Normal Rainfall Conditions Research Articles

The potential to reduce runoff generation through improving cropping and tillage practices in a sub-humid continental climate

Agricultural sustainability is threatened by both water deficit and water excess, especially at the presence of extreme meteorological events resulting from climate change. However, there has been lack of demonstrations on management options with long-term values for agricultural adaptation to runoff. Using 20 years of monitoring data (1993‒2012) for two experimental fields in the Canadian Prairies as a case study, we quantified the effects of rainfall characteristics, crop type and biomass, and tillage on growing-season runoff generation using regression analyses and thereafter scenario comparisons. With growing-season gross rainfall ranging between 183 and 456 mm, runoff responses varied between 0 and 59 mm. Over the 20-year study period, 70%‒74% of the growing-season runoff was generated by rainfall events > 100 mm. Compared to high-intensity tillage, long-term conservation tillage reduced both overall runoff and runoff in large events likely by improving water infiltration. Under both tillage methods, growing-season runoff significantly increased with increasing rainfall but decreased with increasing biomass (R2 range: 0.40‒0.58; p range: 0.0007‒0.02). At the event level, the rainfall-runoff relationship followed a piecewise regression model (Cd = 0.82; p < 0.0001; “breakpoint” rainfall event = 105 mm), in which runoff increased slowly before reaching the “breakpoint” but rose sharply afterwards. Due to a greater biomass, canola resulted in less runoff than wheat. Scenario analyses showed that increasing crop biomass by 50% under the current average rainfall conditions could reduce runoff by 81‒86% in wheat and 100% in canola. The reduction may be attributed to the combined effects of crop on interception, evapotranspiration, and infiltration. In conclusion, although in a sub-humid continental climate like the Canadian Prairies there are generally low amounts of rainfall runoff, this study demonstrates significant runoff in some years, especially following large rainfall events. Runoff generation can be significantly reduced through improving cropping and tillage practices, and such effects on regional water retention should be further assessed by considering the past and future changes in climate and management.

Analysis of Land Water Balance in Various Rainfall Conditions and Its Utilization to Determine Planting Patterns of Food Crops in the Eastern Part of Seram District of Seram Island

Soil water balance calculation is one of the methods used to estimate the dynamics of soil water content during plant growth. This study aims to describe rainfall conditions and analyze soil water balance as well as determine the growing season and composition of food crop combination patterns based on the available growing season in East Seram Island. This research uses rainfall data for 30 years of observation period 1992-2021 from Geser Meteorological Station (Data analysis with the following stages: (i) rainfall analysis (ii) calculation of average rainfall (iii) determination of rainfall with a 75% chance (iv) calculation of soil water balance using the Thornthwaite and Mather method (v) determination of the growing season and cropping pattern. The results showed that the average rainfall in East Seram was 2,194 mm/year with a water deficit (D) occurring in October and November, then the rainfall had a 75% chance of being exceeded at 1,439 mm/year with a water deficit of 228 mm/year which lasted for eight months, namely August - March. The growing season under normal rainfall conditions was available throughout the year, while under high rainfall conditions, a 75% chance of the growing season was available for five months, namely May and October. The cropping patterns and crop combinations used were monoculture, polyculture, and intercropping with combinations of cassava, maize, sweet potato, groundnut, mung bean, cassava-corn, cassava-peanuts/green beans, maize-peanuts, cassava-corn-peanuts/green beans, cassava-corn-horticultural crops.

