduced tillage, RT; no-tillage, NT) on the growth, yield and water use efficiency (WUE) of winter barley during three consecutive growing seasons in the 1999-2002 period. Daily precipitation measurements and monthly measurements of soil water storage to a depth of 0.7 m were used to calculate crop water use (ET) and its components. The average growing season precipitation was 195 mm. Above-ground dry matter (DM) and corresponding WUE were high in years with high effective rainfalls (>10 mm day -1) either in autumn or spring. However, the highest values of WUE for grain yield were mainly produced by effective rainfalls during the time from stem elongation to harvest. Despite the similarity in ET for the three tillage treatments, NT provided the lowest DM production, corresponding to a higher soil water loss by evaporation and lower crop transpiration ( T), indicated by the lowest T/ET ratio values found under this treatment. No clear differences in crop yield were observed among the tillage treatments in the study period. On average, and regardless of the type of tillage, BF provided the highest values of DM and WUE and yielded 49% more grain than BC. These differences between cropping systems increased when water-limiting conditions occurred in the early stages of crop growth, probably due to the additional soil water storage under BF at sowing. Although no significant differences in precipitation use efficiency (PUE) were observed between BC and BF, PUE was higher under the BC system, which yielded 34% more grain than the BF rotation when yields were adjusted to an annual basis including the length of the fallow. The crop yield under BF was not dependent on the increase in soil water storage at the end of the long fallow. In conclusion, this study has shown that, although conventional tillage can be substituted by reduced or no-tillage systems for fallow management in semiarid dryland cereal production areas in central Aragon, the practice of long-fallowing to increase the cereal crop yields is not longer sustainable.
  • Authors:
    • Schumacher, R.
    • Schroeder, K.
    • Li, C.
    • Okubara, P.
    • Lawrence, N.
  • Source: Canadian Journal of Plant Pathology
  • Volume: 29
  • Issue: 3
  • Year: 2007
  • Summary: Soilborne pathogens are important biotic factors in yield reduction in the dryland cereal production region of the Pacific Northwest. Rhizoctonia solani AG-8, Rhizoctonia oryzae, and Pythium spp. are causal agents of root rot, bare patch, and damping-off of wheat ( Triticum aestivum) and barley ( Hordeum vulgare). Although these pathogens can be rapidly and specifically quantified using quantitative real-time PCR, the extraction of Rhizoctonia DNA from agricultural samples is often inconsistent, especially at low pathogen population densities. Using a novel extraction system that uses pressure cycling technology (PCT), we improved the extraction of R. solani AG-8 DNA up to 16-fold and of P. abappressorium DNA up to 2-fold from three types of agricultural soils compared with a bead beating extraction method. PCT also yielded quantifiable amounts of R. solani AG-8 and R. oryzae DNA from lyophilized wheat roots that were otherwise recalcitrant to homogenization. Furthermore, the extractions were so consistent that pathogen quantification generally could be derived from two rather than three or four replicated extracts. Because PCT is performed in a closed system and minimizes sample shearing and heating, it confers a substantial advantage over conventional extraction systems. Here, we report for the first time the application of PCT in a laboratory setting for the improved extraction and quantification of three types of soilborne pathogens in soil samples. The effectiveness of PCT for three soils suggests that it will be beneficial for other hard-to-extract pathogen samples.
  • Authors:
    • Azarnivand, H.
    • Jafari, M.
    • Sharifani, F.
    • Abbasi, H.
    • Sori, M.
  • Source: Iranian Journal of Range and Desert Research
  • Volume: 13
  • Issue: 4
  • Year: 2007
  • Summary: The effects of plant growth on soil quality in the Sagzi plain of Isfahan (Iran) were determined to evaluate the influence of agriculture on the desertification processes in dry lands. Inappropriate crop management significantly affected soil and water salinization which is one of the important processes of desertification. To determine if agriculture is a positive or negative factor for the reclamation of saline soils, improved and degraded factors of desertification in Sagzi plain of Isfahan were considered. Medicago, wheat and barley were evaluated to determine which crop is more effective for soil reclamation. Wheat and barley were selected and compared with derelict land, which was and independent variable in this study. The soils considered were cultivated with these products successively for at least 5 years. Soil samples were then obtained at different depths (0-3, 30-60, 60-90, 90-120, 120-150 cm) and were analysed for CaCO 3, electrical conductivity, organic matter, K +, Mg +, Ca 2+, Na +, CaSO 4, Cl -, sodium adsorption ratio, HCO 3- and SO 4-. Variance analysis showed significant difference between treatments at different depths and that among the three crops, wheat cropping is the best for soil reclamation.
