Normal Rainfall Conditions Research Articles

Texas Gulf Coast Soybean Yield Affected by Soybean Variety and Planting Date

Soybeans (Glycine max) are planted along the upper Texas Gulf Coast from mid-March through May to try to take advantage of early season spring and summer rains and also to complete harvest before hurricane season and fall rains become a problem. These plantings are with maturity groups (MG) IV and V and are mainly grown under nonirrigated conditions. Under normal rainfall conditions (rainfall in April, May, and early June), this study shows that a late March or early April planting date provided the highest yield although a May plant date can result in yields of greater than 50 bu/acre if rainfall is received at the proper times. However, when planting was delayed, there was a greater risk of detrimental late-season effects from drought and southern green stink bug (Nezara viridula) or the brown stink bud (Euschistus heros). In 2004 and 2005, at both locations, soybeans planted at the early plant date took longer to reach physiological maturity than the later plant dates. Generally, the earlier the plant date, the greater number of days from planting till harvest.

Estimation of suspended sediment loads and delivery in an incised upland headwater catchment, south‐eastern Australia

AbstractHistorically upland headwater catchments in south‐eastern Australia have undergone extensive gully erosion that has removed large amounts of sediment to lowlands. Recent research suggests these upland areas may continue to dominate fine sediment loads in lowland rivers. Improved understanding of sediment transfer through upland headwater catchments may have implications for interpreting downstream sediment supply. In this study a nested catchment design was utilized to examine suspended sediment yields and delivery from a small tributary sub‐catchment (1·64 km2) to the study catchment outlet (53·5 km2). Monitoring of suspended sediment concentration and discharge was undertaken for a period of nearly two years and used to estimate suspended sediment loads. Estimated total suspended sediment exports over the period of monitoring were 24·16 t from the sub‐catchment and 550·3 t from the catchment, which are generally less than previous reported small catchment yields in south‐eastern Australia. The extent of sediment delivery was examined using between‐site ratios of specific sediment yield per unit area and incised channel length. Sediment delivery was high under average rainfall conditions, but seasonally dependent. Both suspended sediment yields and the extent of delivery peaked over spring months, supplemented by remobilization of sediment stored during summer months in the main catchment channel. The findings of this study suggest much of the suspended sediment exported from small incised upland sub‐catchments (1–2 km2) may be delivered to downstream reaches under average rainfall conditions, which, in conjunction with the findings of previous research supports the potential importance of contributions from these areas to suspended sediment loads in lowland rivers during high flow periods. Copyright © 2007 John Wiley & Sons, Ltd.

Operation analysis of a reservoir in GIS environment using remote sensing inputs

Reservoir management involves allocating available water among multiple uses and users, minimizing the risks of water shortages and flooding and optimizing the beneficial use of water. Irrigation demands from a reservoir, which are generally computed by using the design cropping pattern and average rainfall conditions, may vary over the years depending on the actual cropping pattern and meteorological conditions. This study demonstrates the utility of remote sensing inputs and geographic information system (GIS) environment for determining realistic irrigation demands from a reservoir. Remote sensing data are used to map the actual cropping pattern in the command area while the GIS is used for integrating the field‐level irrigation demands up to the canal system head. Ten daily irrigation demands in the command area of Samrat Ashok Sagar Reservoir in Madhya Pradesh, India have been estimated and the reservoir operation policy has been derived. Through the simulation analysis with 29 years of inflow data, rule curves have been derived for the operation of reservoir so that water deficit (if any) can be distributed in time much in advance and severe crop failure can be avoided. Inferences drawn from the analysis can guide the system operator in using the available water in a scientific and judicious manner.

