Late-season Drought Research Articles

Responses of plant leaf economic and hydraulic traits mediate the effects of early- and late-season drought on grassland productivity.

Drought can occur at different times during the grassland growing season, likely having contrasting effects on forage production when happening early or later in the season. However, knowledge about the interacting effects of the timing of drought and the development stage of the vegetation during the growing season is still scarce, thus limiting our ability to accurately predict forage quantity losses. To investigate plant community responses to drought seasonality (early- vs. late-season), we established a drought experiment in two permanent grasslands of the Swiss Jura Mountains that are used for forage production. We measured three plant functional traits, including two leaf traits related to plant economics (specific leaf area, SLA; leaf dry matter content, LDMC) and one hydraulic trait related to physiological function (predicted percentage loss of hydraulic conductance, PLCp), of the most abundant species, and plant above-ground biomass production. Plant species composition was also determined to calculate community-weighted mean (CWM) traits. First, we observed that CWM trait values strongly varied during the growing season. Second, we found that late-season drought had stronger effects on CWM trait values than early-season drought and that the plant hydraulic trait was the most variable functional trait. Using a structural equation model, we also showed that reduction in soil moisture had no direct impacts on above-ground biomass production. Instead, we observed that the drought-induced decrease in above-ground biomass production was mediated by a higher CWM PLCp (i.e. higher risk of hydraulic failure) and lower CWM SLA under drought. Change in CWM SLA in response to drought was the best predictor of community above-ground biomass production. Our findings reveal the importance of drought timing together with the plant trait responses to assess drought impacts on grassland biomass production and suggest that incorporating these factors into mechanistic models could considerably improve predictions of climate change impacts.

Structural memory in grapevines: Early season water availability affects late season drought stress severity

Abstract In the future drought events are expected to occur more frequently, with unpredictable rain and heat events. In current research we investigated how different water availability patterns influenced late season plant water status in Vitis vinifera. ‘Cabernet Sauvignon’ grapevines were grown for three consecutive years. We compared the response to five water availability regimes: High, Intermediate, Low (along all season) and High-to-Low (High during the beginning of vegetative seasons switched to low during the rest of season) and Low-to-High (opposite treatment). Midday stem water potential (SWP) was measured weekly to determine the seasonal pattern of drought stress. Xylem anatomy was investigated by trunk vessel diameter measurements, and specific axial xylem conductivity was calculated according to Hagen-Poiseuille's law. Vines exposed to high water availability treatment showed improved seasonal water status along the season, compared to vines in the low treatment. Vines exposed to High-to-Low water regime showed a markedly improved water status at the beginning of the season, but became the most severely stressed toward the end of season. The SWP values were more negative in the High-to-Low regime even when compared to the Low water regime. Water availability at the beginning of the season (during main period of cambial activity) determined the vessel characteristics: high water availability during cambial activity increased vessel diameter and thus specific hydraulic conductivity. Our data strongly indicates that regulated drought stress can be induced by manipulating xylem structural parameters via controlling water availability during the period of stem cambial activity.

Sowing date effects on dry matter remobilization and yield of triticale (Triticosecale wittmack) under late season drought stress

A 2-year field experiment using a randomized complete block design with the treatments arranged as split-split-plot with three replicates was conducted to investigate the effects of different sowing dates. Different irrigation regimes and different triticale cultivars were tested during 2014 and 2015 growing seasons. Under cutting off irrigation at the milk development stage, Sanabad with 46.2% had higher relative water content on December 3 sowing date. Assimilate remobilization in cutting off irrigation at dough development was more than that at milk development and Sanabad had the highest assimilate remobilization on 3 December sowing date in both years. In both years, Sanabad had the highest remobilization efficiency. The highest contribution of pre-anthesis assimilates to grain was obtained on 3 December sowing date in both years in Sanabad. Lower grain yield in Juanillo cultivar under cutting off irrigation, appeared to be due to reduction in remobilization efficiency, especially by cutting off irrigation at milk development stage in late sowing date. Overall, Sanabad was more tolerant to cutting off irrigation than Juanillo.

