Hot Dry Months Research Articles

Seasonal changes in semen characteristics of pure and crossbred rabbit bucks fed graded levels of vitamin C under heat stress conditions

The experiment was carried out to investigate the effect of season and graded vitamin C levels on semen quality of rabbit bucks in the Northern Guinea Savanna of Nigeria. A total of 55 rabbit bucks consisting of 40 pure New Zealand White (NZW) and 15 New Zealand x California (NZW×CAL) crossbreds were used for the study. The duration of the study spanned the hot dry (March-May) and cool wet (June-August) seasons. The traits investigated were semen motility, concentration, volume, pH, colour, live and dead sperm. Results obtained showed that vitamin C had significant (p<0.01) effect on semen characteristics. There was a progressive increase in semen motility, concentration and live sperm and decrease in dead sperm as vitamin C level increased. Semen volume deviated from this pattern while colour was consistent all through. The result on monthly variation indicated that volume increased during the months of March to May ranging between 1.32-1.43 ml while during the months of June to August, it oscillated between 0.41 - 0.95 ml. Sperm concentration significantly (p<0.05) increased from the hot dry months (75.72-129.48x106) to the cool wet months (98.17-102.78x106) while colour remained consistent with an increase in live sperm cells. There was significant (p<0.001) interaction between vitamin C level and season on sperm motility, concentration and live sperm being better in the hot dry (70.9%, 114.5x106, 85.31%) and cool wet (76.3%, 121.6x106, 90.14%) seasons on 400 mg/kg feed vitamin C. Sperm volume was higher on 100 mg/kg feed vitamin C in the hot dry (1.60 ml) and cool wet (0.98 ml) seasons and 400 mg/kg feed in the hot dry (1.57 ml) and cool wet (0.77 ml) than other levels. Based on the results, it is concluded that vitamin C improved the semen characteristics of rabbit bucks at 400 mg/kg feed during the hot dry season which translates to improved semen quality.

Thermal comfort evaluation in architectural studio classrooms – A summer study in a warm to moderate Indian climate

This paper reports the findings from a thermal comfort field study conducted in institutional studio classrooms in the warm-to-moderate climate of Tumkur in Karnataka, India. A total of 506 datasets were obtained in the questionnaire survey consisting of students of architecture. The survey was carried out during the hot-dry months of March, April and May 2019 using subjective questionnaires during which indoor environment variables were measured simultaneously in accordance with ASHRAE Standard 55 Class II protocols. A comfort temperature of 30.4°C was obtained using Griffith’s method, and the comfort band was found to be between 25.0°C to 32.5°C on the central sensation scale for 80% acceptability for the summer (hot-dry) season. Subjects showed greater tolerance and adaptation to warmer conditions with the main means of adaptation by opening windows, wearing lighter clothing, use of ceiling fans, drinking of cold water and use of curtain blinds. Comparison of the field study results with international standards shows that the standards failed to capture the comfort limits and adaptations of subjects in tropical climates of India. Findings of the present study bear significance in developing guidelines for thermal comfort for institutional buildings in the warm-to-moderate climate of India.

Variation in ground insect diversity, composition and abundance across land use types in an African savanna, Zimbabwe

Fragmentation of African savannas into such ecosystems as grazing land, woodland, fallow land and cropping land has deleterious effects on soil insect biodiversity. Soil insects are sensitive indicators of habitat fragmentation. They form an integral ecosystem functional component. As such, they are critical in ecosystem functioning. Pitfall traps were used to assess insect diversity, composition and abundance in four land use types (fallow, grazing, woodland and cropping) in an African savanna during months of February to October 2017. Pitfall traps were set up monthly in the four land use categories over a period of 7 days. Insects were collected twice every three days and counted and identified. Redundancy Analysis (CANOCO version 6.5) was used to determine soil characteristics that influenced insect community dynamics. A total of 2,138 insects from seven orders, 14 families, 48 genera and 57 species were collected. Orders Hymenoptera (46.46%) and Coleoptera (36.20%) comprised the dominant taxa across all land use types irrespective of season. The most dominant families were Formicidae (46.46%) and Tenebrionidae (27.19%) whose species occurred frequently across the four land use types. The carpenter ant, Camponotus maculatus, and the beetle, Zophosis boei, were the most abundant and dominant species in all land use types and occurred across the sampling period, being most abundant during the hot dry months. Highest insect abundances were recorded during the hot dry months, with grazing land recording the highest abundance (656) and woodland the lowest (418). The main difference among land use types was a seasonal shift in insect species associated with C. maculatus and Z. boei. Two assemblages comprising of sites from (i) woodland and cropping land were dominated by coleopteran species and (ii) fallow and grazing land by hymenopteran species mixed to a lesser extent with coleopteran species. Soil moisture, phosphorous, pH and initial nitrogen content were identified as influential variables in ground insect community dynamics (F ratio = 1.928, p = 0.002). Ground insect community dynamics was driven by the effect of land use on edaphic factors and season. The observation that a distinct soil insect community occurred in each land use category as a variant of seasonal associations with C. maculatus and Z. boe sets a basis for using ground insects as potential indicators of the impact of land use which contributes to the understanding and identification of indicators involved in adequate conservation and management.

