• Authors:
    • Holmes, P.
    • Wiggs, G.
  • Source: Earth Surface Processes and Landforms
  • Volume: 36
  • Issue: 6
  • Year: 2011
  • Summary: The west-central part of South Africa's Free State Province falls within the transition zone between South Africa's sub-humid, temperate grasslands to the east, and the semi-arid Karoo and arid Kalahari to the south and west, respectively. The area is characterized by low rainfall (typically 500 mm or less) with high variability, but environmental conditions allow widespread dryland commercial agriculture (maize, sunflowers and stock farming). However, human activity promotes wind erosion and the area is susceptible to dust emissions. This study is the first to quantify the degree of wind erosion on the agricultural soils in the region under prevailing winter to spring climatic conditions and land management practices. Using arrays of cup anemometers, dust deposition traps and saltation impact sensors (Safires), measurements were made of the key erosivity and erodibility drivers that control the degree of wind erosion. Results demonstrate that significant quantities of dust are mobilized, particularly during the months of September and October. Thresholds of wind erosion are shown to respond particularly closely to changes in surface and aerodynamic roughness ( z0) with the amount of collected dust correlating well with measures of wind erosivity that weight the impact of higher wind speeds. Given the importance of surface roughness in controlling erosion thresholds, results show that the opportunity exists for well designed farming practices to control wind erosion. However, it is likely that climatically driven environmental change will impact on some of the identified controls on erosion (wind power, moisture availability) with the result that the wind erosion hazard is likely to increase within this marginal environment.
  • Authors:
    • Yang, Z.
    • Guan, C.
    • Zhou, H.
    • Fan, G.
    • Xie, W.
  • Source: Nongye Jixie Xuebao = Transactions of the Chinese Society for Agricultural Machinery
  • Volume: 42
  • Issue: 11
  • Year: 2011
  • Summary: Based on the results from 18-year long-term location experiment in dryland experimental area of northern China, the effects of various kinds of straw return to field such as no straw returning (CK), straw mulching (SM), straw crushing (SC), cattle manure (CM) and different fertilization time i. e. spring and autumn on corn yield and water use efficiency were studied. The results showed that the experiment of combining autumn fertilizing with returning stalks to field could increase the yield and water use efficiency of spring maize significantly compared to the spring fertilizing, meanwhile, it decreased the accumulated water consumption and increased the soil water storage amount. The results showed that autumn fertilizing increased 9.71-15.58 t/hm 2 in yield, compared with spring fertilizing. The range of increased in yield was 8.33%-16.19%. The total corn yield and water use efficiency in the past 18-year decreased in the following order: CM > SM > SC > CK. In different rainfall years, the corn yield and water use efficiency were very different. In normal years, the corn yield was highest. In dry years, the water use efficiency of spring maize was highest and yield increasing effect from straw mulching combining with autumn fertilizing was striking.
  • Authors:
    • Wen, Y.
    • Gong, Z.
    • Gu, S.
    • Lu, J.
    • Zhao, J.
  • Source: Transactions of the Chinese Society of Agricultural Engineering
  • Volume: 27
  • Issue: 12
  • Year: 2011
  • Summary: The objective of this study was to distinguish effects of main growing factors on the corn yield under dry-farming conditions. A corn field experiment with three factors and four levels for each factor was conducted using the same corn cultivar and the same design in three consecutive years on a black soil classified as typic udolls of which the available nitrogen is middle but both available phosphorus and potassium are high. The results showed that, the most limiting factors to corn yield were respectively precipitation in growing season (PGS), rate of nitrogen fertilizer and available nitrogen contents of soil. Only when the PGS was greater than 280 mm, was nitrogen fertilizer effect statistically noticeable. The appropriate combination of nitrogen, phosphorus and potassium fertilizers increased the water use efficiency by 24.3% compared to no fertilizer treatment. Corn yield was positively correlated with the available nitrogen contents of soil too, meaning that higher soil available nitrogen contents are favorable to the increase in corn yield.
  • Authors:
    • Jimenez-Munoz, J.
    • Sobrino, J.
    • Julien, Y.
