• Authors:
    • Suyker, A. E.
    • Verma, S. B.
    • Gitelson, A. A.
    • Wardlow, B. D.
    • Sakamoto, T.
    • Arkebauer, T. J.
  • Source: Remote Sensing of Environment
  • Volume: 114
  • Issue: 10
  • Year: 2010
  • Summary: The crop developmental stage represents essential information for irrigation scheduling/fertilizer management, understanding seasonal ecosystem carbon dioxide (CO 2) exchange, and evaluating crop productivity. In this study, we devised an approach called the Two-Step Filtering (TSF) for detecting the phenological stages of maize and soybean from time-series Wide Dynamic Range Vegetation Index (WDRVI) data derived from Moderate Resolution Imaging Spectroradiometer (MODIS) 250-m observations. The TSF method consists of a Two-Step Filtering scheme that includes: (i) smoothing the temporal WDRVI data with a wavelet-based filter and (ii) deriving the optimum scaling parameters from shape-model fitting procedure. The date of key crop development stages are then estimated by using the optimum scaling parameters and an initial value of the specific phenological date on the shape model, which are preliminary defined in reference to ground-based crop growth stage observations. The shape model is a crop-specific WDRVI curve with typical seasonal features, which were defined by averaging smoothed, multi-year WDRVI profiles from MODIS 250-m data collected over irrigated maize and soybean study sites. In this study, the TSF method was applied to MODIS-derived WDRVI data over a 6-year period (2003 to 2008) for two irrigated sites and one rainfed site planted to either maize or soybean as part of the Carbon Sequestration Program (CSP) at the University of Nebraska-Lincoln. A comparison of satellite-based retrievals with ground-based crop growth stage observations collected by the CSP over the six growing seasons for these three sites showed that the TSF method can accurately estimate the date of four key phenological stages of maize (V2.5: early vegetative stage, R1: silking stage, R5: dent stage and R6: maturity) and soybean (V1: early vegetative stage, R5: beginning seed, R6: full seed and R7: beginning maturity). The root mean square error (RMSE) of phenological-stage estimation for maize ranged from 2.9 [R1] to 7.0 [R5] days and from 3.2 [R6] to 6.9 [R7] days for soybean, respectively. In addition, the TSF method was also applied for two years (2001 and 2002) over eastern Nebraska to test its ability to characterize the spatio-temporal patterns of these key phenological stages over a larger geographic area. The MODIS-derived crop phenological stage dates agreed well with the statistical crop progress data reported by the United State Department of Agriculture (USDA) National Agricultural Statistics Service (NASS) for eastern Nebraska's three crop agricultural statistic districts (ASDs). At the ASD-level, the RMSE of phenological-stage estimation ranged from 1.6 [R1] to 5.6 [R5] days for maize and from 2.5 [R7] to 5.3 [R5] days for soybean.
  • Authors:
    • Fontaneli, R. S.
    • Santos, H. P. dos
    • Spera, S. T.
    • Tomm, G. O.
  • Source: Acta Scientiarum. Agronomy
  • Volume: 32
  • Issue: 1
  • Year: 2010
  • Summary: Soil physical characteristics were evaluated, after eight years (1995 to 2003), on a typic Hapludox located in Coxilha, Rio Grande do Sul State, Brazil. Six crop production systems were evaluated: system I (wheat-soybean/black oat+common vetch pasture-corn); system II (wheat-soybean/black oat+common vetch+annual ryegrass pasture-corn); system III (wheat-soybean/black oat+common vetch pasture-pearl millet pasture); system IV (wheat-soybean/black oat+common vetch+annual ryegrass pasture-pearl millet pasture); system V (wheat-soybean, white oat-soybean/black oat+common vetch pasture-pearl millet pasture); and system VI (wheat-soybean/white oat-soybean/black oat+common vetch+annual ryegrass pasture-pearl millet pasture). Soil bulk density and resistance to penetration increased from deeper layer (10-15 cm) to top layer (0-5 cm). In the systems I, V and VI, total porosity decreased and soil bulk density resistance to penetration increased from the deeper layers to top layer surface, due to higher intensity of livestock activities. After eight years of use, the production systems under no-till, involving annual winter and summer pastures and crops, did not promoted soil degradation, in constraining levels, on soil physical attributes.
  • Authors:
    • Suyker, A. E.
    • Verma, S. B.