Diverse biosphere influence on carbon and heat in mixed urban Mediterranean landscape revealed by high resolution thermal and optical remote sensing

A fundamental challenge in verifying urban CO2 emissions reductions is estimating the biological influence that can confound emission source attribution across heterogeneous and diverse landscapes. Recent work using atmospheric radiocarbon revealed a substantial seasonal influence of the managed urban biosphere on regional carbon budgets in the Los Angeles megacity, but lacked spatially explicit attribution of the diverse biological influences needed for flux quantification and decision making. New high-resolution maps of land cover (0.6 m) and irrigation (30 m) derived from optical and thermal sensors can simultaneously resolve landscape influences related to vegetation type (tree, grass, shrub), land use, and fragmentation needed to accurately quantify biological influences on CO2 exchange in complex urban environments. We integrate these maps with the Urban Vegetation Photosynthesis and Respiration Model (UrbanVPRM) to quantify spatial and seasonal variability in gross primary production (GPP) across urban and non-urban regions of Southern California Air Basin (SoCAB). Results show that land use and landscape fragmentation have a significant influence on urban GPP and canopy temperature within the water-limited Mediterranean SoCAB climate. Irrigated vegetation accounts for 31% of urban GPP, driven by turfgrass, and is more productive (1.7 vs 0.9 μmol m−2 s−1) and cooler (2.2 ± 0.5 K) than non-irrigated vegetation during hot dry summer months. Fragmented landscapes, representing mostly vegetated urban greenspaces, account for 50% of urban GPP. Cooling from irrigation alleviates strong warming along greenspace edges within 100 m of impervious surfaces, and increases GPP by a factor of two, compared to non-irrigated edges. Finally, we note that non-irrigated shrubs are typically more productive than non-irrigated trees and grass, and equally productive as irrigated vegetation. These results imply a potential water savings benefit of urban shrubs, but more work is needed to understand carbon vs water usage tradeoffs of managed vs unmanaged vegetation.

Spatiotemporal Distributions of Sheep and Goat Pox Disease Outbreaks in the Period 2013-2019 in Eastern Amhara Region, Ethiopia.

Sheep and goat pox is highly contagious viral infection of sheep and goats caused by the genus Capripox virus. Clinically, the disease is characterized by fever, macules developing into papules, and necrotic lesions in the skin and nodular lesions in internal organs. In Ethiopia, there are seroprevalence epidemiological studies on the disease. However, the spatiotemporal clustering of sheep and goat pox incidence has not been investigated. A retrospective study design using the outbreak reported data from Kombolcha Regional Laboratory for the years from September 2013 to December 2019 was performed to determine the temporal and spatial distribution of sheep and goat pox outbreaks. A total of 663 sheep and goat pox disease outbreaks were reported in all major parts of Eastern Amhara region between 2013 and 2019. In this period, sheep and goat pox was reported in all administrative zones of Eastern Amhara region (n = 5). The average incidence of sheep and goat pox outbreaks at the district level was 8.61 per 7 years. The incidence differed between areas, being the lowest in hot dry month and highest in warm and cold moist months. Sheep and goat pox outbreaks generally have a peak in November followed by August and a low in May. There is a significant difference in the occurrence of sheep and goat pox disease outbreaks between months and years (p < 0.001). The forecast for the period 2020–2026 revealed that a high number of sheep and goat pox disease outbreaks will occur than the previous one. Therefore, all stakeholders should work cooperatively to combat this disease occurrence, and there should be capacity development for participatory disease search, risk analysis, laboratory diagnosis, and information management in order to respond properly to outbreak of sheep and goat pox disease; thereby, it enhances the prevention and control the disease.

