• Authors:
    • Srinivasan, R.
    • Williams, J. R.
    • Arnold, J. G.
    • Izaurralde, R. C.
    • Zhang, X.
  • Source: Science of the Total Environment
  • Volume: 463-464
  • Year: 2013
  • Summary: Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However, the inadequacies of the existing carbon algorithm in SWAT limit its application in assessing impacts of human activities on CO2 emission, one important source of greenhouse gasses (GHGs) that traps heat in the earth system and results in global warming. In this research, we incorporate a revised version of the CENTURY carbon model into SWAT to describe dynamics of soil organic matter (SOM)-residue and simulate land-atmosphere carbon exchange. We test this new SWAT-C model with daily eddy covariance (EC) observations of net ecosystem exchange (NEE) and evapotranspiration (ET) and annual crop yield at six sites across the U.S. Midwest. Results show that SWAT-C simulates well multi-year average NEE and ET across the spatially distributed sites and capture the majority of temporal variation of thesetwo variables at a daily time scale at each site. Our analyses also reveal that performance of SWAT-C is influenced by multiple factors, such as crop management practices (irrigated vs. rainfed), completeness and accuracy of input data, crop species, and initialization of state variables. Overall, the new SWAT-C demonstrates favorable performance for simulating land-atmosphere carbon exchange across agricultural sites with different soils, climate, and management practices. SWAT-C is expected to serve as a useful tool for including carbon flux into consideration in sustainable watershed management under a changing climate. We also note that extensive assessment of SWAT-C with field observations is required for further improving the model and understanding potential uncertainties of applying it across large regions with complex landscapes.
  • Authors:
    • Ruzibaev, E.
    • Akramkhanov, A.
    • Lamers, J. P. A.
    • McDonald, A.
    • Mirzabaev, A.
    • Ibragimov, N.
    • Kienzler, K. M.
    • Egamberdiev, O.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Rainfed and irrigated agricultural systems have supported livelihoods in the five Central Asian countries (CAC) for millennia, but concerns for sustainability and efficient use of land and water resources are long-standing. During the last 50 years, resource conserving technologies were introduced in large parts of the rainfed areas while the irrigated areas were expanded largely without considering resource conservation. In more recent years, the use of conservation agriculture (CA) practices has been reported for the different agricultural production (AP) zones in CAC, albeit centering on a single AP zone or on single factors such as crop yield, implements or selected soil properties. Moreover, conflicting information exists regarding whether the current practices that are referred to as 'CA' can indeed be defined as such. Overall information on an application of CA-based crop management in Central Asia is incomplete. This discussion paper evaluates experimental evidence on the performance of CA and other resource conserving technologies in the three main AP zones of CAC, provides an overview of farmer adoption of production practices related to CA, and outlines technical and non-technical challenges and opportunities for the future dissemination of CA practices in each zone. Agronomic (e.g. implements, crop yields, duration. and crop residues), institutional (e.g. land tenure) and economic (e.g. short vs. long-term profitability) perspectives are considered. At present, adoption of CA-based agronomic practices in the rainfed production zone is limited to partial crop residue retention on the soil surface or sporadically zero tillage for one crop out of the rotation, and hence the use of single CA components but not the full set of CA practices. In the irrigated AP zones, CA is not commonly practiced and many of the pre-conditions that typically encourage the rapid spread of CA practices appear to be absent or limiting. Further, our analysis suggests that given the diversity of institutional, socio-economic and agro-ecological contexts, a geographically differentiated approach to CA dissemination is required in the CAC. Immediate priorities should include a shift in research paradigms (e.g. towards more participatory approaches with farmers), development of commercially available reduced and no-till seeders suitable for smaller-scale farm enterprises, and advocacy so that decision makers understand how different policies may encourage or discourage innovations that lead towards more sustainable agricultural intensification in the CAC.
  • Authors:
    • Mailapalli, D. R.
    • Horwath, W. R.
    • Wallender, W. W.
    • Burger, M.
