• Authors:
    • Kheira, A. A. A.
    • Lamm, F. R.
    • Trooien, T. P.
  • Source: Applied Engineering in Agriculture
  • Volume: 26
  • Issue: 5
  • Year: 2010
  • Summary: A 5-year field study (2004-2008) using irrigation water from an unlined surface reservoir was conducted to examine the effect of dripline depth (0.2, 0.3, 0.4, 0.5, or 0.6 m) on subsurface drip-irrigated rotational crop production of sunflower, soybean, and grain sorghum on a deep silt loam soil in western Kansas. Additional years (1999-2003) of data were included in the analysis of long-term dripline flowrates as affected by dripline depth. Crop seed germination and plant establishment with the subsurface drip irrigation system was not examined in this field study. There were no significant differences in crop yields or yield components in any year of the study with the exception of the number of soybean pods/plant in 2007. In that year, the number of pods/plant was significantly greater for the deeper dripline depths, but this improvement was not reflected in significantly greater soybean yield due to compensation from the other yield components. Measured crop water use and calculated water productivity (yield/water use) also were not significantly affected by dripline depth for any crop in any year. Crop water use varied less than 4% and water productivity varied less than 8% with dripline depth from the mean values for a given crop within a given year, but water productivity tended to be greater for the intermediate 0.4 m dripline depth. There was a tendency for the deeper dripline depths to have greater amounts of plant available soil water and this tendency was stronger as the crop season progressed and for deeper portions of the crop root zone. However, there were neither significant differences in plant available soil water in the upper (0 to 0.9 m) and lower root zones (0.9 to 2.4 m) at physiological maturity of the crop in any year, nor in the total 2.4 m soil profile. The lack of significant differences in crop yields, water use, water productivity and plant available soil water at physiological maturity suggests that dripline depths ranging from 0.2 to 0.6 m are acceptable for crop production of these three crops on the silt loam soils of the region. Measurements of plot dripline flowrates during the period 1999 through 2008 indicated a tendency for deeper disciplines to have reduced flowrates and these flowrate reductions were statistically significant in 2001, 2006, 2007, and 2008. Although the reason for these plot flowrate reductions cannot be fully ascertained, it seems likely they were caused by emitter clogging related to an interaction between dripline depth and irrigation water quality for which the rationale was not determined.
  • Authors:
    • Yang, D. W.
    • Lei, H. M.
  • Source: Global Change Biology
  • Volume: 16
  • Issue: 11
  • Year: 2010
  • Summary: In China, croplands account for a relatively large form of vegetation cover. Quantifying carbon dioxide exchange and understanding the environmental controls on carbon fluxes over croplands are critical in understanding regional carbon budgets and ecosystem behaviors. In this study, the net ecosystem exchange (NEE) at a winter wheat/summer maize rotation cropping site, representative of the main cropping system in the North China Plain, was continuously measured using the eddy covariance technique from 2005 to 2009. In order to interpret the abiotic factors regulating NEE, NEE was partitioned into gross primary production (GPP) and ecosystem respiration (R(eco)). Daytime R(eco) was extrapolated from the relationship between nighttime NEE and soil temperature under high turbulent conditions. GPP was then estimated by subtracting daytime NEE from the daytime estimates of R(eco). Results show that the seasonal patterns of the temperature responses of R(eco) and light-response parameters are closely related to the crop phenology. Daily R(eco) was highly dependent on both daily GPP and air temperature. Interannual variability showed that GPP and R(eco) were mainly controlled by temperature. Water availability also exerted a limit on R(eco). The annual NEE was -585 and -533 g C m-2 for two seasons of 2006-2007 and 2007-2008, respectively, and the wheat field absorbed more carbon than the maize field. Thus, we concluded that this cropland was a strong carbon sink. However, when the grain harvest was taken into account, the wheat field was diminished into a weak carbon sink, whereas the maize field was converted into a weak carbon source. The observations showed that severe drought occurring during winter did not reduce wheat yield (or integrated NEE) when sufficient irrigation was carried out during spring.