Epidemiology of acute rubella infection in Zambia during the pre-vaccination period (2005\u20132016) as a baseline for monitoring rubella epidemiology in the post-rubella vaccine introduction era

BackgroundRubella is highly under reported in Zambia as in most sub-Saharan countries despite being a disease of major public health concern especially among women of childbearing age. In September 2016, Zambia introduced a combined measles-rubella vaccine in children 0–14 years. In this study, we estimated the proportion positive for acute rubella among suspected but negative measles cases between 2005 and 2016 and determined its correlates for monitoring rubella epidemiology post-rubella vaccine introduction.MethodsIn a retrospective study, 4497 measles IgM negative serum samples from 5686 clinically suspected measles cases were examined for rubella IgM antibodies using the Siemens, Enzygnost® ELISA kit at the national measles laboratory. Data on demographics, year and month of onset were extracted from the surveillance data. Multivariate logistic regression analysis using backward variable selection was conducted to determine independent predictors for acute rubella. The magnitude of association was estimated using adjusted odds ratio with a 95% confidence interval.ResultsOverall, a proportion of 29.2% (1313/4497) affecting mostly those between 5 and 24 years was determined. Only age, province, month and year were independently associated with acute rubella. The regional proportions varied from 21.8–37.3% peaking in the month of October. Persons in the age group 10–14 years (Adjusted Odds Ratio [AOR] = 2.43; 95% CI [2.01–2.95]) were more likely while those aged < 1 year less likely (AOR = 0.31; 95% CI [021–0.48]) to have acute rubella compared to those aged 25 years or older. Persons in 2010 were less likely (AOR = 0.12; CI [0.05, 0.28]) to have acute rubella compared to those in 2016. While acute rubella was more likely to occur between July and November compared to December, it was less likely to occur between February and May.ConclusionsRubella virus was circulating in Zambia between 2005 and 2016 affecting mostly persons in the age group 5–24 years peaking in the hot dry season month of October. Although vaccination against rubella has been launched, these baseline data are important to provide a reference point when determining the impact of the vaccination program implemented.

Effectiveness of various cooling systems during high environmental temperature on production and welfare indices of laying pullets in deep litter system of rearing

The present study was conducted to determine the effect of different cooling systems; Fan Fogger (FF) and Fan Pad (FP) on micro environment of poultry house, thermal comfort, welfare, egg production and egg quality parameters of laying hens. This experiment was conducted on 210, White Leghorn laying pullets (32 weeks old) during hot-dry summer months (May - July) under deep litter system of housing. The FP and FF cooling systems significantly dropped the mean shed temperature and increased the relative humidity. Thus, better THI resulted in increase in egg production by 4.66 % and 3.32 % under FP and FF systems over the control group. However, specific gravity, H.U, egg shell thickness, yolk index and yolk color were not significantly influenced by cooling treatments. Significantly lower levels of antioxidant enzymes viz. LPO, Catalase, G6PD, GPx and SOD was registered in cooling groups. Both the cooling devices contributed towards bird welfare by altering the behavioral expression from agonistic to non-agonistic activities.

Different ambient management intervention techniques and their effect on milk production and physiological parameters of lactating NiliRavi buffaloes during hot dry summer of subtropical region.

In tropical countries, one of the major threats for diary animal production is climate change. Ambient management interventions are beneficial and are the dire need of animal production in tropics. Ambient management intervention and its effect on physiological performance of lactating NiliRavi buffaloes were investigated during the hot dry months (April to June) of Pakistan. Fifteen lactating NiliRavi water buffaloes of similar size, age, and same parity were randomly stratified into three groups, comprising of five animals in each group, designated as group S, SF, and SFS. Animals of group S (control) were kept just under the shade while the animals in group SF were provided shade plus fan, animals in group SFS were provided the shade, fan as well as sprinklers during the hot day hours between 10:00AM to 6:00PM. Shed conditions were same for all animals, isonitrogenous and isocaloric feed was provided to all animals. Milk production decreased with the increase in ambient temperature. Average dry matter intake in group S, SF, and SFS were 75%, 80%, and 90% of the total feed offered to the experimental animals, respectively. The mean rectal temperatures (°F) were 101.69, 101.19, and 100.85 in group S, SF, and SFS, respectively. Heat stress had pronounced effect on blood glucose level as indicated by the mean glucose concentration in group S and SFS being recorded at 78.04mg/dl and 90.47mg/dl, respectively. It is concluded that the buffaloes should be provided with sprinklers and fans to minimize heat load and maximize the production during hot dry season.