  • Source: Journal of Irrigation and Drainage Engineering
  • Volume: 138
  • Issue: 1
  • Year: 2012
  • Summary: Development of best management practices (BMPs) such as conservation tillage and winter cover crop to mitigate runoff and reduce dissolved chemicals in irrigation runoff is an important objective for controlling surface water pollution attributable to agricultural activities. In this study, the effect of standard tillage (ST), ST with winter cover cropping (STCC), and no-till (NT) management practices on infiltration, runoff, and dissolved organic carbon (DOC) export from furrow-irrigated fields of 244-m length was investigated for summer 2007 and 2008 irrigations. The practices were implemented for 2 years. The average surface residue cover was 11, 44, and 32% for ST, STCC, and NT, respectively, for 2007 and 11, 59, and 61%, respectively, in the following year of the study. Two irrigations in each year were considered for the analysis. The runoff samples were collected from each tillage treatment using ISCO autosamplers at regular time intervals. The infiltration and runoff were estimated using a volume balance model (VBM) by considering a 0.2-m irrigation requirement. Converting from ST to STCC increased the infiltration by 14 and 43% and reduced the runoff by 48 and 43% in 2007 and 2008 irrigations, respectively; whereas, converting ST to NT enhanced the infiltration by 4% in both years and decreased the runoff by 19 and 23% in 2007 and 2008 irrigations, respectively. The authors observed only slightly higher DOC concentrations in STCC, but there was a 24% increase for NT in 2007 irrigations, and both compared to with ST ranged from 3.98 to 5.46 mg/L. The DOC concentration was not significantly different among the treatments in 2008 irrigations (3.48 to 4.6 mg/L). Combining the runoff and DOC concentration effects, the DOC export for STCC was decreased by 55% in both years; whereas, it was decreased by 4 and 27% for NT in 2007 and 2008 irrigations, respectively, compared with ST. Although STCC and NT have higher concentrations, the reduction in export in these treatments is attributable to lower runoff. These results suggest that DOC export can be controlled with STCC practice. No-till showed the same trend, although these results must be confirmed after extended implementation of this practice.
  • Authors:
    • Martiniello, P.
  • Source: Agricultural Sciences
  • Volume: 3
  • Issue: 1
  • Year: 2012
  • Summary: Agricultural systems based on crop rotations favour sustainability of cultivation and productivity of the crops. Wheat-forage crops rotations (annual winter binary mixture and perennial alfalfa meadow) combined with irrigation are the agronomical techniques able to better exploit the weather resources in Mediterranean environments. The experiment aimed to study the effect of 18 years of combined effect of irrigation and continuous durum wheat and wheat-forage rotations on productivities of crops and organic matter of topsoil. The experiments were established through 1991-2008 under rainfed and irrigated treatments and emphasized on the effect of irrigation and continuous wheat and wheat-forage crop rotations on water use efficiency and sustainability of organic matter. The effect of irrigation increased 49.1% and 66.9% the dry matter of mixture and meadow, respectively. Continuous wheat rotation reduced seed yield, stability of production, crude protein characteristics of kernel and soil organic matter. The yearly gain in wheat after forage crops was 0.04 t (ha yr) 1 under rainfed and 0.07 t (ha yr) -1 under irrigation treatments. The crude protein and soil organic matter of wheat rotations, compared to those of continuous wheat under rainfed and irrigated was increase in term of point percentage by 0.8 and 0.5 in crude protein and 5.1 and 4.4 in organic matter, respectively. The rotations of mixture and meadow under both irrigated treatments increased the point of percentage of organic matter over continuous wheat (9.3.and 8.5 in mixture and 12.5 and 9.5 meadow under rainfed and irrigation, respectively). Irrigation reduce the impact of weather on crop growing reducing water use efficiency (mean over rotations) for dry matter production (15.5 in meadow and 17.5 in mixture [L water (kg dry matter) -1]) and wheat seed yield. The effect of agronomic advantages achieved by forage crops in topsoil expire its effect after three years of continuous wheat rotation.
  • Authors:
    • Sampathkumar, T.
    • Pandian, B. J.
    • Mahimairaja, S.