  • Authors:
    • Mechlia, N. B.
    • Nagaz, K.
    • Masmoudi, M. M.
  • Source: Options Méditerranéennes : Série A. Séminaires Méditerranéens
  • Issue: 95
  • Year: 2010
  • Summary: Climate change scenarios predict negative impacts on agriculture in the southern Mediterranean regions. Preparedness for increasingly frequent droughts requires a good knowledge on how chronic water shortages may affect production and cropping systems. This work investigates recent variations in agricultural production and in cropping practices in Tunisia as induced by a rapidly changing environment. Using production statistics and climatic records over the period 1984-2005, our analysis shows that variation of the agricultural production could be explained by the Standardized Precipitation Index (R 2=0.45), and that resilience to drought could be evaluated in the same manner. Data from surveys was used to identify adjustments adopted by farmers under the pressure of water scarcity in semi arid (Nabeul) and arid (Medenine) environments. Contrasting changes in cropping systems seem to be taking place for both regions. Contrast is also observed between irrigation strategies adopted by farmers. In Nabeul, large citrus growers having access to water from canal tend to over irrigate whenever water is available in order to minimize risks of water delivery failure from public networks. In contrast small farmers using shallow wells in Medenine seek practices such as deficit irrigation and intercropping in order to optimize water use. It is our view that options to face drought under increasing environmental stress should have a dynamic nature integrating adaptive practices used by farmers.
  • Authors:
    • Patel, B. S.
    • Mehta, R. S.
    • Meena, S. S.
  • Source: The Indian Journal of Agricultural Sciences
  • Volume: 80
  • Issue: 11
  • Year: 2010
  • Summary: A field experiment was conducted during 2006-08 at Sardarkrushinagar to find out optimum irrigation level and weed management practices for getting higher yield of fenugreek ( Trigonella foenum-graecum L.). Monocot weed at 40 days after sowing and at maturity as well as dicot and sedges weed population and dry weight of weeds at 40 days after sowing and at maturity and yield of fenugreek were exhibited significantly higher with irrigation at 1.0 irrigation water/cumulative pan evaporation ratio, followed by 0.8 ratio. Besides weedy check, the highest dry weight and population of weeds at 20 days after sowing was recorded by hand weeding at 20 and 40 days after sowing and hand weeding at 20 days after sowing+inter-culturing at 40 days after sowing but at 40 days after sowing the highest weed population and dry weight was recorded with pre-emergence application of pendimethalin 0.75 kg/ha and pendimethalin 0.75 kg/ha+interculturing at 40 days after sowing and at maturity the lowest dicot and sedge population was recorded by pre-emergence application of pendimethalin 0.75 kg/ha+interculturing at 40 days after sowing but lowest monocot weed population and dry weight of weed was recorded with hand weeding at 20 and 40 days after sowing. Besides, weedy check, the highest weed control efficiency at 20 days after sowing was recorded with pendimethalin 0.75 kg/ha+interculturing at 40 days after sowing but at 40 days after sowing and maturity the highest weed control efficiency was observed with hand weeding at 20 and 40 days after sowing.
  • Authors:
    • Bellaloui, N.
    • Smith, J. R.
    • Mengistu, A.
    • Paris, R. L.
    • Wrather, J. A.