Investigating the effects of landscape productivity on the spatial ecology of a threatened marsupial inside feral predator exclosures

AbstractLandscape productivity and resource dispersion are key drivers of the movement patterns of many species. In less productive environments, home ranges are generally larger as individuals travel further to access resources. The greater bilby (Macrotis lagotis) has been reintroduced to several feral predator exclosures to reduce their extinction risk. Understanding how landscape productivity and resource dispersion influence bilby space use is critical to enable effective management of populations in exclosures. At two exclosures, we tested three hypotheses: 1. Bilbies would preferentially utilize habitats with sandy substrates (&lt;20% clay content), as they are suitable for digging burrows and foraging pits; 2. Home ranges would be larger at the arid site compared to the semi‐arid site due to lower productivity and patchier distribution of preferred habitats; and 3. Bilbies would travel further each night at the arid site to access preferred habitats. Rainfall was used as an indicator of productivity, and dispersion of preferred habitats as an indicator of resource dispersion. The study was undertaken during average rainfall conditions and under similar bilby population densities at both sites. GPS loggers recorded home ranges and movements of 10 bilbies at the arid site, and 11 bilbies at the semi‐arid site. Seventeen of the 21 bilbies preferentially utilized habitats with sandy substrates, which were less abundant at the arid site. There were no significant differences in home range size or nightly movements between the sites for either sex. We suggest the average rainfall conditions at both sites, and the dietary flexibility of bilbies, supported the maintenance of relatively small and stable home ranges (particularly for females). The effects of landscape productivity and resource dispersion on bilby space use are more likely to be evident during extended periods of below average rainfall. Bilby home range studies during low rainfall conditions (e.g. drought) are required for the effective, long‐term management of exclosure populations.

DEVELOPMENT OF SUSTAINABLE TOURISM INSTRUMENTS FOR ECOLOGICAL RESILIENCE IN PARI ISLAND, DKI JAKARTA

&lt;p&gt;&lt;span&gt;The research objective is to develop an instrument for assessing sustainable tourism in the context of ecological resilience in Pari Island, DKI Jakarta. This study uses research and development methods through the ADDIE model approach. The research sample includes potential and factual coral reef areas for tourism in Pari Island. The results of the study concluded that the validation of important instruments includes: (1) natural/biological criteria, namely unique and beautiful coral reefs, quite unique tidal phenomena, endemic flora and fauna such as seagrass and fish habitat, as well as other aquatic biota, ease of observing aquatic biota, opportunities for trekking, snorkeling, etc. as well as the support of comfortable temperature and humidity, normal rainfall conditions, as well as well-managed household industrial waste; and (2) Physical environmental criteria such as dominant beaches, controlled coastal land conversion rate and protected from pollution, ease of utilizing rocky beaches for friendly productive activities. The environment, such as maintaining fish, marine tourism, and others as well as the existence of a map of the distribution of coral reefs that accurately depicts local potential as well as information related to the low risk of natural disasters (landslides, floods, tsunamis). &lt;/span&gt;&lt;/p&gt;

Co-evolution among soil thickness, epikarst weathering degree, and runoff characteristics on a subtropical karst hillslope

Carbonate landscapes make up one-fifth of the terrestrial land area, a better understanding of the coupling relationship between the soil–epikarst form and hydrological function is imperative for hydrology and landscape evolution modeling. In this study, we monitored a total of 158 rainfall-runoff events on a karst slope between 2019/4 and 2022/5 in southwest China, while simultaneously examining the soil–epikarst architecture (924 pairs of soil thickness and epikarst weathering degree). The results indicated that soil thickness increased with the underlying epikarst weathering degree, and soil thickness was positively correlated with epikarst thickness (P<0.001). Additionally, a significant positive relationship (P<0.001) was observed between surface runoff (SR) and soil thickness, as well as a significant negative relationship (P=0.0018) between subsurface runoff (SSR) and soil thickness. These findings imply the dominance of SR and SSR (under normal rainfall conditions) in runoff plots with deep soil layers and thin soil layers, respectively. The soil thickness threshold at which the hillslope discharge shifted from being SSR-dominated to SR-dominated was approximately 50 cm. Nonetheless, a positive relationship was found between SR and SSR under extreme rainfall events, indicating the establishment of hydrological connectivity between the surface and subsurface. Moreover, the hillslope discharge when the rainfall depth is lower than 50 mm is primarily composed of either SR or SSR from different plots. In other words, the hillslope discharge is typically influenced by both SR and SSR when the rainfall depth exceeds 50 mm. We finally proposed a positive feedback loop among soil thickness, epikarst weathering degree, and the hydrological function of the soil–epikarst system (water storage and release). These findings enhance our understanding of the complex interactive relationships in hillslope hydrology by illuminating the physical links between critical zone structures and hydrological processes on the karst slope.