Soil physical properties and root activity in a soybean second crop/maize rotation under direct sowing and conventional tillage

Soil degradation is the result of interactions involving the soil itself, human activity, climate, relief, and vegetation. These can lead to changes in —or even the loss of— certain characteristics of the soil, reducing its present and future productive capacity. The aim of this study was to determine the behaviour of a number of soil physical variables and total organic carbon content, as well as the root activity and yield of crops grown in rotation (soybean in 1998/1999 and maize in 1999/2000) under direct sowing (DS) and conventional tillage (CT) conditions. Root activity was assessed using an isotopic methodology involving the uptake of 32P. The root activity of the soybean crop, which grew under normal rainfall conditions, was greater under CT conditions. That of the maize crop, which grew when rainfall was well below normal, was greater under DS conditions. Bulk density was higher and total porosity lower in the upper 0.10 m of the soil in the DS plots. Conventional tillage led to lower penetration resistance values in the upper layers of the soil profile. No differences in soil total organic carbon were found between the two tillage systems. The soil water content of the upper soil layers was higher under DS. The yield of the soybean crop under CT was 57% higher than under DS. The yield of maize was affected by water deficiency; higher yields were obtained with DS than with CT.

MONTHLY RUNOFF PREDICTIONS BASED ON RAINFALL FORECASTS IN A SMALL OKLAHOMA WATERSHED1

ABSTRACT: Conditions under which monthly rainfall forecasts translate into monthly runoff predictions that could support water resources planning and management activities were investigated on a small watershed in central Oklahoma. Runoff response to rainfall forecasts was simulated using the hydrologic model SWAT. Eighteen scenarios were examined that represented combinations of wet, average, and dry antecedent rainfall conditions, with wet, normal, and dry forecasted rainfall. Results suggest that for the climatic and physiographic conditions under consideration, rainfall forecasts could offer potential application opportunities in surface water resources but only under certain conditions. Pronounced wet and dry antecedent rainfall conditions were shown to have greater impact on runoff than forecasts, particularly in the first month of a forecast period. Large forecast impacts on runoff occurred under wet antecedent conditions, when the fraction of forecasted rainfall contributing to runoff was greatest. Under dry antecedent conditions, most of the forecasted rainfall was absorbed in the soil profile, with little immediate runoff response. Persistent three‐month forecasts produced stronger impacts on runoff than one‐month forecasts due to cumulative effects in the hydrologic system. Runoff response to antecedent conditions and forecasts suggest a highly asymmetric utility function for rainfall forecasts, with greatest decision‐support potential for persistent wet forecasts under wet antecedent conditions when the forecast signal is least dampened by soil‐storage effects. Under average and dry antecedent conditions, rainfall forecasts showed little potential value for practical applications in surface water resources assessments.

Supplementary weed control using soil-applied herbicides in glyphosate-resistant maize in Texas

Field studies were conducted during the 2000 and 2001 growing seasons to evaluate the effects of glyphosate with and without soil-applied herbicides on weed control and yield in Zea mays. In 2000, under above normal rainfall conditions, glyphosate used alone provided poor control of Amaranthus albus when applied early post-emergence but gave improved control when applied later in the growing season. Brachiaria platyphylla control was poor with glyphosate alone applied early post-emergence and improved when applied later in the season. In 2001, a below normal rainfall year, A. albus and B. platyphylla control were very good with all glyphosate only applications. When a soil-applied herbicide was applied pre-emergence prior to glyphosate applied post-emergence, A. albus and B. platyphylla control was greater than 85% in both years. The use of soil-applied herbicides improved the reliability of weed control in glyphosate-resistant maize.

Spatial and temporal patterns of phytoplankton composition in subtropical coastal lagoon, the Indian River Lagoon, Florida, USA

