• Authors:
    • Grant, C.
    • Cai, D.
    • Wu, X.
    • Sun, Y.
    • Feng, Z.
    • Zhang, D.
    • Zhang, X.
    • Zhao, Q.
    • Meng, C.
    • Dai, K.
    • Yang, Y.
    • Wang, X.
    • Jia, S.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 90
  • Issue: 3
  • Year: 2011
  • Summary: A field micro-plot experiment for winter wheat was conducted in an irrigated winter wheat ( Triticum aestivum)-summer maize ( Zea mays L.) rotation system in Mazhuang, Xinji of Hebei province in the North China Plain, using the 15N isotope method to determine the effects of N application (rates and timing), and irrigation frequency on urea- 15N fate, residual-N and N recovery efficiency (NRE) of wheat. The experiment was conducted under two irrigation treatments (I2 and I3, representing for two and three irrigations, respectively), at three N rates (150, 210, and 270, kg ha -1), divided between two 15N-labeled applications of basal- 15N (90 kg ha -1) and topdress- 15N (60, 120, and 180, kg N ha -1, respectively). The total N uptake by wheat (ranging from 186 to 238 kg ha -1) and the fertilizer-derived N (Ndff, about 34-55%) were measured. The Ndff from labeled basal- 15N and from labeled topdress- 15N were about 15-22% and 16-40%, respectively. The NRE (measured either as recovery in grain or as the total N recovery in the plant) was higher with I3 (39-41 or 47-49%) than with I2 (35-40 or 42-47%), showing maximum NRE in grain of about 40% both at N210 with I2 and at N150 with I3 treatment. The NRE by the first wheat crop (in grain or the total N recovery in plant) was higher with labeled topdress- 15N (39-48 or 45-56%) as compared to that with labeled basal- 15N (30-37 or 36-45%), while the unaccounted N losses were lower with labeled basal- 15N (14-22%) relative to labeled topdress- 15N (14-35%). Higher residual N in soils was found with labeled basal- 15N (41-51%), as compared to labeled topdress- 15N (18-35%). Residual N in the 0- to 150-cm soil depth ranged from 26 to 44% while the unaccounted N losses ranged from 14 to 30%. Recovery of residual N by the 2nd and 3rd crops in the rotation was 5-10% in the maize crop and a further 1.7-3.5% in the subsequent wheat crop. The accumulated N recovery and the unaccounted N losses in continuous wheat-maize-wheat rotations derived from labeled topdress- 15N were 54-64% and 16-37%, respectively while they were 47-53% and 16-28%, respectively from labeled basal- 15N. This study also suggested that an N rate of 210 kg ha -1 (with a ratio of basal-N to topdress-N of 1:1.3) with two irrigation applications could optimize wheat grain yields and NRE, under the water limited conditions in North China Plain.
  • Authors:
    • Castel, J. R.
    • Ballester, C.
    • Jiménez-Bello, M. A.
    • Intrigliolo, D. S.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 10
  • Year: 2011
  • Summary: Leaf temperature is a physiological trait that can be used for monitoring plant water status. Nowadays, by means of thermography, canopy temperature can be remotely determined. In this sense, it is crucial to automatically process the images. In the present work, a methodology for the automatic analysis of frontal images taken on individual trees was developed. The procedure can be used when cameras take at the same time thermal and visible scenes, so it is not necessary to reference the images. In this way, during the processing in batch, no operator participated. The procedure was developed by means of a non supervised classification of the visible image from which the presence of sky and soil could be detected. In case of existence, a mask was performed for the extraction of intermediate pixels to calculate canopy temperature by means of the thermal image. At the same time, sunlit and shady leaves could be detected and isolated. Thus, the procedure allowed to separately determine canopy temperature either of the more exposed part of the canopy or of the shaded portion. The methodology developed was validated using images taken in several regulated deficit irrigation trials in Persimmon and two citrus cultivars (Clementina de Nules and Navel Lane-Late). Overall, results indicated that similar canopy temperatures were calculated either by means of the automatic process or the manual procedure. The procedure developed allows to drastically reduce the time needed for image analysis also considering that no operator participation was required. This tool will facilitate further investigations in course for assessing the feasibility of thermography for detecting plant water status in woody perennial crops with discontinuous canopies. Preliminary results reported indicate that the type of crop evaluated has an important influence in the results obtained from thermographic imagery. Thus, in Persimmon trees there were good correlations between canopy temperature and plant water status while, in Clementina de Nules and Navel Lane-Late citrus cultivars canopy temperature differences among trees could not be related with tree-to-tree variations in plant water status.
  • Authors:
    • Armengot, L.
    • Blanco-Moreno, J. M.
    • Jose-Maria, L.