Development and Evaluation of Irrigation Management Strategies for Higher Yield and Water Productivity of Wheat: A Simulation Modelling Approach

: In the present study, CERES-wheat model was calibrated and validated for predicting growth and yield of wheat by using three years of experimental data (2016-17, 2017-18 and 2019-20) under different irrigation treatments. Further the model was run with twenty years of weather data (2000-01 to 2019-20) with optimum management practices under different irrigation scenarios for developing the irrigation management strategies for obtaining higher grain yield and irrigation water productivity (IWP) under dry, wet and normal rainfall conditions. The results indicated that the model slightly overestimated the maximum leaf area index (LAI) and consequently the grain yield in water stress condition; however, overall, model could excellently simulate anthesis and maturity with RMSE&lt;4 days, RMSEn&lt;10% and d&gt;0.90, as well as grain yield (RMSE= 163-204 kg/ha, RMSEn =3-6%, d = 0.93-0.98) for three, four and five irrigations from CRI to jointing, CRI to anthesis and CRI to dough stage, respectively. The IWP was increased with the decrease in number of irrigations. The maximum yield was obtained when the four irrigations applied from CRI to Anthesis under all-weather years (Dry, wet and normal), but it was as par with the three irrigations applied at CRI, Tillering and Jointing or CRI, Tillering and Anthesis stage for wet years. Under three irrigations scenario the maximum yield of 5050-5302 kg/ha and irrigation water productivity (IWP) of 33.7-35.3 kg/ha-mm was noticed when three irrigations applied at CRI, Tillering and Jointing followed by at CRI, Tillering, Anthesis stage and CRI, Jointing and Anthesis stage and under wet year no difference was noticed in yield and IWP whether three irrigations were applied at CRI, Tillering and Jointing or CRI, Tillering and Anthesis stage and under two irrigations scenario, the maximum grain yield as well as IWP was obtained when applied at CRI and Tillering followed by CRI and Jointing stage.

CLIMATE CHANGE AND PLANT TIME (STUDIES IN RICE CULTIVATION STRATEGY PEASANT, CASE STUDY: LEUWIHIDEUNG VILLAGE DARMARAJA SUB DISTRICT, SUMEDANG)

The main livelihood of people living in rural areas with the main crop is rice peasant. Rice cultivation by the peasant is rely availability of water, both from irrigation or rain water. Peasant are planting rice irrigation sourced from both technical and semi-technical irrigation especially in the dry season flow of the river by making a ”Dawuan". However, the availability of river water also depends on the climate or rainfall and upstream environmental conditions that concerned. The purpose of this paper is to describe the impact of climate change on cropping time and or income of rice peasant in the village Leuwihideung. The selection of these villages or peasant because this village is partly technical and partly irrigated half is rained and or there are peasant who grow crops in both the land. The data obtained from the results of field research using a qualitative approach. Peasant in the village Leuwihideung on normal rainfall conditions in semi-technical fields could grow rice three times a year by relying on irrigation, while the rained land can be planted once a year rely on rain water. However, recent rainfall is erratic even on irrigated land impact on cropping time that can only be planted with rice twice a year and the impact on rained cropping time. Climate change is not only an impact on the incomes of peasant but also have an impact on peasant’ income.