  • Source: Agricultural and Forest Meteorology
  • Volume: 150
  • Issue: 4
  • Year: 2010
  • Summary: Continuous measurements of CO 2 and water vapor exchanges made in three cropping systems (irrigated continuous maize, irrigated maize-soybean rotation, and rainfed maize-soybean rotation) in eastern Nebraska, USA during 6 years are discussed. Close coupling between seasonal distributions of gross primary production (GPP) and evapotranspiration (ET) were observed in each growing season. Mean growing season totals of GPP in irrigated maize and soybean were 1738114 and 99669 g C m -2, respectively (standard deviation). Corresponding mean values of growing season ET totals were 54527 and 45423 mm, respectively. Irrigation affected GPP and ET similarly, both growing season totals were about 10% higher than those of corresponding rainfed crops. Maize, under both irrigated and rainfed conditions, fixed 74% more carbon than soybean while using only 12-20% more water. The green leaf area index (LAI) explained substantial portions (91% for maize and 90% for soybean) of the variability in GPP PAR (GPP over a narrow range of incident photosynthetically active radiation) and in ET/ET o (71% for maize and 75% for soybean, ET o is the reference evapotranspiration). Water productivity (WP or water use efficiency) is defined here as the ratio of cumulative GPP or above-ground biomass and ET (photosynthetic water productivity=SigmaGPP/SigmaET and biomass water productivity=above-ground biomass/SigmaET). When normalized by ET o, the photosynthetic water productivity (WP ETo) was 18.41.5 g C m -2 for maize and 12.01.0 g C m -2 for soybean. When normalized by ET o, the biomass water productivity (WP ETo) was 27.52.3 g DM m -2 for maize and 14.13.1 g DM m -2 for soybean. Comparisons of these results, among different years of measurement and management practices (continuous vs rotation cropping, irrigated vs rainfed) in this study and those from other locations, indicated the conservative nature of normalized water productivity, as also pointed out by previous investigators.
  • Authors:
    • Thierfelder, C.
    • Wall, P. C.
  • Source: Experimental Agriculture
  • Volume: 46
  • Issue: 3
  • Year: 2010
  • Summary: Conservation agriculture (CA) systems are based on minimal soil disturbance, crop residue retention and crop rotation. Although the capacity of rotations to break pest and disease cycles is generally recognized, other benefits of crop rotations in CA systems are seldom acknowledged and little understood. We monitored different conventional and CA cropping systems over the period from 2005 to 2009 in a multi-seasonal trial in Monze, southern Zambia. Both monocropped maize and different maize rotations including cotton and the green manure cover crop sunnhemp (Crotalaria juncea) were compared under CA conditions, with the aim of elucidating the effects of crop rotations on soil quality soil moisture relations and maize productivity. Infiltration, a sensitive indicator of soil quality, was significantly lower on conventionally ploughed plots in all cropping seasons compared to CA plots. Higher water infiltration rate led to greater soil moisture content in CA maize treatments seeded alter cotton. Earthworm populations, total carbon and aggregate stability were also significantly higher on CA plots. improvements in soil quality resulted in higher rainfall use efficiency and higher maize grain yield on CA plots especially those in a two- or three-year rotation. lit the 2007/08 and 2008/2009 season, highest yields were obtained from direct-seeded maize after sunnhemp, which yielded 74% and 136% more than maize in the conventionally ploughed control treatment with a continuous maize crop. Even in a two-year rotation (maize-cotton), without a legume green manure cover crop, 47% and 38% higher maize yields were recorded compared to maize in the conventionally ploughed control in the two years, respectively This suggests that there are positive effects from crop rotations even in the absence of disease and pest problems. The overall profitability of each system will, however, depend on markets and prices, which will guide the farmer's decision on which, Wally, rotation to choose,
  • Authors:
    • van Rensburg, L. D.