Behavioural and Well Being Comparison of Broiler Chicks in the Different Cooling Regime during Hot-Dry and Hot-Humid Months of summer

Behavioural and Well Being Comparison of Broiler Chicks in the Different Cooling Regime during Hot-Dry and Hot-Humid Months of summer

Effect of misting and wallowing cooling systems on milk yield, blood and physiological variables during heat stress in lactating Murrah buffalo.

BackgroundHeat stress adversely affects the physiological and metabolic status, and the productive performance of buffalo.MethodsThe present study was conducted to explicate the effect of misting and wallowing cooling strategies during heat stress in lactating Murrah buffalo. The study was conducted for three months (May–July) of which first two months were hot dry and last month was hot humid. Eighteen lactating buffaloes, offered the same basal diet, were blocked by days in milk, milk yield and parity, and then randomly allocated to three treatments: negative control (no cooling), cooling by misting, and cooling by wallowing.ResultsThe results showed higher (P < 0.05) milk yield in buffaloes of misting and wallowing group compared to control during the experimental period however wallowing was found more (P < 0.05) effective during July (hot humid period). Both the treatments resulted into significant (P < 0.05) reduction in rectal temperature (RT) and respiratory rate (RR) compared to control animals during study period whereas wallowing was found to be effective on pulse rate (PR) only during July. Both treatments were resulted in mitigating the heat stress mediated decrease in packed cell volume (PCV), lymphocytopnoea and neutrophilia whereas decrease in total erythrocyte count (TEC) and monocytes was only mitigated by wallowing. Heat load induced alteration in serum creatinine and sodium concentration was significantly (P < 0.05) ameliorated by misting and wallowing whereas aspartate aminotransferase, alkaline phosphatase and superoxide dismutase activity, and reactive oxygen species concentration could be normalized neither by misting nor by wallowing. The significant (P < 0.05) increment in serum cortisol and prolactin levels observed in June and July period in control animals was significantly (P < 0.05) prevented by misting and wallowing.ConclusionsIt can be concluded that misting and wallowing were equally effective in May and June (hot dry period) whereas wallowing was more effective during hot humid period in preventing a decline in milk production and maintaining physiological, metabolic, endocrine and redox homeostasis.

Cacti supply limited nutrients to a desert rodent community.

In the Sonoran Desert, cacti represent a potentially important source of nutrients and water for consumers. Columnar cacti, in particular, produce a large pulse of flowers and succulent fruit during hot summer months. The importance of cactus stems, flowers and fruit to the small mammal community has not been quantified. We exploited natural variation in the carbon isotope (δ(13)C) values of cacti (CAM) versus C3 plants to quantify the relative use of these resources by a diverse desert small mammal community. We also estimated trophic level by measuring nitrogen isotope (δ(15)N) values. We hypothesized that (H1) granivorous heteromyids (kangaroo rats, pocket mice) would exploit the summer pulse of seeds and pulp; (H2) folivorous and omnivorous cactus mice, wood rats, and ground squirrels would exploit cacti stems year-round and seeds when available; and (H3) kangaroo rats and pocket mice would shift from seeds to insects during hot dry months. We found that heteromyids made minimal use of seeds during the period of heavy seed rain. Of the cricetids, only the folivore Neotoma albigula made continuous but highly variable use of cacti resources (annual mean = 32%, range 0-81%), whereas the omnivore Peromyscus eremicus ignored cacti except during the summer, when it exploited seeds and/or fruit pulp (June-July mean = 39%, range 20-64%). We also found little evidence for a shift to greater consumption of insects by heteromyids during the hot dry months. Overall, use of cactus resources by the small mammal community is very limited and highly variable among species.