Application of Agent-Based Modeling in Agricultural Productivity in Rural Area of Bahir Dar, Ethiopia

Effective weather forecast information helps smallholder farmers improve their adaptation to climate uncertainties and crop productivity. The main objective of this study was to assess the impact of weather forecast adoption on crop productivity. We coupled agent-based and crop productivity models to study the impact of farmers’ management decisions on maize productivity under different rainfall scenarios in Ethiopia. A household survey was conducted with 100 households from 5 villages and was used to validate the crop model. The agent-based model (ABM) analyzed the farmers’ behaviors in crop management under different dry, wet, and normal rainfall conditions. ABM results and crop data from the survey were then used as input data sources for the crop model. Our results show that farming decisions based on weather forecast information improved yield productivity from 17% to 30% under dry and wet seasons, respectively. The impact of adoption rates due to farmers’ intervillage interactions, connections, radio, agriculture extension services, and forecast accuracy brought additional crop yields into the Kebele compared to non-forecast users. Our findings help local policy makers to understand the impact of the forecast information. Results of this study can be used to develop agricultural programs where rainfed agriculture is common.

Drainage Technologies for Enhancing Productivity of Temporary Waterlogged Vertisols

A field study on Broad Bed and Furrows (BBF) to control surface waterlogging and mole drain to control temporary sub-surface water logging in Vertisols regions of Madhya Pradesh in soybean-wheat cropping system was conducted for a period of four years from 2016 to 2019. The BBF system comprising of 65 m length, 1.50 m spacing, and different depths (150 - 250 mm) resulted in 29-35% and 14-15% increase in soybean crop yield over control in normal and above normal rainfall (rainfall &gt; 1050 mm) and below normal rainfall condition (rainfall &lt; 750 mm), respectively. Mole drainage (MD) comprising of mole drains of 85 mm size formed at 4 m drain spacing and at a depth of 500 mm with 65 m lateral length resulted in 51% increase in soybean grain yield over the control under normal and above normal rainfall conditions. Soybean grain yield increased by 66- 74% under the treatment comprising of BBF coupled with MD over the control in above normal rainfall condition. The grain yield increase under mole drainage coupled with BBF for below normal rainfall condition was non-significant over the treatments comprising of BBFs only. The benefit-cost ratio for soybean crop cultivation using BBF, MD, BBF coupled with MD and conventional systems were found to be 1.65, 1.99, 2.03, and 0.98, respectively. The payback period of mole drainage technology was found to be less than 2 years. The effect of mole drainage on subsequent wheat crop recorded 11-12% increase in yield over the control. Field study revealed that BBF and BBF coupled with MD systems are technically feasible and economically viable for effective drainage of Vertisols.

Outcomes of water deficit stress on the physiological quality of soybean seeds

Abstract: This study aimed to compare the physiological seed quality of soybean cultivars produced under or without water deficit stress. Seed samples of three soybean cultivars produced in the 2019/2020 crop season were collected in a rural property and in a company that obtains the cultivars. In the rural property, the seeds were produced under water deficit stress and high temperatures during the crop’s and were characterized by the presence of greenish seeds. In the company that obtains the cultivars, the sample consisted of a certified seed lot produced under normal rainfall and temperature conditions, without greenish seeds. Germination, average germination time, germination speed index, average germination speed, the number of normal and abnormal seedlings, the seedling height and dry weight, the root evaluations (length, surface area, volume, average diameter and dry mass) and the total seedling dry mass were also evaluated. Soybean seeds produced under water deficit stress showed a reduction in physiological quality directly proportional to the percentage of greenish seeds present in each seed lot. The occurrence of water deficit stress on the soybean in the reproductive and maturation stages negatively impacts the soybean crop installation in the subsequent season due to the low physiological seed quality.

Assessment of Meteorological Drought in Climate Variability Context within the Comoe River Transboundary Watershed