  • Source: South African Journal of Plant and Soil
  • Volume: 27
  • Issue: 1
  • Year: 2010
  • Summary: This is the third soil physics review to be published in South African Journal of Plant and Soil. In the previous reviews the focus was broad and covered almost every aspect of the subject, providing a comprehensive list of contributions in soil physics. For the 25th year anniversary celebration of South African Journal of Plant and Soil, I have chosen to narrow the scope and focus on advances in soil physics in relation to irrigation and dryland agriculture. From a bio-physical viewpoint, South African researchers have made a major contribution to the body of scientific knowledge about irrigation and its application, expressed mainly in the form of irrigation or crop models such as PUTU, SWB and BEWAB. Attention was also given to modern ways of irrigation scheduling based on continuous soil water monitoring. Several irrigation scheduling service providers have adapted their businesses accordingly, with the result that South Africa is probably the leading country in Africa with respect to soil water monitoring and associated communication technology. In contrast, the review has shown that at farm and irrigation scheme level, salt management requires urgent attention. This is necessary as a precautionary measure to protect our natural resources. In the second part of the review the contribution of soil physics in relation to tillage practices is explored, and in particular how these have modified the field water balance components in order to enhance yield and rain water productivity. Based on the results of field experiments, new relationships were established, viz, rainfall and maize yield; water storage and yield; runoff and surface coverage by crop residue mulches; tillage depth, texture and yield relationships. Lastly, the review also showed how the water balance on clay and duplex soils in semi-arid zones can be modified through in-field rainwater harvesting to increase their rain water productivity. This technology has enhanced the livelihoods of many communal families who have applied the technique in their homesteads.
  • Authors:
    • Paula Junior, T. J. de
    • Vieira, R. F.
    • Teixeira, H.
  • Source: Informe Agropecuario Pages:
  • Volume: 31
  • Issue: 254
  • Year: 2010
  • Summary: Despite the growth of bean production, those from small farms still accounts for significant percentage of the total production. Most produced are from Minas Gerais. Maximizing efficiency and minimizing production costs are important factors to increase the profits of small producers. The use of technology and exploitation of natural resources should guide the actions of farmers. Planting dates, cultivars, row spacing and plant density, cropping systems, maize-bean intercropping, irrigation, weed control, pests and diseases as well as practical information technologies from research that aimed at increasing the income of the farmer with the cultivation of beans should be addressed.
  • Authors:
    • Stephenson, D.
    • Miller, D.
    • Williams, B.
  • Source: Louisiana Agriculture
  • Volume: 53
  • Issue: 3
  • Year: 2010
  • Authors:
    • Kolka, R.
    • Asbjornsen, H.
    • Helmers, M. J.
    • Zhou, X. B.
    • Tomer, M. D.
  • Source: Journal of Environmental Quality
  • Volume: 39
  • Issue: 6
  • Year: 2010
  • Summary: Many croplands planted to perennial grasses under the Conservation Reserve Program are being returned to crop production, and with potential consequences for water quality. The objective of this study was to quantify the impact of grassland-to-cropland conversion on nitrate-nitrogen (NO(3)-N) concentrations in soil and shallow groundwater and to assess the potential for perennial filter strips (PFS) to mitigate increases in NO(3)-N levels. The study, conducted at the Neal Smith National Wildlife Refuge (NSNWR) in central Iowa, consisted of a balanced incomplete block design with 12 watersheds and four watershed-scale treatments having different proportions and topographic positions of PFS planted in native prairie grasses: 100% rowcrop, 10% PFS (toeslope position), 10% PFS (distributed on toe and as contour strips), and 20% PFS (distributed on toe and as contour strips). All treatments were established in fall 2006 on watersheds that were under bromegrass (Bromus L.) cover for at least 10 yr. Nonperennial areas were maintained under a no-till 2-yr corn (Zea mays L.)- soybean [Glycine max. (L.) Merr.] rotation since spring 2007. Suction lysimeter and shallow groundwater wells located at upslope and toeslope positions were sampled monthly during the growing season to determine NO(3)-N concentration from 2005 to 2008. The results indicated significant increases in NO(3)-N concentration in soil and groundwater following grassland-to-cropland conversion. Nitrate-nitrogen levels in the vadose zone and groundwater under PFS were lower compared with 100% cropland, with the most significant differences occurring at the toeslope position. During the years following conversion, PFS mitigated increases in subsurface nitrate, but long-term monitoring is needed to observe and understand the full response to land-use conversion.
  • Authors:
    • Shi, C. L.
    • Jin, Z. Q.
    • Zhu, D. W.