Drought-induced decline of productivity in the dominant grassland species Lolium perenne L. depends on soil type and prevailing climatic conditions

Severe constraints on grasslands productivity, ecosystem functions, goods and services are expected to result from projected warming and drought scenarios under climate change. Negative effects on vegetation can be mediated via soil fertility and water holding capacity, though specific mechanisms are fairly complex to generalise. In field drought experiments, it can be difficult to disentangle a drought effect per se from potential confounding effects related to vegetation or soil type, both varying along with climate. Furthermore, there is the need to distinguish the long-term responses of vegetation and soil to gradual climate shift from responses to extreme and stochastic climatic events. Here we address these limitations by means of a factorial experiment using a single dominant grassland species (the perennial ryegrass Lolium perenne L.) grown as a phytometer on two soils types with contrasted physicochemical characteristics, placed at two elevation sites along a climatic gradient, and exposed to early or late-season drought during the plant growing season.Warmer site conditions and reduced precipitation along the elevational gradient affected biogeochemistry and plant productivity more than the drought treatments alone, despite the similar magnitude in volumetric soil moisture reduction. Soil type, as defined here by its organic matter content (SOM), modulated the drought response in relation to local site climatic conditions and, through changes in microbial biomass and activity, determined the seasonal above and belowground productivity of L. perenne. More specifically, our combined uni- and multivariate analyses demonstrate that microbes in a loamy soil with low SOM are strongly responsive to change in climate, as indicated by a simultaneous increase in their C,N,P pools at high elevation with cooler temperatures and wetter soils. Contrastingly, microbes in a clay-loam soil with high SOM are mainly sensitive to temperature, as indicated by a strong increase in microbial biomass under warmer temperatures at low elevation and a concomitant increase in C:N, C:P and N:P ratios. High SOM promoted a better annual yield of the phytometer grass under warmer climate and the effect of drought on productivity was transient. In contrast, low SOM reduced cumulative yield under warmer conditions and root production strongly decreased, enduring a lasting drought effect. Microbes in soils with high organic matter remained more active during warmer and drier conditions, ensuring soil fertility and stimulating a higher overall plant nutrient availability and productivity.Our study highlights the important role of soil type for grassland responses to both stochastic climatic extremes and long-term climate change. Management practices enhancing SOM accumulation via organic residue incorporation seem a promising way to mitigate the effects of increased temperature and drought on plants and soil microbes alike promoting thereby a sustainable ecosystem functioning.

Sustaining the beneficial effects of maize production in Nigeria: Does adoption of short season maize varieties matter?

AbstractIn order to ensure sustainability of maize production in short-season environments of Nigeria, the Sudan savanna taskforce of Kano–Katsina–Maradi (KKM) Pilot Learning Site promoted short-season maize varieties in 2008 via Innovation Platforms (IPs). In the light of the promoted varieties, we evaluated the adoption and net benefits (productivity and income) of the maize varieties. We used cross-sectional household data elicited from 600 sampled households, double-hurdle model and propensity score matching. There was a remarkable increase in the adoption of short-season maize varieties in 2014 compared to what was obtained in a baseline conducted in 2008. Our empirical findings revealed that the adoption of the short-season maize varieties promoted through the IPs had significant productivity and income increasing effects. This implies that policy interventions to ensure sustainable maize intensification in the face of environmental limitations, such as early and late season drought, should intensify the promotion of short-season varieties in Sudan savannas. This will require well-concerted agricultural extension that can leverage IPs in view of its potentials.

Monsoon variability trends and strategies to get through its vagaries in rice-based systems in eastern India.