In the context of climate variability resulting in a decrease in rainfall with a severe drought, a spatio-temporal study of this phenomenon remains imperative for the efficient management of water resources. This paper aims to assess the long-term rainfall drought trend and breakpoints within the Comoe River watershed. From monthly rainfall data series (1960-2000), Standardized Precipitation Index (SPI) values were calculated for a time scale of 3 months (SPI.3). Statistical tests for breaks (CUSUM, and t-Student) and trends (Man-Kendall and Linear Regression) as well as the Sen’ slope method for estimating the magnitude of trends was applied. The breaks dates observed are mostly located after the 1970s. Based on SPI.3 values below the threshold of 0.84 chosen as an indicator of drought, rarely has more than half of the catchment area been affected by drought. The average watershed affected is about 20% over the study period (1960-2000). The most representative years, in terms of spatial expansion of the drought, in decreasing order of importance are: 1983, 1992, 1972 and 1982. The years 1982 and 1983 stand out for their exceptional condition, as the drought-affected 50% to 90% of the total catchment area. SPI.3 series from 1960 to the various break dates recorded slopes between -0.01 and 0.00 with a slight drought trend for most of the catchment. After the break periods, almost the entire northern part of the basin is characterized by slight moisture with Sen’s slopes between 0.000 and 0.005. The southern part will remain slightly subject to normal rainfall conditions.

A comparison of environmental impacts between rainwater harvesting and rain garden scenarios

Rain garden (RG) is a simple alternative to reduce pollutant loads carried through runoff. However, RG construction impacts the environment, where it demands evidence of net benefits generated once commissioned for operation. This study has simulated the reduction of runoff and pollutant loads due to the installation of RGs. Consequently, the reduction of the impacts on the environment was estimated using the LCA method. A comparison was carried out between the scenarios with and without RG with the most feasible (environmentally) rainwater harvesting (RWH) system. Three RG sizes are considered, such as 3, 4, and 6 m2 in dry, average, and wet annual rainfall conditions. The catchment-scale results showed that the runoff generation impacts of the RGs' operation phase were about (24–54%), (21–49%), (21–47%), and (14–45%) of the system without RG on eutrophication, human toxicity-carcinogenic, ecotoxicity-freshwater, and ecotoxicity-marine, respectively. However, once fabrication & installation were added, RG had much higher net impacts than without RG, except for eutrophication and ecotoxicity-freshwater. Hence, the net ecotoxicity-freshwater impact was lower for all scenarios except 4 and 6 m2 RG sizes during dry rainfall conditions. The most feasible RWH scenarios (e.g., 2000 & 3000 L tanks) had net impacts of 3–81% of the RG systems on global warming, human toxicity-carcinogenic, and ecotoxicity-terrestrial categories. On the other hand, RWH had net impacts of 105–200% on ozone depletion and eutrophication and 51–119% on the ecotoxicity-freshwater and ecotoxicity-marine of the RG systems.

Comparing the water use metrics of just-in-case, just-in-time and justified irrigation strategies using a scenario-based tool

Efficient water use is an important outcome of effective irrigation scheduling strategies. We developed a physically-based hydrology tool IrriSET (Irrigation Strategy Evaluation Tool) to simulate the performance of different scheduling strategies against three water use metrics - amount of irrigation used, drainage resulted from irrigation, and duration root zone soil water (crop soil water reservoir) was held within optimum pasture growth conditions during the irrigation season. IrriSET was tested on an irrigated dairy farm in Canterbury, New Zealand, simulating the daily soil water balance using observed and estimated data on rainfall, evaporation, root zone soil water holding capacity, irrigation supply reliability, irrigation infrastructure limitations (how quickly and how much irrigation could be applied per event), and irrigation application efficiency (designed versus actual application) from eighteen irrigation seasons for three scheduling strategies – ‘just-in-case', ‘just-in-time', and ‘justified’. Just-in-case, a rostered, supply-based irrigation strategy, resulted in the most irrigation applied per season and drainage generated, and the least duration of time soil water held in the optimum pasture growth condition. Soil water demand-based just-in-time, and demand- and weather-forecast based justified irrigation strategies resulted in similar water use metrics, though the latter consistently and marginally outperformed the former. Even during irrigation seasons with below normal rainfall and average irrigation supply conditions, though the demand and supply-based strategies used similar irrigation amounts, the latter held soil water in the optimal growth range longer than the former. A strategy that proactively manages irrigation based on supply (irrigation water availability and forecast rainfall) and demand (soil water condition) has been shown to be environmentally sustainable and positively influential of soil water availability within root zone, and thus productivity.