The relationship between total solar radiation and biologically erythematic radiation over urban region of Egypt

Abstract This work studies the relationship between the effective of erythematic radiation (EER) and the total solar radiation ( G ) from urban region of Egypt. The measurements of total solar radiation ( G ) and biologically effective erythematic radiation (EER) incident on a horizontal surface at Cairo, Egypt (lat. 30°05′N and Long. 31°15′E), during the period time (1990–2010) are used. The relationship between hourly mean and daily mean of EER and the hourly mean daily mean totals of broadband total solar radiation is presented. The average hourly monthly mean variation of slant ozone Z and UVB transmission K tUVB at the present work are found. The relation between the two variables slant ozone Z and UVB transmission K tUVB show an opposite seasonal behavior, the low values of the slant ozone column during summer time produce high UVB transmission values in this season. The apposite pattern is observed during the winter. The Seasonal Statistical values of regression equations; the slopes ( β ), intercepts ( α ) and the standard errors (SE) for the fitted lines. The minimum slope occurs in winter, indicating that the percentage reduction in EER at higher SZA is larger than G . The variations of the slopes ( β ) during the course of the year ranges from a minimum of 0.2214 in winter to a maximum of 0.2914 in summer, the intercepts also show their minimum and maximum values in cold humid and hot dry months. The temporal variability of the percentage ratio of the total hourly mean daily erythema to total hourly mean daily broadband solar global irradiation (EER/ G ) is presented. The estimated values of UVB solar radiation a good agreement with the measured values of the UVB solar radiation, the difference between the estimated and measured values of UVB solar radiation varies from 2.3% to 3.6%.

Retrospective Study of Cryptosporidiosis Among Diarrhoeic Children in the Arid Region of North‐Eastern Nigeria

A retrospective study was carried out to investigate the prevalence of Cryptosporidium oocysts among diarrhoeic children (n = 650), aged between 0 and 15 years, living in Maiduguri metropolis (n = 220), Bama local government area (n = 278) and Gwoza local government area (n = 152). Stool samples were concentrated using the ethyl acetate sedimentation method. Data of stool samples with Cryptosporidium oocysts from patients within the specified age groups were collected and analysed. The overall prevalence was 42.9%. The prevalence was higher in Maiduguri metropolis 45.0%, which is an urban area as compared to Gwoza and Bama combined together 41.8% which are rural areas but not statistically significant at 95% confidence level (P > 0.05; OR = 1.14; CI = 0.82, 1.58). According to age, the prevalence in age group A (0-10 years) was higher (46.8%) as compared to age group B (11 < 15 years), which was 20.8%, and this was statistically significant at 95% confidence level (P < 0.05; OR = 3.34; CI = 1.98, 5.61). According to gender, males showed a higher prevalence (52.5%) compared with females (47.5%), but this was not statistically significant at 95% confidence level (P > 0.05; OR = 1.13; CI = 0.82, 1.53). Seasonal prevalence showed that hot dry months of March and April were higher compared with other months. Our findings indicate the presence of the pathogen in children in Borno State, Nigeria, with higher odds of the infection in younger children, and dry months may be more associated with the infection. Control and preventive measures should be taken to protect younger children from the infection.

Flock dynamics, body condition and weight variation in sheep in two ecologically different resource-poor communal farming systems

The flock dynamics and body conditions of sheep in two ecologically different communal areas were determined. Twenty-one and 15 randomly selected sheep farmers were monitored for 12 months in Gaga (sweetveld) and Sompondo (sourveld) communal areas, respectively. Sheep production potential (SPP) (P<0.05) differed between the two areas. Sheep production efficiency (SPE) was affected (P<0.05) by season and flock size. Large flocks had higher SPE values than small flocks. The SPE ranged from 1.1±0.19 in April to 1.6±0.19 in December. Total entrances for each flock were higher (P<0.05) in the hot-dry months and the hot-wet months. Most of the lambs were born in the hot-dry season and the cool-dry season. High lamb mortalities were experienced in the post-rainy and hot-wet months. Foot-rot, gall sickness and heart water were the main causes of death of ewes across the two villages. Theft, road accidents and predation were also reported for both lambs and adult sheep in the two villages. Sheep in the sweetveld had higher body weight and condition scores than those in the sourveld. The SPP and SPE were better in the sweetveld than in the sourveld.