A 2 year study of the phytoplankton community was carried out in the Indian River Lagoon, USA. In terms of biovolume, the phytoplankton community was generally dominated by dinoflagellates, diatoms or cyanobacteria. Mean phytoplankton standing crops were highest in the most flow-restricted regions of the lagoon, which had the lowest mean salinity values and comparatively high total nitrogen:total phosphorus ratios. In this region, blooms of dinoflagellates were common in the first year of the study, which was characterized by an El Nino event that yielded exceptionally high rainfall levels and freshwater outflow. Picoplanktonic cyanobacteria blooms became more prominent in the second year of the study, which was characterized by below average rainfall conditions. In unrestricted flow regions of the lagoon, located near inlets to the Atlantic Ocean, diatoms were most often the dominant taxa. Regions of intermediate water turnover rates and high external loading of phosphorus had a prevalence of diatom blooms. However, the average phytoplankton standing crops in the latter regions did not reach the levels experienced in the flow-restricted parts of the lagoon. In terms of individual phytoplankton taxa, the most common bloom-forming diatoms in the Indian River Lagoon system included: Skeletonema costatum, Dactyliosolen fragilissimus, Skeletonema menzelii, Cerataulina pelagica, Odontella regia, Chaetoceros lorenzianus, Rhizosolenia setigera and Thalassionema nitzschioides. The major bloom-forming dinoflagellate species included: Pheopolykrikos hartmannii, Akashiwo sanguinea, Prorocentrum micans, the potentially toxic species Pyrodinium bahamense var. bahamense and Prorocentrum minimum. Several picoplanktonic cyanobacteria were also prominent members of the phytoplankton community, including Synechococcus elongates. The spatial and temporal patterns observed in some of these dominant species were attributable to patterns in key environmental variables, including salinity, temperature and nutrient concentrations.

Conjunctive Use of Surface and Groundwater for Coastal and Deltaic Systems

A regional conjunctive use model is developed for a near-real deltaic aquifer system, irrigated from a diversion system, with some reference to hydrogeoclimatic conditions prevalent in the east coastal deltas of India. Water resources are sufficiently available in these regions under average monsoon rainfall conditions, but their distribution in space and time has been ever challenging to water managers. Surface-water availability shows temporal fluctuations in terms of floods and droughts, and groundwater availability shows mainly spatial variability in terms of quality and quantity due to the hydrogeologic setting, boundary conditions, and aquifer properties. The combined simulation-optimization model proposed in this study is solved as a nonlinear, nonconvex combinatorial problem using a simulated annealing algorithm and an existing sharp interface model. The computational burden is managed within practical time frames by replacing the flow simulator with artificial neural networks and using efficient algorithmic guidance.

Field studies on the biological control of nematode parasites of sheep in the tropics, using the microfungus Duddingtonia flagrans

Long-term field studies were conducted on two government managed small ruminant research farms, located in different geo-climatic regions and approximately 300 km separate from each other, on Peninsula Malaysia. The Infoternak trial (48 weeks) and the Chalok trial (43 weeks) each compared nematode parasite control in separately managed groups of young sheep, either short-term rotationally grazed around a suite of 10 paddocks in addition to receiving a daily supplement of Duddingtonia flagrans spores (Fungus Group); or similar groups of sheep being rotationally grazed alone (Control Group). The prevailing weather conditions at Infoternak farm were of below average rainfall conditions for the most of the trial. As a consequence, only very low worm infections (almost exclusively Haemonchus contortus) were acquired by the 17 sets of tracer lambs that grazed sequentially with the experimental lambs. However on all except 2 occasions in the early part of the trial, the mean tracer worm burdens were significantly lower ( P<0.05) and the experimental lambs grew significantly better ( P=0.054) in the Fungus Group. Rainfall at Chalok farm during the course of the trial was also below average. As a consequence infectivity of pastures was assumed to be relatively low based on faecal egg counts (epg) of the experimental sheep, which following an anthelmintic treatment prior to allocation, remained very low in both treatment groups. Faecal egg counts of undosed replacement lambs in the latter half of the Chalok study, showed a progressive increase in the Control Group to levels exceeding 3000 epg, whereas the Fungus Group remained static at approximately 500 epg. These results show that the deployment of the nematophagous fungus, D. flagrans, can improve the level of parasite control of sheep in the tropics above that which can be achieved by the short-term rotational grazing strategy alone.