  • Source: Crop Science
  • Volume: 50
  • Issue: 5
  • Year: 2010
  • Summary: Phomopsis seed decay (PSD) of soybean ( Glycine max L. Merr) is primarily caused by Phomopsis longicolla. Currently, percent seed infection is used as a method for evaluating resistance to PSD. However, researchers need a common system for classifying soybean genotypes for their reaction to P. longicolla that is consistent across environments. The purpose of this research was: (i) to evaluate the reaction of a select set of soybean accessions to P. longicolla, and (ii) determine the effects of irrigation and two harvest regimes (normal and delayed) on seed infection. We propose a classification system for comparing reactions to P. longicolla among accessions based on a Phomopsis seed infection index (PSII), derived by dividing the percent seed infection of each accession by percent seed infection values of susceptible standards selected within early and late maturity groups. Percent seed infection by P. longicolla infection was greater when accessions were irrigated during the growing season and harvested at normal maturity. Some lines such as MO/PSD-0259 were rated as resistant to P. longicolla (7% seed infection) when not irrigated and harvested at maturity, but were rated as susceptible (39% seed infection) with irrigation and delayed harvest. The resistance ratings to P. longicolla using percent seed infection and PSII varied among accessions. SS93-6012, for example, had similar ratings for both (9% seed infection and 16% PSII). PI 416942 exhibited some resistance to P. longicolla based on percent seed infection (8%), but no resistance based on PSII (32%). Accessions PI 594478, Delmar, SS93-6012, SS93-6181, PI 594603A, and PI 594712 were classified by PSII as moderately resistant under irrigation and with delayed harvest. These results indicate that simple comparisons of percent seed infection among accessions without irrigation, without delayed harvest, and without a standard control of a similar maturity group might result in false conclusions about resistance to P. longicolla.
  • Authors:
    • Meca, A. V.
    • Popescu, N.
  • Source: Annals of the University of Craiova - Agriculture, Montanology, Cadastre Series
  • Volume: 40
  • Issue: 2
  • Year: 2010
  • Summary: Within our country conditions the wheat, rye, barley, oilseed rape and pea-oat fodder are sown in autumn. They may be grown after crops that are harvested during summer or perennial crops or pastures that are included is crop rotation schemes. In the conditions of our country, crops that are harvested during the summer are: pea-oat fodder, pea, early potato, barley and wheat. After harvesting these crops, there must be done, immediately, the summer plowing because the soil is still moist, resulting a good quality plowing. Any delay conducts to diminishing the yields. Usually, the summer plow is made at 18-20 cm depth. Deeper plow are not necessary on most soil types from our country. Twenty cm deeper plow is need only on clayey soil that easily compacts, when the soil is highly infested by weeds, covered by high straw or when in the last year there was made a shallow plow. Summer plow, no matter the depth must be done along with harrow after plow. During the fall, till drilling, the soil has to be harrowed in order to destroy weeds and to maintain soil loosened.
  • Authors:
    • Portz, G.
    • Chagas, J. P.
    • Bagatini, T.
    • Cogo, Neroli P.
    • Portela, J. C.
  • Source: Revista Brasileira de Ciência do Solo
  • Volume: 34
  • Issue: 4
  • Year: 2010
  • Summary: Soil structure plays a prominent role in plant growth and erosion control, and consequently in food production and soil and water conservation. This research was developed with the objective of implementing and accompanying the restoration process of the structure of a degraded soil, by planting crop sequences under no-tillage (autumn-winter and spring-summer, grass and legume, in single and intercropped systems), and later verifying the relations with water and soil losses caused by rainfall erosion, under distinct surface physical conditions (untitled soil, with and without crust; freshly-tilled soil by chiseling and by chiseling followed by disking after one month, and crop residue covering 100, 18, and 0 %). The field study was developed under simulated rainfall, at the Agriculture Experimental Station of the Federal University of Rio Grande do Sul (EEA/UFRGS), in Rio Grande do Sul State, Brazil, from May 2004 to Decembe, 2007. The six erosion tests, in intervals of about a week, were performed from October to December, 2007. The soil used is an Ultisol, with a sandy clay loam texture in the surface layer and 0.115 in m(-1) average slope steepness, and an advanced degree of degradation. The rains were applied with a rotating-boom rainfall simulator, at a constant intensity of 64 mm h(-1), for 1-3 h. For this study, water and soil loss data were adjusted to a rainfall duration of 1.5 h. Properties of soil and plants were measured in the experimental plots and water erosion in the surface runoff The crop sequences and erosion tests influenced the results of the study significantly, with greater differences in the latter than in the former. The erosive process was more influenced by the external or soil surface than the internal or subsurface physical conditions. In general, all crop sequences were effective in restoring the soil structure in the experimental period. The sequence involving teosinte controlled the rainfall erosion process most effectively with regard to soil and water loss and the one involving corn+cowpea and pearl millet with regard to soil loss. The highest soil and water losses in the study were observed from the soil surface with no mobilization and little crop residue cover, regardless of the presence or type of crust, but especially when this latter was slightly cracked prior to rainfall application. The soil surface entirely covered by crop residue, be it untilled or freshly chiseled, controlled runoff effectively and impeded erosion completely. Soil and water losses from the freshly-disked soil surface chiseled a month earlier, although the soil was the most mobilized of all and bare, were practically zero, opposite to what was expected.