    • Xavier Sans, F.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 145
  • Issue: 1
  • Year: 2011
  • Summary: Agricultural intensification, at local and landscape scales, has caused a decrease in plant diversity and changes in species composition in cereal fields. To better understand the role of landscape complexity and farming systems in shaping plant assemblages, it is of interest to focus on functional traits rather than on floristic composition, which may help to highlight trends in vegetation patterns. We analysed the relative abundance of various functional attributes (different life forms, growth forms, wind-pollinated species and wind-dispersed species) at three contrasted field positions (boundary, edge and centre) of 29 organic and 29 conventional cereal fields distributed in 15 agrarian localities of NE Spain. Agricultural intensification affected the biological attributes of the vegetation in dryland Mediterranean cereal fields; local factors (farming system and position) had a more prominent role in affecting plant functional composition than the surrounding landscape. Local factors were important for life form distribution, growth form and pollination type, whereas landscape complexity mainly affected the proportion of wind-dispersed species. Therefore, depending on the objective of the study, it is important to select functional attributes sensitive to the different scales of agricultural intensification, especially because landscape complexity and land-use intensity are commonly related.
  • Authors:
    • José-María, L.
    • Sans, F. X.
  • Source: Weed Research
  • Volume: 51
  • Issue: 6
  • Year: 2011
  • Summary: Weed seedbanks are a reserve of weed diversity and can contribute to the prediction of future weed problems in arable fields. Managing seedbanks should therefore help in optimising biodiversity and controlling weed infestations. This study assessed the effects of management system (organic vs. conventional) and landscape complexity on seedbank size and species richness at the edges and centres of Mediterranean dryland cereal fields and examines the relationship between specific management practices and seedbanks. Field edges and organic fields had more species-rich, denser seedbanks than field centres and conventional fields, and landscape complexity had a limited effect on arable seedbanks. Accordingly, the promotion of low-intensity farming practices regardless of landscape complexity, especially at field edges, would be an effective measure for conservation purposes in Mediterranean agroecosystems. Nevertheless, the high seed density of organic seedbanks reveals the need for more effective seedbank management. The analysis of the effects of specific management practices highlights the importance of cleaning crop seeds properly to reduce seedbank size and using complex rotations, especially as this tends to conserve species richness while reducing seed abundance.
  • Authors:
    • Kugbei, S.
  • Source: Journal of Crop Improvement
  • Volume: 25
  • Issue: 3
  • Year: 2011
  • Summary: Production figures in 2008 showed that new private seed enterprises in Afghanistan produced and sold about 12,000 tons of certified wheat seed, which accounted for 95% of the total certified seed produced in the country. At a retail price of about US$1,200 per ton, the enterprises earned an average margin of 20%. When interviewed, the farmers ranked high yield as by far the most important characteristic they sought in improved varieties. Besides yield, the next important attributes were earliness, disease resistance, grain color, and bread making quality. Estimates of on-farm productivity showed that use of improved wheat varieties alone could contribute up to 33% incremental yield under irrigated conditions, whereas the use of quality seed could enhance yield further by 28%. These estimates were obtained under recommended fertilizer rates, in the absence of which yield levels would have declined substantially. Apart from wheat, other major crops the farmers grew varied by regions but in broad terms included rice, vegetables, maize, potato, cotton, barley, watermelon, and alfalfa.
  • Authors:
    • Schubert, A. M.
    • Hudnall, W. H.
    • Booker, J. D.
    • Bronson, K. F.
    • Malapati, A.
  • Source: Journal of Soil and Water Conservation
  • Volume: 66
  • Issue: 5
  • Year: 2011
  • Summary: Sulfate (SO 4) is one of the most important anions in soils and groundwater in semiarid regions, including west Texas. Crops' sulfur (S) requirement is about 10% to 20% of the nitrogen requirements. However, there is far less information on soil test SO 4-S (S in the SO 4 form [sulfate-S]) for the western United States, compared to the humid eastern United States. The deposition of S from the atmosphere has declined nationwide, as coal-fired power plants have been scrubbing their emissions of S. This, combined with greater cotton yields and the lack of S fertilization on the Texas Southern High Plains (SHP) point to the need for a soil profile SO 4-S assessment. The first objective of this study was to assess residual soil profile SO 4-S content in irrigated cotton ( Gossypium hirsutum) fields across a range of soil types and counties of the Texas SHP. The second objective was to compile regional SO 4-S concentration data from the Texas Water Development Board irrigation well water quality database and analyze Ogallala groundwater SO 4-S levels by county, soil map unit, and well depth. Soil profile (0 to 0.9 m [0 to 36 in]) SO 4-S content ranged from 120 to 475 kg ha -1 (107 to 424 lb ac -1) among seven center-pivot fields sampled. About half of this S was in the 0.6 to 0.9 m (24 to 36 in) soil layer, which typically was sandy clay loam or clay loam in texture. Well water SO 4-S concentration ranged from 9 to 220 mg L -1 (ppm) in clayey soils with deep groundwater to sandy soils with shallow groundwater, respectively. Groundwater SO 4-S concentration was greater than the USEPA drinking water standard of 83 mg L -1 in 32% of the wells, especially in the southeastern corner of the study area. There was no consistent relationship between soil map unit and SO 4-S content in the soil profile (0 to 0.9 m). A significant negative relationship between well depth and well water SO 4-S concentration was observed in all the eleven-county study area of the SHP of West Texas. In conclusion, soil profile SO 4 content to 0.9 m is high in SHP irrigated cotton fields and in most cases should be adequate for crop S nutritional requirements.