  • Source: Agricultural Water Management
  • Volume: 103
  • Year: 2012
  • Summary: Field experiments were conducted during 2007-2009 to study the effect of deficit irrigation practices through drip irrigation system on soil moisture distribution and root growth in cotton-maize cropping sequence. Creation of soil moisture gradient is indispensable to explore the beneficial effects of partial root zone drying (PRD) irrigation and it could be possible only through ADI practice in paired row system of drip layout, that is commonly practiced in India. In the present study, PRD and deficit irrigation (DI) concepts (creation of soil moisture gradient) were implemented through alternate deficit irrigation (ADI) at two levels of irrigation using drip system. Experimental treatments comprised of six irrigation levels (full and deficit) through drip system with surface irrigation for comparison. Maize was sown after cotton under no till condition without disturbing the raised bed and drip layout. Roots confined to the shallow depth and recorded the lowest values for both the crops under conventional drip irrigation at 100% ETc. Among the deficit irrigation treatments, mild deficit irrigation produced longer lateral roots from both the sides of the plant. Contrary to rooting depth, severe water stress affected the lateral root spread and recorded lower values than other drip irrigation treatments. Soil moisture content (SMC) was low nearer to the plant (at 30 cm across the lateral) and far away (at 30 cm along the lateral) from the plant, irrespective of treatments. The reduction in SMC was increased at all locations as applied water level decreased. It is concluded that alternate watering imposed through ADI at 100% ETc produced longer lateral roots with higher values for root dry mass Alternate deficit irrigation (ADI) resulted uneven distribution of soil moisture content. Among the ADI treatments, ADI at 100% had less uneven distribution than ADI at 80% ETc.
  • Authors:
    • Seufert, V.
    • Ramankutty, N.
    • Foley, J. A.
  • Source: Nature
  • Volume: 485
  • Issue: 7397
  • Year: 2012
  • Summary: Numerous reports have emphasized the need for major changes in the global food system: agriculture must meet the twin challenge of feeding a growing population, with rising demand for meat and high-calorie diets, while simultaneously minimizing its global environmental impacts. Organic farming - a system aimed at producing food with minimal harm to ecosystems, animals or humans - is often proposed as a solution. However, critics argue that organic agriculture may have lower yields and would therefore need more land to produce the same amount of food as conventional farms, resulting in more widespread deforestation and biodiversity loss, and thus undermining the environmental benefits of organic practices. Here we use a comprehensive meta-analysis to examine the relative yield performance of organic and conventional farming systems globally. Our analysis of available data shows that, overall, organic yields are typically lower than conventional yields. But these yield differences are highly contextual, depending on system and site characteristics, and range from 5% lower organic yields (rain-fed legumes and perennials on weak-acidic to weak-alkaline soils), 13% lower yields (when best organic practices are used), to 34% lower yields (when the conventional and organic systems are most comparable). Under certain conditions - that is, with good management practices, particular crop types and growing conditions - organic systems can thus nearly match conventional yields, whereas under others it at present cannot. To establish organic agriculture as an important tool in sustainable food production, the factors limiting organic yields need to be more fully understood, alongside assessments of the many social, environmental and economic benefits of organic farming systems.
  • Authors:
    • Qiu, G.
    • Geng, S.
    • Tsuji, W.
    • Moritani, S.
    • Inoue, M.
    • Wang, S.
    • Zhang, Q.
    • Xie, Q.
  • Source: Journal of Food, Agriculture & Environment
  • Volume: 10
  • Issue: 1 part 2
  • Year: 2012
  • Summary: Determination of the threshold of soil water potential (psi) at which point irrigation should be considered in horticultural plants is important for efficient water use, especially in drylands. The purpose of this study was to determine the threshold for scheduling irrigation during the last week of stage 1 of berry development. Pione grapevine ( Vitis vinifera L., cv. V. labrasca) was allowed to experience decreasing psi monitored by tensiometers after an irrigation event. Berry diameters were measured every hour for 5 days using photogrammetry, a new methodology for monitoring berry size. Net photosynthesis and transpiration rates were measured at various intervals by a portable photosynthesis system. The results showed that after irrigation, the psi decreased slowly during the first 2 days, but started decreasing rapidly when it decreased -6.2 kPa at 10 cm soil depth. Berry diameters increased at night and decreased during the day, and were sensitive to soil moisture status. Berry diameter increased rapidly after irrigation till psi became -3 kPa. In the psi range of -3 to -5.4 kPa, the growth rate decreased, and as psi decreased beyond -5.4 kPa, the berry started shrinking and the shrinkage showed a strong linear relationship with decreasing psi. However, photosynthesis and transpiration rates were unaffected until psi became -9.3 kPa or less. Thus, berry diameter was a more sensitive indicator of water stress than photosynthesis and transpiration. The value of -5.4 kPa should be considered as the threshold psi for scheduling irrigation in the last phase of stage 1 of berry development in grapevines.