Rainfall-Linked Megafires as Innate Fire Regime Elements in Arid Australian Spinifex (Triodia spp.) Grasslands

Large, high-severity wildfires, or “megafires,” occur periodically in arid Australian spinifex (Triodia spp.) grasslands after high rainfall periods that trigger fuel accumulation. Proponents of the patch-burn mosaic (PBM) hypothesis suggest that these fires are unprecedented in the modern era and were formerly constrained by Aboriginal patch burning that kept landscape fuel levels low. This assumption deserves scrutiny, as evidence from fire-prone systems globally indicates that weather factors are the primary determinant behind megafire incidence, and that fuel management does not mitigate such fires during periods of climatic extreme. We reviewed explorer’s diaries, anthropologist’s reports, and remotely sensed data from the Australian Western Desert for evidence of large rainfall-linked fires during the pre-contact period when traditional Aboriginal patch burning was still being practiced. We used only observations that contained empiric estimates of fire sizes. Concurrently, we employed remote rainfall data and the Oceanic Niño Index to relate fire size to likely seasonal conditions at the time the observations were made. Numerous records were found of small fires during periods of average and below-average rainfall conditions, but no evidence of large-scale fires during these times. By contrast, there was strong evidence of large-scale wildfires during a high-rainfall period in the early 1870s, some of which are estimated to have burnt areas up to 700,000 ha. Our literature review also identified several Western Desert Aboriginal mythologies that refer to large-scale conflagrations. As oral traditions sometimes corroborate historic events, these myths may add further evidence that large fires are an inherent feature of spinifex grassland fire regimes. Overall, the results suggest that, contrary to predictions of the PBM hypothesis, traditional Aboriginal burning did not modulate spinifex fire size during periods of extreme-high arid zone rainfall. The mechanism behind this is that plant assemblages in seral spinifex vegetation comprise highly flammable non-spinifex tussock grasses that rapidly accumulate high fuel loads under favorable precipitation conditions. Our finding that fuel management does not prevent megafires under extreme conditions in arid Australia has parallels with the primacy of climatic factors as drivers of megafires in the forests of temperate Australia.

On inferring population trends of mobile waterbirds from aerial transect surveys in variable environments

Monitoring waterbird populations in Australia is challenging for reasons of counting logistics, and because population aggregation and dispersion can shift rapidly in response to large spatio-temporal variations in resource availability. The East Australian Waterbird survey has conducted annual, aerial, systematic counts of waterbirds over eastern Australia for almost 40 years. It was designed to monitor waterbird populations using design-based inference though for many species this form of inference appears inadequate in the face of these challenges. Here we develop a state-space model-based Bayesian approach that, in addition to explicitly incorporating process noise and observation uncertainty, uses random effects and rainfall-derived covariates to model the year-to-year variation in the proportion of the total (super) population that is present on surveyed wetlands, and available to be counted. We use this model-based approach to estimate the superpopulation size of 45 waterbird species annually, and model the rate of population increase as a function of antecedent rainfall. The results confirm the strong positive effect of antecedent rainfall on population growth rates for nearly all species, and illustrate that species respond to rainfall differently in terms of habitat use, which influences whether they are present on surveyed wetlands. For many species, the year-to-year variation in the estimated proportion of the population on surveyed wetlands is very high. The results have implications for making inferences on population trends from these data, with the ability to model the year-to-year sampling variation a key requirement before the rate of population increase can be estimated with any precision. This study illustrates how to progress this approach, and infers that under average rainfall conditions, the general trend is for estimated superpopulation rates of increase to be negative, though for only a few species is this occurring with strong belief.