Volume de enxurrada e perda de solo em estradas florestais em condições de chuva natural

Foram determinados o volume total de água escoada e a perda de solo através da produção de sedimentos provenientes de segmentos de estradas florestais em condições de chuva natural, com diferentes valores de precipitações. As inclinações dos segmentos de 1 e 7% foram analisadas, enquanto os comprimentos variaram de 20 e 40 m, com 4 m de largura. Os segmentos de estrada foram delimitados com tábuas de 0,30 m de largura, envolvidas em lona plástica, para sua impermeabilização. Os dados de volume e intensidade de precipitação diária foram obtidos com a instalação de pluviômetro e pluviógrafo no local. O período de coleta de dados foi de um ano, concentrando-se na época das chuvas. O volume de enxurrada foi mais afetado pelo comprimento do segmento, ao passo que a massa de solo sofreu maior influência da declividade. A massa de solo erosinado cresceu exponencialmente em função do incremento do volume de enxurrada.

Forecasting, warning, and detection of malaria epidemics: a case study

Our aim was to assess whether a combination of seasonal climate forecasts, monitoring of meteorological conditions, and early detection of cases could have helped to prevent the 2002 malaria emergency in the highlands of western Kenya. Seasonal climate forecasts did not anticipate the heavy rainfall. Rainfall data gave timely and reliable early warnings; but monthly surveillance of malaria out-patients gave no effective alarm, though it did help to confirm that normal rainfall conditions in Kisii Central and Gucha led to typical resurgent outbreaks whereas exceptional rainfall in Nandi and Kericho led to true malaria epidemics. Management of malaria in the highlands, including improved planning for the annual resurgent outbreak, augmented by simple central nationwide early warning, represents a feasible strategy for increasing epidemic preparedness in Kenya.

Mathematical model for the analysis of irrigation water and fertilizer management for spring wheat in the semiarid area of West Liaoning, China

An experiment with a D-optimum saturation design (D-312) of three factors (N, P fertilizers and irrigation water) and five levels was used to assess the combined effects of N, P fertilization and irrigation water on the grain yield of spring wheat grown in the semiarid area of West Liaoning province, P. R. China. Best-fit predictive model of spring wheat grain yield was constructed by simultaneously including these three factors. The effects of N, P fertilizers and irrigation water on spring wheat grain yield were highly statistically significant. Although a previous study in the same area had shown that water was the most important factor affecting spring wheat grain yield, principal factor analysis in this experimental case indicated that, under normal rainfall conditions when the amount of irrigation water ranged from 45 to 360 mm, N fertilizer was the most effective factor, while marginal effect analysis demonstrated that the spring wheat grain yield response to N, P fertilizers and irrigation water met the law of diminishing returns. Increasing P fertilizer levels enabled to enhance the ability of spring wheat to tolerate drought during the period of water shortage. The most economic allocation of N, P, and irrigation water for 5,794 kg ha−1 spring wheat grain yield was 214.4 kg N ha−1, 37.5 kg P ha−1, and 349.6 mm of irrigation water. Optimum allocation of water and fertilizers not only increased the water use efficiency for spring wheat, but also enhanced the recovery of applied fertilizers.

Intra‐seasonal rainfall characteristics and their importance to the seasonal prediction problem

AbstractDaily station rainfall data in South Africa from 1936 to 1999 are combined into homogeneous rainfall regions using Ward's clustering method. Various rainfall characteristics are calculated for the summer season, defined as December to February. These include seasonal rainfall total, region‐average number of station rain days exceeding 1 and 20 mm, region‐average of periods between rain days at stations &gt;1 and &gt;20 mm, region‐average of wet spell length (sequential days of station rainfall &gt;1 and &gt;20 mm), correlation of daily station rainfall within a region and correlation of seasonal station rainfall anomalies within a region.Rank‐ordered rainfall characteristic data generally form an s‐shaped curve, and significance testing of discontinuities in these curves suggests that normal rainfall conditions in South Africa consist of a combined middle three quintiles separated from the outer quintiles, rather than the traditional middle tercile.The relationships between the various rainfall characteristics show that seasons with a high total rainfall generally have a higher number of heavy rain days (&gt;20 mm) and not necessarily an increase in light rain days. The length of the period between rain days has a low correlation to season totals, demonstrating that seasons with a high total rainfall may still contain prolonged dry periods. These additional rainfall characteristics are important to end‐users, and the analysis undertaken here offers a valuable starting point for seeking physical relationships between rainfall characteristics and the general circulation. Preliminary studies show that the vertical mean wind is related to rainfall characteristics in South Africa. Given that general circulation models capture this part of the circulation adequately, seasonal forecasts of rainfall characteristics become plausible. Copyright © 2002 Royal Meteorological Society.