  • Source: Jiangsu Journal of Agricultural Sciences
  • Volume: 26
  • Issue: 6
  • Year: 2010
  • Summary: In order to explore the effects of climate change on the crop production and agricultural vegetation on the carbon sequestration ability in the Northeast China in the future, the CERES models ran under both baseline weather and climate change scenarios, which were based on 3 global climate models (GCMs) of GISS, GFDL and UKMO, were used to evaluate the effects of climate change on productivities, moisture status and carbon sequestration of soybean, maize, spring wheat and rice in the Northeast China. In 2040, the growth duration of maize and rice would be shortened by 27 d and 29 d, respectively, while 13 d and 9 d were shortened by for soybean and spring wheat, respectively. The simulated soybean biomass under rainfed scenario was averagely 50% higher than that under the baseline weather, while 10% and 6% increments were simulated for irrigated rice and rainfed maize, respectively. The simulated biomass of rainfed spring wheat would be vulnerable to the climate change. The carbon sequestration ability of crops in the Northeast China would be enhanced from 3.82 t/hm 2 to 4.39 t/hm 2 by the climate change. The results indicated that the climate in the Northeast China would display a warm-dry tendency, and the warming climate would shorten the growth period of crops. The soybean productivities would increase significantly in scenarios of doubled CO 2, and rice and maize productivities would increase slightly, while spring wheat productivities would be unstable due to its sensibility to the moisture. Currently, compared with other regions, the crop carbon sequestration ability in the Northeast China was relative weak, while the climate change in the future would be beneficial for the improvement of crop productivities and the strengthening of agricultural carbon pool.
  • Authors:
    • Constantin, N.
    • Zaharia, G. V.
    • Cociu, A. I.
  • Source: Romanian Agricultural Research
  • Issue: 27
  • Year: 2010
  • Summary: The increase of water use efficiency is very important, especially in water-limited conditions. The research project, carried out on cambic chernozem soil at Fundulea, in 2008 and 2009, had as the main objective the evaluation of contribution of the deep sub-soiling, done before the implementation of this experiment, and of certain tillage systems on over-winter soil water storage, water use efficiency (WUE) and water use as well as on the yield of winter wheat ( Triticum aestivum L.), maize ( Zea mays L.) and soybean [ Glycine max. (L) Merr.], in rotation. The following tillage systems were studied: (1) traditional, with moldboard plough (TS); (2) cizel plough tillage (CS); (3) disc/sweep tillage (DS); (4) strip till, only for row crops (ST); and no till (NT). The over-winter soil water storage estimation was based on calculation of the coefficient of rainfall accumulation during winter (CA), and of capacity of soil water conservation (CC). In the case of maize after wheat, CA was 0.6 on plots with deep sub-soiling, 0.6 on plots without deep sub-soiling, 0.6 with TS, 0.6 with CS, 0.7 with DS, 0.7 with ST, and 0.7 with NT. CC was 85% on plots with deep sub-soiling, 85% on plots without deep subsoiling, 82% with TS, 0.84% with CS, 86% with DS, 86% with ST, and 86% with NT. For soybean after maize, CA was 0.5 on plots with deep sub-soiling, 0.6 on plots without deep sub-soiling, 0.5 with TS, 0.5 with CS, 0.5 with DS, 0.6 with ST, and 0.6 with NT. CC was 77% on plots with deep sub-soiling, 79% on plots without deep sub-soiling, 72% with TS, 78% with CS, 78% with DS, 78% with ST, and 79% with NT. Water use and water use efficiency showed non significant differences for all crops under this study on both plots with deep sub-soiling and without deep sub-soiling, suggesting that the yield differences were not significantly determined by water supply. The water use average for wheat was: 380 mm with TS, 377 mm with CS, 395 mm with DS, and 382 mm with NT. For maize, water use was 339 mm with TS, 345 mm with CS, 343 mm with DS, 341 mm with ST and 343 mm with NT. For soybean, water use was 320 mm with TS, 315 mm with CS, 317 mm with DS, 314 mm with ST and 319 mm with NT. Water use efficiency from precipitations was given for wheat, maize and soyabean. Yield increases due to deep sub-soiling were: 0.1% for wheat 1.5% for maize, and 7.3% for soybean. The average yields recorded were: For wheat 4948 kg ha -1 with TS. 4536 kg ha -1 with CS, 4814 kg ha -1 with DS, 5048 kg ha -1 with NT. For maize 8743 kg ha -1 with TS, 8954 kg ha -1 with CS, 8792 kg ha -1 with DS, 7940 kg ha -1 with ST and 9052 kg ha -1 with NT. For soybean 2098 kg ha -1 with TS, 1812 kg ha -1 with CS, 1846 kg ha -1 with DS, 1798 kg ha -1 with ST and 1941 kg ha -1 with NT. The highest yields were obtained with NT for wheat and maize. WUE was strongly correlated with yield, and had the highest values far wheat and maize with NT. In the case of soybean, we consider that a significant yield increase can be obtained with an efficient weed control and soil protection with adequate amounts of residues from the previous crop.