  • 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: Applied Soil Ecology
  • Volume: 36
  • Issue: 2/3
  • Year: 2007
  • Summary: A 2-year field experiment was conducted to evaluate the impact of management practices involving manipulation of quantity and quality of exogenous inputs on soil N-mineralization rate, N availability and microbial biomass in a rice-barley rotation in a tropical dryland agroecosystem. At the beginning of each annual cycle an equivalent amount of N was added through chemical fertilizer and three organic inputs: 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 mixed). The N-mineralization rate was dominated by ammonification in this dryland agroecosystem. N-mineralization exhibited a distinct seasonal pattern, decreasing from the rice period through the summer fallow period, except in Sesbania+wheat straw and wheat straw treatments which showed a slight increase during the early stages of barley period. The rate of N-mineralization showed a significant relationship with soil moisture and microbial biomass N. During the rice period, N-mineralization rate and available-N was highest in the fertilizer treatment followed by Sesbania > Sesbania+wheat straw > wheat straw. During the barley period, highest N-mineralization rate and available-N was observed in Sesbania+wheat straw followed by wheat straw > Sesbania > fertilizer. Adding Sesbania+wheat straw resulted in consistently higher levels of microbial biomass N, N-mineralization rate and available-N through the annual cycle compared to single application of Sesbania and wheat straw, indicating synergy between the two inputs, favoring more efficient utilization of N. It is suggested that mixed application of high and low quality resources can modulate N release, resulting in relatively higher synchronization which can help in minimizing N loss from agroecosystem.
  • 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:
    • Valadyani, A.
    • Ajali, J.
    • Taghavi, D.
    • Fatahi, I.
  • Source: Journal of New Agricultural Science
  • Volume: 3
  • Issue: 7
  • Year: 2007
  • Summary: The main goal of management of agricultural ecosystems is to maximize the energy flow and human's artificial inputs. This investigation was conducted to evaluate the economic efficiency and crop energy of dry farming of barley ( Hordeum vulgare) in Azarbayejan-e-Sharqi province, Iran. Information and data were obtained from barley farmers and Jihad-e-Agriculture organization of the province. In this study, routine scientific methods were used to change input and output data to their equal quantities and then energy efficiency (ratio of produced energy to consumed energy) was calculated. The rate of inputs applied in these fields was 5923.79 kcal/ha and the rate of produced energy was computed 7644.16 kcal/ha. The rate of energy efficiency (the ratio of output/input) was 1.22 for the crop. Results revealed that most used energy in barley cultivation belonged to fertilizers and machinery energy, so consumption of the energy can be reduced and the energy efficiency can be increased for correct management.
  • Authors:
    • Thakare, R.
    • Gupta, V. R.
  • Source: Indian Journal of Agricultural Research
  • Volume: 41
  • Issue: 4
  • Year: 2007
  • Summary: Effect of irrigated and rainfed cropping systems on carbon and nitrogen mineralization was studied. Maximum C and N mineralization observed under irrigated cropping systems than rainfed. Sorghum-chickpea-groundnut showed highest mineralization under irrigated condition. While monocropping and intercropping with legumes enhances the rate of mineralization under rainfed situation. Mineralization was found to be highest during grand growth period of crops. Application of integrated nutrient supply increased C and N mineralization as compared to their individual application. The FYM+wheat straw+green manuring application augmented the mineralization under soybean-wheat crop sequence.
  • Authors:
    • Liebig, M. A.
    • Merrill, S. D.
    • Krupinsky, J. M.
    • Tanaka, D. L.
    • Hanson, J. D.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 4
  • Year: 2007
  • Summary: Producers need to know how to sequence crops to develop sustainable dynamic cropping systems that take advantage of inherent internal resources, such as crop synergism, nutrient cycling, and soil water, and capitalize on external resources, such as weather, markets, and government programs. The objective of our research was to determine influences of previous crop and crop residues (crop sequence) on relative seed and residue yield and precipitation-use efficiency (PUE) for the no-till production of buckwheat ( Fagopyrum esculentum Moench), canola ( Brassica napus L.), chickpea ( Cicer arietinum L.), corn ( Zea mays L.), dry pea ( Pisum sativum L.), grain sorghum ( Sorghum bicolor L.), lentil ( Lens culinaris Medik.), proso millet ( Panicum miliaceum L.), sunflower ( Helianthus annus L.), and spring wheat ( Triticum aestivum L.) grown in the northern Great Plains. Relative seed yield in 2003 for eight of the 10 crops resulted in synergistic effects when the previous crop was dry pea or lentil, compared with each crop grown on its own residue. Buckwheat, corn, and sunflower residues were antagonistic to chickpea relative seed yield. In 2004, highest relative seed yield for eight of the 10 crops occurred when dry pea was the previous crop. Relative residue yield followed a pattern similar to relative seed yield. The PUE overall means fluctuated for seven of the 10 crops both years, but those of dry pea, sunflower, and spring wheat remained somewhat constant, suggesting these crops may have mechanisms for consistent PUE and were not as dependent on growing season precipitation distribution as the other seven crops. Sustainable cropping systems in the northern Great Plains will approach an optimal scheme of crop sequencing by taking advantage of synergisms and avoiding antagonisms that occur among crops and previous crop residues.