  • Source: International Journal of Applied Earth Observation and Geoinformation
  • Volume: 13
  • Issue: 5
  • Year: 2011
  • Summary: Several previous studies have shown that the inclusion of the LST (Land Surface Temperature) parameter to a NDVI (Normalized Difference Vegetation Index) based classification procedure is beneficial to classification accuracy. In this work, the Yearly Land Cover Dynamics (YLCD) approach, which is based on annual behavior of LST and NDVI, has been used to classify an agricultural area into crop types. To this end, a time series of Landsat-5 images for year 2009 of the Barrax (Spain) area has been processed: georeferenciation, destriping and atmospheric correction have been carried out to estimate NDVI and LST time series for year 2009, from which YLCD parameters were estimated. Then, a maximum likelihood classification was carried out on these parameters based on a training dataset obtained from a crop census. This classification has an accuracy of 87% (kappa=0.85) when crops are subdivided in irrigated and non-irrigated fields, and when cereal crops are aggregated in a single crop, and performs better than a similar classification from Landsat bands only. These results show that a good crop differentiation can be obtained although detailed crop separation may be difficult between similar crops (barley, wheat and oat) due to similar annual NDVI and LST behavior. Therefore, the YLCD approach is suited for vegetation classification at local scale. As regards the assessment of the YLCD approach for classification at regional and global scale, it will be carried out in a further study.
  • Authors:
    • Belgacem, A.
    • Maughan, N.
    • Visser, M.
    • Neffati, M.
  • Source: Journal of Arid Environments
  • Volume: 75
  • Issue: 11
  • Year: 2011
  • Summary: All dryland countries struggle with manmade dryland degradation and climate change will reinforce this trend. In arid Tunisia (100-200 mm annual rainfall), depleted cereal fallows are a prominent feature of the desertified landscape. Based on long-term agro-ecological work with promising native steppe grasses, this work explores the societal barriers to restoring cereal fallows with these species. Interviews were conducted with 23 stakeholders (researchers, local decision makers of development agencies and land users) and 40 statements were drawn from these interviews as well as from written sources. These were sorted by 27 stakeholders (some of whom were interviewed before) following a distinct Q-sorting technique inspired by Q-methodology. Principal Components Analysis of these Q-sorts revealed three major types of barriers. (1) A widespread knowledge barrier was obvious since opinion on several agro-ecological statements was often opposite to the scientific evidence. (2) Strong convictions about the sacred nature of barley cropping and olive growing pointed to a cultural barrier to sowing steppe grasses on cereal fallows; (3) Finally, especially non-scientific agropastoralists expressed a lack of trust in any state-backed project aimed at combating desertification. Without the living proof of economic benefits of reseeding, no spontaneous uptake of reseeding can be expected.
  • Authors:
    • Norris, B.
    • Harkins, H.
    • Burmester, C.
    • Santen, E.
    • Curtis, L.
    • Dougherty, M.
    • Fulton, J.
    • AbdelGadir, A.
  • Source: Crop Management
  • Issue: August
  • Year: 2011
  • Summary: Fluctuations in dryland cotton yield in the Tennessee Valley region of northern Alabama are common and are usually related to irregular drought periods during the growing season. Subsurface drip irrigation (SDI) has gained popularity as a water delivery system for small, irregular-shaped cotton fields. A seven-year study was conducted with the objective to determine the response of seed cotton yield to SDI tape orientation relative to crop row direction and different irrigation rates under dryland conditions of the Tennessee Valley. Seven treatments were tested in a randomized incomplete block design which consisted of three irrigation treatments (33%, 66%, and 99% pan evaporation), two SDI tape orientations (parallel and perpendicular), and a dryland control. All SDI treatments produced yields significantly higher than non-irrigated, dryland cotton in four out of seven years. Maximum yield was obtained at a median pan evaporation water replacement value of 74%. No statistical differences were observed between SDI tape orientations on seed cotton yield in all years except in 1999 when parallel out yielded perpendicular at lower irrigation rates. Results confirm the long-term efficacy of supplemental irrigation to increase seed cotton yield irrespective of SDI tape placement during sporadic periods of drought. These results are applicable only for fields with the same soil type or with similar water movement characteristics.
  • Authors:
    • Batista, C.
    • Lima, T.
    • Neves, J.
    • Oliveira, R.
    • Berger, P.
    • Aquino, L.
  • Source: REVISTA BRASILEIRA DE ENGENHARIA AGRICOLA E AMBIENTAL
  • Volume: 15
  • Issue: 5
  • Year: 2011
  • Summary: The objective was to evaluate the application of phosphorus doses in parcels in the cotton crop in the systems of cultivation under irrigation and rainfed, being aimed the higher efficiency of phosphate fertilization, in comparison to the traditional application, only at sowing. The experiment was carried out in Quartzanic Neossoil, in the North region of Minas Gerais. The adopted design was randomized blocks, with three replicates. The treatments were the doses of 50 and 120 kg ha -1 of P 2O 5 applied in four ways: PS, P1, P2 and P3 [100/0; 75/25; 50/50; 25/75% of the dose of phosphate fertilizer applied, respectively at the sowing and at 35 days after the emergence (DAE)], in the irrigated and rainfed crops. Two additional treatments, without P, in the crop without and with irrigation, completed the eighteen studied treatments. The increase of the P doses increased the dry mass of aerial part and the number of reproductive structures at 80 DAE, the relative efficiency of the phosphate fertilization and the productivity of cotton in bull. The response to P doses occurred only under irrigation. The parceled application of the phosphate fertilizer did not increase the efficiency of the fertilization in the cotton farm in Quartzanic Neossoil.