Abstract The trend of increasing monsoon variability in eastern India has led to increased risk of growing crops during the monsoon period. The rainfall pattern has become more erratic due to the shrinking of monsoon period 60-70 days from the normal 120 days, leading to drought and unusual frequent torrential rainfall exceeding 200-250 mm/day, causing floods during the past few decades. The duration and magnitude of drought and the number of dry spells also have increased. These stresses not only affect the yield of rice but also reduce the area and production of succeeding crops, resulting in low system productivity. Rice is the major crop in monsoon season in eastern India. Hence, technological or management options to cope with monsoon variability are discussed based on the available literature and results from the experiments conducted in eastern India, particularly in Odisha. Direct seeded rice (DSR) is an apt option for delayed onset of the monsoon that enables better use of early rains. In this regard, DSR helps reduce the risk of-of late-season drought by avoiding the stress period. Thus, DSR allows farmers to undertake early sowing of the subsequent crops, leading to higher system productivity. The performance of short-duration drought- and flood-tolerant rice varieties in stress-prone areas are reviewed and discussed here. Rice nursery enterprise in private- as well as community-sector has been proved as an effective strategy to ensure timely availability of healthy seedlings. However, the scale of these technologies/management options in eastern India is facing a tough challenge due to weed infestation, lack of availability of tolerant anaerobic and stagnant flood varieties, and appropriate machinery, in addition to socio-economic constraints to access the technologies.

Adoption of Drought Tolerant Maize Varieties under Rainfall Stress in Malawi

AbstractWe examine adoption of drought tolerant (DT) maize varieties using a four‐round panel dataset from six districts in Malawi. There is an increase in adoption of DT maize from 3% in 2006 to 43% in 2015 in our data. We focus on the effect of past drought exposure on adoption and the likelihood of DT maize being distributed under the Farm Input Subsidy Programme (FISP). Results show that past exposure to drought increases the probability of DT maize seed being distributed through FISP. Farmers who accessed maize seed subsidy coupons and were previously exposed to late season dry spells are more likely to use the seed subsidy coupon to redeem DT maize seed. The likelihood of adoption and adoption intensity (area under DT maize) are positively influenced by previous early season dry spells and access to seed subsidy. Previous late season droughts also positively affect adoption intensity. On the other hand, area share under DT maize is positively correlated with early season dry spells and past exposure to late season dry spells but negatively related to seed subsidy. FISP in Malawi appears to have stimulated adoption of DT maize directly through subsidy and indirectly through generating farmers’ experiences of the performance of DT varieties under drought conditions.

Co-limitation by nitrogen and water constrains allocation response to drought in deciduous and evergreen shrubs in a semi-arid ecosystem

Semi-arid regions worldwide are expected to experience reduced precipitation with future climate change, in addition to increased intensity of precipitation events, heightening the pulsed nature of water availability in these systems. Shifting biomass allocation is a plastic response of species to altered resource availability, and optimal allocation theory predicts plants should increase allocation to roots when water is limiting to growth. However, optimal allocation could be influenced by other factors, such as plant nutrient status and the seasonality of precipitation. Here, we evaluated the allocation response of eight common shrub species (four deciduous, four evergreen) from the Mediterranean climate region of Southern California to experimental manipulation of nitrogen and water availability, as well as seasonal drought. Evergreen species increased allocation to roots in response to low water availability to a greater degree than deciduous species, and also showed less of a decline in total biomass with water limitation, consistent with the predictions of optimal allocation theory. Deciduous species were more limited by nitrogen than evergreen species, requiring them to maintain high allocation below-ground regardless of water availability. Evergreen species were also able to equalize root allocation in response to early- versus late-season drought, while deciduous species responded non-optimally, reducing allocation to roots when early-season soil moisture was plentiful, resulting in the most strongly reduced growth by late-season drought. These experiments demonstrate how optimal allocation theory can be used to predict species responses to environmental changes in semi-arid systems, but should account for patterns of co-limitation and seasonality of resources.