  • Authors:
    • Bengtson, L. E.
    • Fagre, D.
    • Pederson, G.
    • Zeyuan, Q.
    • Prato, T.
    • Williams, J. R.
  • Source: Environmental Management
  • Volume: 45
  • Issue: 3
  • Year: 2010
  • Summary: Potential economic impacts of future climate change on crop enterprise net returns and annual net farm income (NFI) are evaluated for small and large representative farms in Flathead Valley in Northwest Montana. Crop enterprise net returns and NFI in an historical climate period (1960-2005) and future climate period (2006-2050) are compared when agricultural production systems (APSs) are adapted to future climate change. Climate conditions in the future climate period are based on the A1B, B1, and A2 CO(2) emission scenarios from the Intergovernmental Panel on Climate Change Fourth Assessment Report. Steps in the evaluation include: (1) specifying crop enterprises and APSs (i.e., combinations of crop enterprises) in consultation with locals producers; (2) simulating crop yields for two soils, crop prices, crop enterprises costs, and NFIs for APSs; (3) determining the dominant APS in the historical and future climate periods in terms of NFI; and (4) determining whether NFI for the dominant APS in the historical climate period is superior to NFI for the dominant APS in the future climate period. Crop yields are simulated using the Environmental/Policy Integrated Climate (EPIC) model and dominance comparisons for NFI are based on the stochastic efficiency with respect to a function (SERF) criterion. Probability distributions that best fit the EPIC-simulated crop yields are used to simulate 100 values for crop yields for the two soils in the historical and future climate periods. Best-fitting probability distributions for historical inflation-adjusted crop prices and specified triangular probability distributions for crop enterprise costs are used to simulate 100 values for crop prices and crop enterprise costs. Averaged over all crop enterprises, farm sizes, and soil types, simulated net return per ha averaged over all crop enterprises decreased 24% and simulated mean NFI for APSs decreased 57% between the historical and future climate periods. Although adapting APSs to future climate change is advantageous (i.e., NFI with adaptation is superior to NFI without adaptation based on SERF), in six of the nine cases in which adaptation is advantageous, NFI with adaptation in the future climate period is inferior to NFI in the historical climate period. Therefore, adaptation of APSs to future climate change in Flathead Valley is insufficient to offset the adverse impacts on NFI of such change.
  • Authors:
    • Asgharipour, M.
    • Rafiei, M.