  • Authors:
    • Asgharzade, A.
    • Tavassoli, A.
    • Esmaeilian, Y.
    • Babaeian, M.
    • Sadeghi, M.
  • Source: Scientific Research and Essays
  • Volume: 6
  • Issue: 17
  • Year: 2011
  • Summary: Barley is a cool-weather cereal grain primarily produced on dryland farms in Sistan region. In order to study the effect of different proportions of manure and chemical fertilizer and water stress on grain yield and grain nutrient content in barley an experiment was conducted as split plot randomized complete block design with three replications in research field of Zabol University, 2009. Water stress treatments consisted of: water stress in grain filling stage (S 1) and control (S 2) as the main factor and different proportions of manure and chemical fertilizer treatment consisted of: 100% manure (N 1), 100% chemical fertilizer (N 2), 50% manure+50% chemical fertilizer (N 3), 75% manure+25% chemical fertilizer (N 4) and control (N 5) as sub factor in this experiment. Results illustrated that the effect of drought stress in grain filling stage treatment on all grain yield and yield components with the exception of ear weight, were significant. Drought stress in grain filling stage strongly decreased grain yield but its effect was not very strong on another traits. With the exception of grain number/ear and ear weight, fertilizer treatments had significant effect on grain yields and yield components. Grain nutrient content not affected by water stress but among different proportions of fertilizer treatments, 100% manure (N 1) caused to increase of these elements in grain.
  • Authors:
    • Trentin, G.
    • Maldaner, I. C.
    • Radons, S. Z.
    • Heldwein, A. B.
    • Grimm, E. L.
    • Bosco, L. C.
  • Source: Revista Brasileira de Engenharia Agrícola e Ambiental
  • Volume: 15
  • Issue: 2
  • Year: 2011
  • Summary: The objective of this study was to determine the effect of different levels of irrigation and chemical control on yield and occurrence of Late Blight in potato cv. Asterix, at Santa Maria - RS. Two experiments were conducted at the Crop Science Department, Federal University of Santa Maria. One experiment was carried out during spring-summer, 2005/2006 and the second, during fall 2006. The experimental design was a complete randomized, with four replications. The Blitecast model was used to indicate the timing of spraying, by accumulating severity values (VS). Sprinkler irrigation was used corresponding to 1.0, 0.75, 0.50 ETm and no irrigation. Results showed that in dry and high temperature periods, yield was affected by irrigation, mainly when crop water demand was supplied with 100% ETm. During wet periods, yield was affected by the efficient control of Late Blight. The Blitecast model with a severity value of 18 (Bli18) was the most efficient for controlling the disease. Irrigations applied at least every three days did not affect Late Blight incidence and development.
  • Authors:
    • Hebbar, K. B.
    • Mayee, C. D.
  • Source: Current Science
  • Volume: 100
  • Issue: 11
  • Year: 2011
  • Summary: There are several reasons why plants wilt. Some of them are over-watering, lack of water, too much sun, not enough sun, too many/much fertilizers, diseases caused by infection, etc. Wilt due to lack of water or other environmental factors generally occurs gradually and hence, the cause of those can be studied and accordingly it can be controlled by devising appropriate management strategies. Moreover, plants recover with appropriate control measures and continue to yield. In this review, we discuss a typical wilt which is sudden and occurs within a few hours. Hence, understanding the cause and devising a control measure are difficult. Its sporadic distribution and untimely occurrence further complicate the effort to find the cause of this wilt. Unlike the wilt mentioned above which occurs due to lack of water, sudden wilt occurs when the soil is suddenly saturated by a downpour of rain and the sun later shines bright and hot. Paradoxically, the physiological responses, i.e. wilt symptoms to those induced by either drought or flooding are similar. However, the causal mechanism is different. Here, we demonstrate that the imbalance in uptake and loss of water under flooding is the cause of sudden/parawilt of cotton. We also discuss how plants with rapid growth rate and climate factors like bright sunshine and high temperature accentuate the problem of parawilt in cotton.