Direct and Indirect Costs of Frost in the Australian Wheatbelt

Breeding for improved reproductive frost tolerance could allow greater yield and economic benefits to be achieved by (i) reducing direct frost damage and (ii) allowing earlier sowing to reduce risks of late-season drought and/or heat stresses. We integrated APSIM-Wheat simulations with economic modelling to evaluate economic benefits of virtual genotypes with different levels of frost tolerance for the Australian wheatbelt.Results highlighted substantial potential national economic benefits, with estimated industry profit increasing by (i) more than 55% for virtual genotypes with improved frost tolerance in silico, by (ii) 115% when sowing date was optimised for virtual frost-tolerant genotypes, and by (iii) an extra 35% (i.e. 150% in total) when using optimal nitrogen application. The total benefit potential was estimated at AUD 1890 million per annum if all these improvements could be combined. Regional benefits varied. In the West, the main benefits arose from improved frost tolerance reducing losses due to direct frost damage and applying additional nitrogen. In the East, earlier sowing allowed by tolerant genotypes resulted in large economic benefit. Overall, the analysis suggests significant economic benefits to the Australian wheat industry, should a source of frost tolerance be found.

Effect of drought stress on qualitative characteristics of canola cultivars in winter cultivation

To determine the appropriate canola cultivars for winter cultivation under late-season drought stress conditions, a factorial split-plot test was conducted in a complete randomized blocks design with three replications for two cultivation years (2014–2016) in Karaj, Iran. In this work, cultivations at two levels included fall cultivation (Oct. 7) and winter cultivation (Feb. 4). The irrigation was conducted at three levels including routine irrigation (control), irrigation interruptions from flowering and pod formation stage in factorial status in main plots and five Brassica napus L. cultivars including Sarigol, Delgan, Jacomo, Jerumeh and Hyola 401 in subplots. The interaction effect of cultivation date × irrigation × cultivar on the features of palmitic acid, linolenic acid, linoleic acid, oleic acid, erucic acid, glucosinolate and oil yield was significant at the level of 1%. The results indicated that Delgan cultivar with the highest oil yield (1582 kg/ha) in the winter cultivation date and normal irrigation conditions as well as with standard levels of erucic acid and glucosinolate can be effective in canola cultivation in the new stage of winter cultivation. Moreover, in winter cultivation and in the late-season drought stress conditions, hybrids Hyola 401 with the highest seed yield, and standard oligosaccharide and glucosinolate can also be recommended in late-season drought stress conditions.

Climate and synchrony with conspecifics determine the effects of flowering phenology on reproductive success in Silene acaulis

ABSTRACT Changes in flowering phenology resulting from climate change could impact individual plant fitness and population viability. Flowering phenology can mediate plant reproductive success in several ways, including pollinator interactions, flowering synchrony with conspecifics, and timing of suitable abiotic conditions. We explored factors that control phenology and reproductive success for an alpine cushion plant, Silene acaulis, across two years and four sites, totaling 1,123 plants, in Colorado, USA. We investigated relationships between flowering time, flowering synchrony, and reproductive success with local abiotic conditions and pollinator behavior. Mean flowering phenology was strongly correlated with the timing of snowmelt across sites and years. Relative to mean flowering times, earlier flowering plants generally produced more flowers and experienced greater soil moisture during flowering but reduced synchrony with conspecifics. Fruit set tended to increase with greater soil moisture, synchrony during flowering, and earlier flowering times. Pollinator visitation increased with local Silene flower density. Earlier snowmelt and drier conditions later in the season favor earlier flowering, but these effects are partially counteracted by the positive effects of synchrony, perhaps because of changes in pollinator visitation. Overall, while both biotic and abiotic effects influence reproductive success, late-season drought may outweigh the benefits of flowering synchrony to increasingly favor earlier flowering.