A Retrospective Study of Cryptosporidial Diarrhea in a Region with High HIV Prevalence

This retrospective study describes 63 patients <18 years of age presenting with cryptosporidial diarrhea to Tygerberg Children's' Hospital, a referral centre in the Western Cape, South Africa, from June 2004 through May 2005. Their mean age was 18.7 months (SD 17 months). Of the patients, 39 (62%) were male and 13 (20.6%) were HIV infected. Most children (57%) presented during the hot dry months of the year (December to March) and the majority (75%) of them required hospitalization. HIV-infected children were hospitalized for longer duration (median 18 days) than HIV-uninfected children (median 8.5 days). Four HIV-infected children (30.7%) died vs. four who were either HIV uninfected or of unknown status (p = 0.049). Seven of the children who died were malnourished. The CD4 count of HIV-infected children who died was 416 × 10⁹) l⁻¹ compared with 1269 × 10⁹ l⁻¹ (p = 0.1) for uninfected children. Cryptosporidium is an important cause of diarrhea among younger children in the Western Cape, which occurs more frequently during the dry months of the year and has a worse outcome in HIV-infected children.

Influence of environmental factors on germination of Plasmopara viticola sporangia sourced from mediterranean Western Australia

Direct germination via the production of a germ tube was demonstrated in the absence of the host for Plasmopara viticola (causal agent of grape downy mildew) sporangia sourced from a major grape production area in mediterranean Western Australia (WA). In general, direct germination was favoured by environmental conditions considered less than optimal for infection by P. viticola. Most notable however was that sporangia had the capacity to germinate in the absence of free water, a factor known to be essential for the production and release of zoospores. The frequency of direct germination was low with only seven among 108 000 sporangia observed producing a germ tube. This is the first study to i) examine the influence of environmental factors viz: temperature, relative humidity (RH) and light, on the direct germination of P. viticola sporangia and ii) establish the frequency of this event. The infectivity of directly germinated P. viticola sporangia however remains unknown. Although rare, the capacity of sporangia to germinate directly and potentially infect the host, most likely when conditions are not conducive for zoospore production or survival, may provide an explanation for the source of the disease during the predominantly hot dry summer months in WA and other climatically similar viticultural areas.

Evaluation of a mass distribution programme for fine‐mesh impregnated bednets against visceral leishmaniasis in eastern Sudan

During an epidemic of visceral leishmaniasis (VL) in eastern Sudan, Médecins Sans Frontières distributed 357,000 insecticide-treated bednets (ITN) to 155 affected villages between May 1999 and March 2001. To estimate the protective effect of the ITN, we evaluated coverage and use of ITN, and analysed VL incidence by village from March 1996 to June 2002. We provided ITN to 94% of the individuals >5 years old. Two years later, 44% (95% CI 39-48%) of nets were reasonably intact. Because ITN were mainly used as protection against nuisance mosquitoes, bednet use during the VL transmission season ranged from <10% during the hot dry months to 55% during the beginning of the rainy season. ITN were put up from 9 to 11 p.m., leaving children unprotected during a significant period of sandfly-biting hours after sunset. Regression analysis of incidence data from 114 villages demonstrated a significant reduction of VL by village and month following ITN provision. The greatest effect was 17-20 months post-intervention, with VL cases reduced by 59% (95% CI: 25-78%). An estimated 1060 VL cases were prevented between June 1999 and January 2001, a mean protective effect of 27%. Although results need to be interpreted with caution, this analysis indicates a potentially strong reduction in VL incidence following a community distribution of ITN. The effectiveness of ITN depends on behavioural factors, which differ between communities.

Response of soyabean (&lt;I&gt;Glycine max&lt;/I&gt; Mer.) to wheat straw mulching in different cropping seasons