  • Source: Advances in Environmental Biology
  • Volume: 4
  • Issue: 3
  • Year: 2010
  • Summary: In search for sustainable agricultural methods for medicinal plants, a field experiment was conducted on isabgol-lentil mono and row intercropping, along with irrigation interval regimes (4-, 7- and 14-days irrigation interval) at the agricultural experimental farm of Zabol University during 2009. The experiment design was split-plot randomized complete block design with four replicates. Main plot treatments were giving irrigation at 4-, 7- and 14-days interval, and subplot treatments consisted of (a) sole isabgol; (b) sole lentil; (c) 1:1 isabgol-lentil intercropping system; (d) 1:3 isabgol-lentil intercropping system; and (e) 3:1 isabgol-lentil intercropping system. The results of the experiment confirmed that drought induced by increasing irrigation interval significantly decreased the growth of both crops and total N concentration of isabgol plants. Results also showed that lentil suppressed biological and grain yield of intercropped isabgol, but the reduction in isabgol yield was compensated by lentil grain yield. Isabgol biological and grain yield was significantly different across cropping systems and the yields were as follows: sole isabgol (281), 1:3 isabgol-lentil (93), 1:1 isabgol-lentil (191), and 3:1 isabgol-lentil (230). Lentil biological and grain yields was also significantly different across the treatments and was sole lentil (1096), 1:3 isabgol-lentil (846), 1:1 isabgol-lentil (644), and 3:1 isabgol-lentil (318). Intercropping isabgol and lentil increased the productivity with LER of 1.10, 1.27 and 1.11 for 1:3 isabgol-lentil, 1:1 isabgol-lentil and 3:1 isabgol-lentil, respectively. In intercrops a significant reduction in LAI, CGR, and also significant increase in leaf and tiller numbers per plant, plant height, spike length, spike numbers per plant, grain numbers per spike and 1000-grain weight of isabgol was observed over sole isabgol. These changes were proportional with row number of isabgol in intercropping. Significant interaction effect of cropping system by irrigation regimes on many cases of measured parameters showed intercropping protects plants from drought. Total concentration of N in isabgol were increased by intercropping, however cropping system by irrigation regimes interaction on N concentration was not significant. These findings suggest that intercropping isabgol-lentil at combination of 1:1 with 7-days irrigation interval may be recommended for yield advantage, more efficient utilization of resources and N concentration on hot and dry regions of South-East Iran.
  • Authors:
    • Razafimpamoa, L. H.
    • Randrianaivoarivony, J. M.
    • Rahetlah, V. B.
    • Ramalanjaona, V. L.
  • Source: African Journal of Food, Agriculture, Nutrition and Development
  • Volume: 10
  • Issue: 10
  • Year: 2010
  • Summary: Forage availability and quality during the dry and cool season is a major constraint to dairy development in the Highlands of Madagascar. The objective of the present study was to determine optimal seeding of oat and common vetch mixtures for increased production and quality of forage. The study was conducted under irrigated conditions in two agro-ecological zones of the Vakinankaratra region in the Highlands of Madagascar. Seed proportions studied were oat-vetch 100:0; 0:100; 50:50 and 50:75. Pure stands of oat and vetch were seeded at the rate of 100 and 60 kg ha -1, respectively. Standard fertilization for forage oat production was uniformly applied on each plot. Pure stands and mixtures were given two successive cuts at flag leaf stage of oat. For both sites and their average, dry matter (DM), feed unit for lactation (UFL), crude protein (CP), and protein digested in the small intestine (PDI) yields were not significantly (p>0.05) different among mixtures and pure stands. The highest yields were obtained from the 50:50 mixture at the first site and from the 50:75 mixture at the second site. According to the two sites' results' average, the highest DM (7.71 t ha -1), UFL (6.08*103 units ha -1), CP (1.64 t ha -1) and PDI (597.1 kg ha -1) yields were obtained from 50:50 mixture. There were no significant differences (p>0.05) in forage quality characteristics except for CP and protein digested in the small intestine when rumen-fermentable nitrogen is limiting (PDIN). Mean CP concentration varied from 15.20% for pure stand of oat to 27.01% for pure stand of vetch. The highest value (178.8 g/kg DM) and the lowest value (103.5 g/kg DM) in PDIN content were obtained from pure stand of oat and pure stand of vetch, respectively. Mixtures had 4.6 to 6.3% more CP content and 15.6 to 39.1% more PDIN content than pure stand of oat. Combined land equivalent ratio values exceeded unity in both mixtures which showed an advantage of intercropping over sole system in terms of the use of environmental resources. As intercropping of oat with vetch at 50:50 (50:30 kg ha -1) mixture achieved maximum yield advantage and forage quality, it could be used as alternative practice of oat sole cropping for high forage and protein production in the Vakinankaratra region.