  • Authors:
    • Chachar, Q. I.
    • Shahzadi, A. K.
    • Mari, J. M.
  • Source: Journal of Agricultural Technology
  • Volume: 7
  • Issue: 1
  • Year: 2011
  • Summary: The study on perception of the problems in farming community in District Hyderabad, Pakistan was conducted through a set of questioners during 2007. Three hundred respondents (growers) were personally interviewed, their responses were tabulated. Data were collected on the basic information about cotton growers such as their ages, education, tenancy statuses, sizes of farm, farming experiences, and living status was asked which would highly influence the use of communication media for the perception of the problems in farming community. The growers of the area stated that irregular supply of irrigation and lack of visit of extension personnel, nonavailability of inputs, and high cost of inputs were common problems of the area. It was also noted that these are the causes for low yield. It is recommended that government should ensure the better facilities for continue supply of irrigation water and pure inputs with minimum rates in the market.
  • Authors:
    • Tahir, M. A.
    • Quddus, M. A.
    • Muhammad, A.
    • Muhammad, A.
    • Nighat, F.
  • Source: Pakistani Journal of Agricultural Science
  • Volume: 48
  • Issue: 1
  • Year: 2011
  • Summary: The paper examined the resource use efficiency of small Bt cotton farmers of Punjab province of Pakistan using the production function approach. Data for the study were obtained from 150 randomly selected Bt cotton farmers from Punjab province using a multistage sampling procedure and then categorized into small, medium and large farmers. Average farm size of small farmer was found to be 5 acres. Regression results indicated that Fertilizer, Spray Number, Irrigation acre inch and labour cost were significantly affecting Bt cotton production while farm size was found non significant. The resource use efficiency analysis showed that efficiency ratios i.e. MVP/MFC for inputs fertilizer (Kg), spray number, irrigation (acre inch) and labour cost (Rs) were found to be 1.5, 3.94, 3.01 and 1.27, respectively. All the efficiency ratios, more than unity indicated the under utilization of all the production inputs under consideration in case of small Bt cotton farmers. Bt cotton production for small Bt farmers had an increasing return to scale with elasticity of production 1.27. Opportunities still exists to increase Bt cotton output in the study area by increasing the level of above mentioned productive resources.
  • Authors:
    • Murari, L.
  • Source: Regional Environmental Change
  • Volume: 11
  • Issue: Supplement 1
  • Year: 2011
  • Summary: One of the targets of the United Nations 'Millennium Development Goals' adopted in 2000 is to cut in half the number of people who are suffering from hunger between 1990 and 2015. However, crop yield growth has slowed down in much of the world because of declining investments in agricultural research, irrigation, and rural infrastructure and increasing water scarcity. New challenges to food security are posed by accelerated climatic change. Considerable uncertainties remain as to when, where and how climate change will affect agricultural production. Even less is known about how climate change might influence other aspects that determine food security, such as accessibility of food for various societal groups and the stability of food supply. This paper presents the likely impacts of thermal and hydrological stresses as a consequence of projected climate change in the future potential agriculture productivity in South Asia based on the crop simulation studies with a view to identify critical climate thresholds for sustained food productivity in the region. The study suggests that, on an aggregate level, there might not be a significant impact of global warming on food production of South Asia in the short term (
  • Authors:
    • Romero, R.
    • Duran, V. H.
    • Jimenez, J. A.
    • Garcia-Tejero, I.
    • Muriel,J . L.
    • Hernandez, A.
  • Source: Acta Horticulturae
  • Issue: 889
  • Year: 2011
  • Summary: Different strategies of deficit irrigation have been studied in an 11-year old citrus trees ( Citrus sinensis L. Osb. 'Navelina') grafted onto Carrizo citrange ( Citrus sinensis L. Osb. * Poncirus trifoliata L. Raf.). A sustained deficit irrigation (SDI) treatment was established, with a water supplied of 60% of the crop evapotranspiration (ET c); and a low-frequency deficit irrigation treatment (LFDI), watered according to the plant-water status. As a control a full irrigated at 100% of ET c was included. Midday stem water potential (Psi stem), stomatal conductance (g s), and micrometric trunk diameter fluctuations were measured during the maximum evapotranspirative demand period to evaluate the plant-water status, and to establish the main relationships between them. The seasonal pattern of the studied variables had a behavior consistent with the applied irrigation volumes. Significant relationships between Psi stem and g s, and the maximum daily shrinkage (MDS) were found. The lowest Psi stem and g s values were registered in the deficit treatments being the MDS significative higher in these treatments than in the control treatment. Yield response was highly influenced by irrigation strategy, being these results for LFDI significant better than SDI. Considering these results and the significant relationships between MDS and Psi stem, LFDI can be a sustainable deficit irrigation strategy, encouraging significant water savings without important impact on yield and fruit quality.