Rangeland Biodiversity and Climate Variability: Supporting the Need for Flexible Grazing Management

Resting or grazing exclusion is an effective practice widely adopted to restore degraded, arid rangelands. To understand its effect on plant diversity, we studied Hill’s diversity indices during two growing seasons (2017–2019). The experiment consisted of a three-level factorial design with four plant communities subjected to different resting durations (one, two, and three years) compared to continuously grazed areas (control). The results showed that rainfall plays an important role in arid rangeland restoration. Under favorable conditions, one-year grazing exclusion considerably enhanced species richness and evenness diversity compared to longer resting durations under dry to average rainfall conditions. The decision to how long livestock grazing exclusion would last should not be decided upfront as it depends on the climatic and the site-specific conditions. The findings of this study will have vital management implications for development agencies. Knowing that short grazing exclusion with adequate rainfall amount and distribution could be enough and offers a cost-effective technical option to ensure the sustainable restoration of arid rangeland. This flexible grazing management would also be more acceptable by the pastoral communities. Longer resting periods could have detrimental effects on arid rangeland vegetation, in addition to adding more pressure on the remaining rangeland areas open to grazing.

Rainfall Anomalies Pattern in Northwestern Nigeria (NWN)

Constant investigation into rainfall anomaly pattern is very crucial as it enables the detection of any departure from normal rainfall condition. When such departure is persistent and statistically significant, it could indicate climate change. This study seeks to investigate anomaly pattern of rainfall in north western Nigeria with the view to determine any extreme departure from established normal rainfall behavior (mean). The study used thirty years (30) rainfall data from 1987 to 2016. The data was obtained from the archives of Nigerian Meteorological Agency (NIMET) for six selected synoptic stations from the region. Purposive sampling technique was adopted in selecting the six synoptic stations given consideration to stations with longer consistent rainfall records. The data was subjected to Standardized Anomalies also known as Standardized Precipitation Index (SPI) to obtain anomaly values. The values were used to plot time series for each station. They were also used to determine the dry or years with drought i.e. negative values and wet or moisture years i.e. positive values. The findings showed that throughout the thirty years period, normal conditions dominated the study area with few pockets of dry conditions. The study concludes that rainfall anomalies pattern in north western Nigeria over the thirty years period under investigation was not too far from normal rainfall conditions.

CO2 exchange, dry matter accumulation and growth response of sorghum (Sorghum bicolor L. Moench) to terminal drought as affected by potassium and blended‐NPSBZn fertilization

AbstractSorghum production is constrained by terminal drought stress in semi‐arid areas of north‐eastern Ethiopia. Data from field experiments conducted in the region for two consecutive years (2015 – 2016) were used to investigate the effect of potassium (K) and NPSBZn‐blended fertilizer (BF) inputs on the drought response of sorghum through analysis of gas exchange, dry matter accumulation and growth parameters. Leaf gas exchange properties varied strongly with K and BF application both under normal rainfall and drought conditions. Data taken at anthesis in drought‐exposed sorghum indicated reduction of net photosynthetic rate (AN) with BF supply. AN declined from 15.7 µmol CO2/m2/s in the control to 13.4 µmol CO2/m2/s with application of 164 kg/ha BF. However, higher total dry matter yield was recorded at maturity in response to blended fertilizer and K inputs. Increasing supply of NPSBZn‐blended fertilizer was associated with declining leaf K content, increasing intercellular CO2 concentration and water use efficiency (WUE) during anthesis. Significant variations in crop growth rates were also observed in response to K and BF inputs. At physiological maturity, net assimilation rate (NAR) increased with K and BF inputs both under drought and normal rainfall conditions. In general, K application modulated the response of sorghum to BF input under both normal rainfall and drought conditions. Therefore, grain sorghum could benefit from early supply of K and BF fertilizer in drought prone areas of Northeastern Ethiopia.