. The favoured temperature range for soyabean seed germination is 25–30 °C and the crop is sensitive to water stress. In northern India, the crop is sown in the hot-dry months of May–June. Straw mulching can alter the soil's hydrothermal regime by lowering the temperature and reducing evaporation losses. A field experiment was conducted from 1999 to 2002 at the Research Farm of Punjab Agricultural University, Ludhiana on a loamy sand soil to evaluate the effect of wheat straw mulch on soil temperature, soyabean seed yield and crop growth. Maximum soil temperatures at sowing depth, recorded during the 1-month period after sowing (seed germination to seedling establishment stage), were high under no-mulch, ranging from 30.6 to 48.6 °C, while mulching substantially reduced these temperatures by 1.4 to 12.7 °C. Mulching increased soyabean seed yield by 4.4 to 68.3% in different cropping seasons; it also increased plant biomass by 17 to 122% and nodule mass by 8 to 220%. Leaf area index, chlorophyll content of leaves and number of pods per plant were all increased. Seed yield improvement under mulch was negatively correlated with rainfall distribution (number of rainy days) and amount during the whole cropping season. The percentage increase in seed yield with mulching was regressed against the total number of rainy days and total rainfall in millimetres in the cropping season. Thereby 93% of the variation in response to mulching in different cropping seasons was explained by the distribution and amount of rainfall.

Adaptation of olive (Olea europaea L.) to water-limited environments

Olive has been widely grown around the Mediterranean Basin for around 5000 years, where productivity and survival of this long-lived evergreen tree in environments of low and variable rainfall depend on physiological characteristics but also on management. The tree exercises effective control of water loss by transpiration and can also withstand intense internal water deficit that in turn increases extraction of water from soil. Critical aspects of management that maintain, albeit limited, transpiration and metabolic activity during hot dry summer months, are directed at both crop and understorey. Strategic decisions are selection of cultivar, tree density, and canopy size, together with surface management as tilled soil or as cover crop of selected species. Tactical adjustments are seen in extra pruning of olives and timing of tillage, or of grazing, mowing, or herbicides to restrict growth and water use of the understorey, especially following dry winters and during dry summers. Survival of olive orchards in low-rainfall climates requires that canopies intercept a small proportion of incident radiation, depending upon rainfall amount, distribution, and soil water storage capacity. Crop water balance models can assist in defining optimum canopy size for productivity and survival. New olive production in the Mediterranean and now extending widely in the ‘New World’, including in Australia, deviates widely from traditional practice. Orchards are planted at higher density, are generally irrigated, and trees are formed to suit mechanical pruning and harvesting. The environmental adaptation and understanding of water relations of olive in traditional systems are of limited applicability to these new production systems. Rather, there are now new emphases on nutrition, irrigation, canopy management, assimilate relationships, and fruiting performance to add to the existing questions of the suitability of cultivars to new environments in terms of productivity and oil quality.

Hydrogeologic processes in saline systems: playas, sabkhas, and saline lakes

Pans, playas, sabkhas, salinas, saline lakes, and salt flats are hydrologically similar, varying only in their boundary conditions. Thus, in evaluating geochemical processes in these systems, a generic water and solute mass-balance approach can be utilized. A conceptual model of a coastal sabkha near the Arabian Gulf is used as an example to illustrate the various water and solute fluxes. Analysis of this model suggests that upward flux of ground water from underlying formations could be a major source of solutes in the sabkha, but contribute only a small volume of the water. Local rainfall is the main source of water in the modeled sabkha system with a surprisingly large recharge-to-rainfall ratio of more than 50%. The contribution of seawater to the solute budget depends on the ratio of the width of the supratidal zone to the total width and is generally confined to a narrow zone near the shoreline of a typical coastal sabkha. Because of a short residence time of water, steady-state flow is expected within a short time (<100 years), while steady state for solutes may take much longer (>50,000 years). The solute composition of the brine in a closed saline system depends largely on the original composition of the input water. The high total ion content in the brine limits the efficiency of water–rock interaction and absorption. Because most natural systems are hydrologically open, the chemistry of the brines and the associated evaporite deposits may be significantly different than that predicted for hydrologically closed systems. Seasonal changes in temperature of the unsaturated zone cause precipitation of minerals in saline systems undergoing evaporation. Thus, during the hot dry season months, minerals exhibit retrograde solubility so that gypsum, anhydrite and calcite precipitate. Evaporation near the surface is also a major process that causes mineral precipitation in the upper portion of the unsaturated zone (e.g. halite and carnallite), provided that the relative humidity of the atmosphere is less than the activity of water. The slope of the fresh/brine-water interface in saline lake systems is shallower than in fresh/seawater interface because of the greater density difference between the fresh/brine-water bodies. The interface between sabkha brines and seawater slopes seaward, unlike normal marine–fresh water systems that slope landward. Moreover, the brine/seawater interface does not achieve steady state because it is pushed toward the sea by the sabkha's brine.