Response of Canola Advanced Lines to Delay Plantings upon Late Season Drought Stress

In order to evaluation of canola advanced lines response to delay plantings under late season drought stress conditions, an experiment was carried out in a factorial split-plot arrangement based on RCBD with three replications during two years (2012-2014) in Karaj of Iran. Treatments were; (1): Planting date in two levels (16 October and 1 November), (2): irrigation, in two levels (I1: normal irrigation as control and I2: restricted irrigation after pod formation stage) as main plots and (3): twelve oilseed rape genotypes as sub plots such as BAL2, BAL1, BAL3, BAL6, BAL8, BAL9, BAL11, BAL15, L72, R15, L109 and Okapi. The interaction effects of planting date, irrigation and genotype on pod number per plant, seed number per pod, 1000-seed weight, seed yield, and oil yield were significant at 1% level probability. The maximum seed yield under planting at the appropriate time (16 October), normal irrigation and drought stress conditions (restricted irrigation after pod formation stage) was observed in Okapi and L109, respectively). Among genotypes, R15 line under delay planting (1 November) and both normal irrigation and drought stress conditions (restricted irrigation after pod formation stage) showed the maximum seed yield.

Evaluation of Yield and Yield Component of Spring Barely Genotypes under Late Season Drought Stress

Evaluation of Yield and Yield Component of Spring Barely Genotypes under Late Season Drought Stress

Evaluation of Late Season Drought in Barley Genotypes using some Drought Tolerance Indices

Evaluation of Late Season Drought in Barley Genotypes using some Drought Tolerance Indices

Intercropping Induces Changes in Specific Secondary Metabolite Concentration in Ethiopian Kale (Brassica carinata) and African Nightshade (Solanum scabrum) under Controlled Conditions.

Intercropping is widespread in small-holder farming systems in tropical regions and is also practiced in the cultivation of indigenous vegetables, to alleviate the multiple burdens of malnutrition. Due to interspecific competition and/or complementation between intercrops, intercropping may lead to changes in plants accumulation of minerals and secondary metabolites and hence, alter nutritional quality for consumers. Intercropping aims to intensify land productivity, while ensuring that nutritional quality is not compromised. This study aimed to investigate changes in minerals and secondary plant metabolites in intercropped Brassica carinata and Solanum scabrum, two important African indigenous vegetables, and evaluated the suitability of this combination for dryer areas. B. carinata and S. scabrum were grown for 6 weeks under controlled conditions in a greenhouse trial. Large rootboxes (8000 cm3 volume) were specifically designed for this experiment. Each rootbox was planted with two plants, either of the same plant species (mono) or one of each plant species (mixed). A quartz sand/soil substrate was used and fertilized adequately for optimal plant growth. During the last 4 weeks of the experiment, the plants were either supplied with optimal (65% WHC) or low (30% WHC) irrigation, to test the effect of a late-season drought. Intercropping increased total glucosinolate content in B. carinata, while maintaining biomass production and the contents of other health related minerals in both B. carinata and S. scabrum. Moreover, low irrigation led to an increase in carotene accumulation in both mono and intercropped S. scabrum, but not in B. carinata, while the majority of kaempferol glycosides and hydroxycinnamic acid derivatives of both species were decreased by intercropping and drought treatment. This study indicates that some health-related phytochemicals can be modified by intercropping or late-season drought, but field validation of these results is necessary before definite recommendation can be made to stakeholders.

Economic assessment of wheat breeding options for potential improved levels of post head-emergence frost tolerance