Enteric viruses in drinking water supplies

Two rural spring drinking water supplies were studied for their enteric virus levels. In one, serving about 30 dwellings, the water was chlorinated before distribution; in the other, which served a dairy and six dwellings the water was not treated. Samples of treated (40 l) and untreated (20 l) water were taken under normal and heavy rainfall conditions over a six weeks period and concentrated by adsorption/elution and organic flocculation. Infectious enterovirus in concentrates was detected in liquid culture and enumerated by plaque assay, both in BGM cells, and concentrates were also analysed by RT-PCR. Viruses were found in both raw water supplies. Rural supplies need to be analysed for viruses as well as bacterial and protozoan pathogens if the full microbial hazard is to be determined.

Site-specific evaluation of the CROPGRO-soybean model on Missouri claypan soils

Crop yield is affected by many factors, primarily encompassing soil and weather conditions, and crop management practices. Crop modeling can be used to help understand how multiple factors interact and impact yield. The CROPGRO modeling package has been used extensively to assess the effects of management practices and environmental conditions on soybean growth and development. However, the model has not been thoroughly evaluated for some environments that have unique characteristics such as claypan soils in which the depth to the claypan horizon can vary greatly within fields. The objectives of this study were to evaluate the performance of the CROPGRO-Soybean model for simulating site-specific crop growth, soil water content, and grain yield on claypan soils. Data were obtained during low and average rainfall conditions from two sites over 3 years in central Missouri. Plant (e.g. yield, leaf area, root length density) and soil (e.g. topsoil thickness, moisture, texture) measurements were collected for calibrating and validating the model. Results indicated that CROPGRO-simulated soil water contents in the 15–90 cm soil profile agreed well with measured values. Simulated leaf area index and grain yield also agreed well with measured values during average precipitation years, but were under-estimated during extremely dry years. Within-season precipitation and claypan soil topsoil depth were shown to have greatest influence on soybean yield. Although we hypothesized it to be otherwise, field measurements in 1997 showed that the claypan did not negatively affect soybean root penetration.

Modelling the effects of drought on the population of brown trout in Black Brows Beck

Records from a 30-year study of the population of migratory brown trout, Salmo trutta L., in Black Brows Beck (English Lake District) are used to construct a model for predicting population numbers during normal rainfall conditions and under the influence of drought. Twice-yearly samples of different age-groups of trout were recorded, together with a more detailed set of records for a further 8 years. These data are used to develop and calibrate a time-dependent population model. A concurrent record of rainfall data for Windermere is aggregated to form seasonal averages and used as an indicator of drought for the region. Drought conditions result in lower than expected stock which can be identified as outliers from the Ricker stock-recruitment curves for each sample. A set of five difference equations, which describe the overlapping trout age-groups, is identified and used to forecast the trout population up to a few years ahead. The model is particularly successful at forecasting population numbers 1-year ahead if the following years drought is taken into account. Incorporation of drought effects into the model significantly improves model forecasts. A linearised stability analysis suggests that long-term drought conditions will have the effect of increasing population stability, although a particularly severe drought, or series of severe droughts, may lead to population decline.