Interactions between drought and shade on the productivity of winter pea grown in a 25‐year‐old walnut‐based alley cropping system

AbstractIn the face of climate change, more frequent drought events are expected in the Mediterranean regions. Alley cropping is an agroforestry practice that represents a promising adaptation strategy to sustain yield productivity under drier conditions. However, the presence of trees limits the productivity of the intercrop by reducing light availability and by competing for soil water resources, which could potentially exacerbate the yield losses due to drought conditions. Furthermore, the effects of co‐occurring drought and shade stresses on annual crops are still poorly understood. To tackle this issue, we performed a rainfall manipulation experiment on winter pea (Pisum sativum L.) grown in full‐sun conditions (agricultural control) and under different levels of shade in a 25‐year walnut‐based alley cropping system located in southern France. We evaluated first the effect of trees on light and water availability, and we then studied the effects of early drought (135 mm excluded from April to the end of May) and light conditions on crop performances and yield components. At 3.5 m from the tree line, light availability was reduced on average by 19% at south and 35% at north of trees over the entire crop cycle and mostly after tree budburst. The impact of trees on soil water content in the crop root zone was weak thanks to the good complementarity of the respective root systems. Under normal rainfall conditions, tree shade decreased pea yield from −25% to −77% compared to full‐sun conditions. In case of spring drought, pea yield was decreased by −22% in full‐sun conditions. The negative effect of tree shade was reduced and decreased pea yield only by −1% to −47%. Under the most intense shade conditions, pea yield was even higher under drought than in normal rainfall conditions. The analysis of crop dynamics and yield components revealed that the vegetative development of pea ceased under drought to the benefit of biomass allocation towards the reproductive organs. Pea yield was less impacted by tree shade under spring drought because yield elaboration relied less on the success of pod set, sensitive to shade and, more on grain filling, improved in case of early drought event. This study supports the hypothesis that agroforestry systems may be more resilient in the case of early drought.

Evaluation of Commercial Wheat Cultivars for Canopy Architecture, Early Vigour, Weed Suppression, and Yield

Herbicide resistance in weeds restricts control options, thereby escalating economic loss and threatening agricultural sustainability in cereal production. Field evaluation of the crop performance, competitive traits, and consequent weed suppressive potential of 13 commercial winter wheat (Triticum aestivum L.) cultivars was performed in central NSW Australia with a focus on the evaluation and modelling of above-ground interactions. In 2015 and 2016, replicated field trials were established with genetically diverse commercial wheat genotypes under moderate to low rainfall conditions in Wagga Wagga (572 mm) and Condobolin (437 mm) New South Wales, respectively. The heritage cultivar Federation and a commercial cultivar of winter cereal rye (Secale cereale L.) were included as known weed-suppressive controls. Crop and weed growth, as well as early vigour, leaf area index, and photosynthetically active radiation, were monitored at various crop phenological stages including early growth, vegetative, flowering, grain fill, and harvest. Significant differences between wheat cultivar and location were observed for crop biomass, early vigour, leaf area index, weed number, weed biomass, canopy architecture, and yield in both 2015 and 2016. Differences in weed establishment were largely impacted first by rainfall and season and secondly by crop architecture (i.e., height, size, canopy) and phenology (i.e., growth stages). Early vigour and early canopy closure were instrumental in suppressing weed establishment and growth. Cultivar performance and competition with weeds were also clearly influenced by both environmental factors and genotype, as evidenced by differences in early cultivar performance, yield, and weed suppression by season and location. Specifically, Federation, Condo, and Janz wheat cultivars were superior performers in terms of weed suppression in both locations and years; however, Federation produced up to 55% lower yield than recently introduced cultivars. Partial least squares (PLS) regression was performed to develop a predictive linear model for weed competition in commercial wheat cultivars based on weed dry biomass as the response variable and selected aboveground crop canopy traits as predictors. In 2015, the model differed in accordance with crop growth stage, but the impact of predictors on weed biomass at both locations was not significant. In 2016, under local above average rainfall conditions, the model showed a significant negative correlation (p &lt; 0.001) of most predictors on weed biomass (r2 = 0.51 at Condobolin, r2 = 0.62 at Wagga Wagga), suggesting the most influential factors in reducing weed numbers and establishment as crop vigour, biomass, and height. Our results indicate the establishment of competitive wheat cultivars in the absence of post-emergent herbicides resulted in a two to five-fold increased weed suppression over less suppressive genotypes, without significant yield penalties. Therefore, cultivar choice constitutes a cost-effective and sustainable weed management tool, particularly when weed pressure is significant.