  • Authors:
    • [Anonymous]
  • Source: Applied Engineering in Agriculture
  • Volume: 28
  • Issue: 3
  • Year: 2012
  • Summary: This special section includes four papers providing information on the: current status of microsprinkler irrigation in the USA; cotton response to crop row offset and orientation to subsurface drip irrigation laterals; integrated decision support, sensor networks, and adaptive control for wireless site-specific sprinkler irrigation; and a review of mechanical move sprinkler irrigation control and automation technologies.
  • Authors:
    • Refaie, K.
    • Abou-Hussein, S.
    • Abdelraouf, R.
    • El-Metwally, I.
  • Source: Australian Journal of Basic and Applied Sciences
  • Volume: 6
  • Issue: 3
  • Year: 2012
  • Summary: Two field experiments were carried out during growing seasons 2010 and 2011; it was executed in Abo-Ghaleb farm, Cairo-Alex. Rood, 60 Km away from Cairo - Egypt, to study the effect of two irrigation systems (surface and subsurface drip irrigation and three water application rates (50, 75 and 100% from actual irrigation requirements) and three types for pulse irrigation (2 times per day, 3 times per day and 4 times per day and time-off between pulses was 30 minutes) with continuous drip irrigation (one time per day)). The following parameters were studied to evaluate the performance of pulse drip irrigation: (1) Clogging ratio of emitters "CRE", (2) Emission uniformity "EU" (3) Application efficiency "AE", (4) Irrigation water use efficiency of potato "IWUE potato" or water productivity. The results indicated that, CRE decreased by increasing the number of irrigation pulses at (100%, 75% and 50% from WRa) under surface and subsurface drip irrigation. This may be due to pulse technique (cycle on-off) created turbulence in the flow channel and this turbulence prevent particles suspended from accumulation in flow channel and outlets of emitters. The values of CRE under pulse surface drip irrigation were lower than values of CRE under pulse subsurface drip irrigation, this may be due to pulse technique makes vacuum in the network and this vacuum with subsurface drip system will pull more particles which around the emitters through inlets of emitters. From the data of EU, it increased by increasing the number of irrigation pulses (100%, 75% and 50% from WRa) under surface and subsurface drip irrigation. This was due to the positive effect of pulse drip irrigation on reducing CRE. (3) AE increased from 89% under continuous drip irrigation to maximum value where it become 94% after applying pulse technique with 4 pulses at 100% from water requirements under surface drip irrigation, recording an increase of 5.3%. (4) IWUE potato or water productivity increased by increasing number of irrigation pulses especially at (100% and 75% from WRa). IWUE potato increased from 1.44 (kg/m 3) under CDI to maximum value, where it become 2.36 (kg/m 3) after applying pulse technique with 4 pulses at 75% from WRa under SSDI, recording an increase 63.9%, this mean that can save 25% of water requirements per season which equal 2085.6 m 3 ha -1 from irrigation water.
  • Authors:
    • Abdou, A.
  • Source: American-Eurasian Journal of Agricultural & Environmental Sciences
  • Volume: 12
  • Issue: 1
  • Year: 2012
  • Summary: The study revealed the negative impact of international prices' fluctuation and increasing trends upon domestic plans to secure needs of price-subsidized bread in Egypt. Uncertainty with respect to international prices' changes call for neutralizing their influence on domestic prices. In this respect, the study suggested a contract agreement between the local authority and producers to deliver specific quotas of wheat and maize at prices determined in advance on bases of production costs and expected profitability of competitive crops, specifically clover, cotton and rice. The risk may still hold with respect to expected prices of competitive crops, rice in particular, as influenced by international price levels. However, such risk may be minimized if firmly activate regulations of irrigation water use, exerting limits upon rice's total acreage.