Water balance study and conjunctive water use planning in an irrigation canal command area: A remote sensing perspective

Water budgeting of the D-36 and D-36 A distributaries confined between Pedda Vagu, Korutla Vagu and Kakatiya main canal of the Sri RamSagar Project (SRSP) Command area was conducted using remote sensing derived crop areas, land cover information, irrigation tank inventory and source-wise distribution of irrigated areas, together with conventional meteorological, canal flows and well inventory data. A semi-empirical water balance model was developed and validated using remote sensing derived objective information of the command area and the validated model used for predicting the groundwater table under normal rainfall conditions. Recharge and water balance in the study area indicated that the net recharge to the aquifer is negative to the tune of 2.54 Mm3 resulting in a fall of the groundwater table by 0.79 m during 1992-93. However, normalized groundwater recharge and water balance estimates indicate an impending waterlogging problem with an annual groundwater table rise of 0.35 m. In view of existing water management practices, a conjunctive water use plan of rotational operation of aquifers and canals is suggested.

Degradation of sodium monofluoroacetate (1080) in buried fox baits

The degradation of 1080 in buried Foxoff® baits was investigated. Baits were exposed to 5 different treatments: shelf-stored controls, prevailing weather, no rainfall, average weekly rainfall and twice average weekly rainfall. Curvilinear regression models were used to model the rates of decay of 1080. These predicted that under normal rainfall conditions, baits would become non-lethal to working dogs at 2.2 weeks and foxes at 2.8 weeks. Management implications of these results are discussed.

Corn Yield, Runoff, and Sediment Losses from Manure and Tillage Systems

AbstractOne challenge in land application of manure is to maximize its benefit to crops without harming the environment. Our objective was to evaluate the impact of manure addition on corn yield, and sediment losses in snowmelt and rainfall runoff under moldboard plow (MP) and ridge tillage (RT) systems. Corn (Zea mays L.) grain yield and sediment losses in surface runoff after a one‐time spring application of (16.2 dry Mg ha−1) solid beef (Bos taurus) manure on a 12% slope Forman (fine‐loamy, mixed Udic Argiborolls)‐Buse (fine‐loamy, mixed Udorthentic Haploborolls) complex were measured from 1992 through 1994. In 1993, there was no effect of manure on grain yield irrespective of tillage because of high rainfall. Under average rainfall conditions in 1994, grain yield (10.2 Mg ha−1) in the manure RT treatment was 1.0, 0.9, and 0.7 Mg ha−1 greater than that in no‐manure RT, manure MP, and no‐manure MP treatments, respectively. Snowmelt runoff was not affected by manure application and it transported &lt;0.1 Mg sediment ha−1. Manure reduced rainfall runoff by 10 mm in 1993 and 3.2 mm in 1994, which led to reduction in sediment loss of 2.5 and 0.2 Mg ha−1, respectively. The RT system resulted in lower rainfall runoff compared with the MP system for all 3 yr. Onetime manure application reduced rainfall runoff and associated sediment loss in both tillage systems. However, manure application was more effective in minimizing runoff and sediment losses during intense rainfall in the RT than in the MP system.

A statistical method for evaluating the effects of antecedent rainfall upon runoff: applications to the coastal plain of Georgia

A statistical (hypothesis testing) method is described for analysing the effects of long-term (1 year) antecedent rainfall upon subsequent runoff. This method which is regional, rather than stream-specific, was applied to the southeastern US coastal plain in Georgia for the study period 1948–1994. Three sets of forty 12 month periods were used to classify antecedent rainfall into three populations: “high” (+15 to +59% normal), “low” (−11 to −42% normal), and “normal” (−9 to +8% normal). These groups were then interrelated with three groups of “subsequent” rainfall, subdivided upon a similar basis. This resulted in the creation of nine unique sub–populations consisting of combinations of antecedent and subsequent periods. Subsequent periods of 3, 6, 12, and 24 months were used. A “production ratio” (runoff/rainfall) was defined for each subsequent period and then normalized with the long-term (47 year study period) average production ratio for those months. The nonparametric Wilcoxon–Mann–Whitney test was used to evaluate differences between mean normalized production ratios for the nine subpopulations. The results of a critical hypothesis test revealed that production ratios return to normal between 1 and 2 years following a drought, given a return to normal rainfall conditions. This might represent the time required for contributions to streamflow from local ground-water flow systems to return to normal following a drought. Production ratios associated with “high” antecedent rainfall remain considerably greater than normal for a period of at least 2 years following a return to normal rainfall.