Frost, during reproductive developmental stages, especially post head emergence frost (PHEF), can result in catastrophic yield loss for wheat producers. Breeding for improved PHEF tolerance may allow greater yield to be achieved, by (i) reducing direct frost damage and (ii) facilitating earlier crop sowing to reduce the risk of late-season drought and/or heat stress. This paper provides an economic feasibility analysis of breeding options for PHEF tolerant wheat varieties. It compares the economic benefit to growers with the cost of a wheat breeding program aimed at developing PHEF tolerant varieties. The APSIM wheat model, with a frost-impact and a phenology gene-based module, was employed to simulate direct and indirect yield benefits for various levels of improved frost tolerance. The economic model considers optimal profit, based on sowing date and nitrogen use, rather than achieving maximum yield. The total estimated fixed cost of breeding program was AUD 1293 million, including large scale seed production to meet seed demand, with AUD 1.2 million year−1 to run breeding program after advanced development and large scale field experiments. The results reveal that PHEF tolerant varieties would lead to a significant increase in economic benefits through reduction in direct damage and an increase in yield through early sowing. The economic benefits to growers of up to AUD 4841 million could be realised from growing PHEF tolerant lines if useful genetic variation can be found. Sensitivity analyses indicated that the benefits are particularly sensitive to increases in fixed costs, seed replacement, discount rate, and to delays in variety release. However, the investment still remains viable for most tested scenarios. Based on comparative economic benefits, if breeders were able to develop PHEF tolerant varieties that could withstand cold temperatures −4°C below the current damage threshold, there is very little further economic value of breeding total frost tolerant varieties.

Genotypic Regulation of Aflatoxin Accumulation but Not Aspergillus Fungal Growth upon Post-Harvest Infection of Peanut (Arachis hypogaea L.) Seeds.

Aflatoxin contamination is a major economic and food safety concern for the peanut industry that largely could be mitigated by genetic resistance. To screen peanut for aflatoxin resistance, ten genotypes were infected with a green fluorescent protein (GFP)—expressing Aspergillus flavus strain. Percentages of fungal infected area and fungal GFP signal intensity were documented by visual ratings every 8 h for 72 h after inoculation. Significant genotypic differences in fungal growth rates were documented by repeated measures and area under the disease progress curve (AUDPC) analyses. SICIA (Seed Infection Coverage and Intensity Analyzer), an image processing software, was developed to digitize fungal GFP signals. Data from SICIA image analysis confirmed visual rating results validating its utility for quantifying fungal growth. Among the tested peanut genotypes, NC 3033 and GT-C20 supported the lowest and highest fungal growth on the surface of peanut seeds, respectively. Although differential fungal growth was observed on the surface of peanut seeds, total fungal growth in the seeds was not significantly different across genotypes based on a fluorometric GFP assay. Significant differences in aflatoxin B levels were detected across peanut genotypes. ICG 1471 had the lowest aflatoxin level whereas Florida-07 had the highest. Two-year aflatoxin tests under simulated late-season drought also showed that ICG 1471 had reduced aflatoxin production under pre-harvest field conditions. These results suggest that all peanut genotypes support A. flavus fungal growth yet differentially influence aflatoxin production.

Effects of Altered Seasonality of Precipitation on Grass Production and Grasshopper Performance in a Northern Mixed Prairie.

Climatic changes are leading to differing patterns and timing of precipitation in grassland ecosystems, with the seasonal timing of precipitation affecting plant biomass and plant composition. No previous studies have examined how drought seasonality affects grasshopper performance and the impact of herbivory on vegetation. We modified seasonal patterns of precipitation and grasshopper density in a manipulative experiment to examine if seasonality of drought combined with herbivory affected plant biomass, nitrogen content, and grasshopper performance. Grass biomass was affected by both precipitation and grasshopper density treatments, while nitrogen content of grass was higher with early-season drought. Proportional survival was negatively affected by initial density, while survival was higher with early drought than with full-season drought. Drought timing affected the outcome, with early summer drought increasing grass nitrogen content and grasshopper survival, while season-long and late-season drought did not. The results support arguments that our knowledge of plant responses to seasonal short-term variation in climate is limited and illustrate the importance of experiments manipulating precipitation phenology. The results confirm that understanding the season of drought is critical for predicting grasshopper population dynamics, as extreme early summer drought may be required to strongly affect Melanoplus sanguinipes (F.) performance.

Yield comparison of simulated rainfed wheat and barley across Middle-East

Rain-fed wheat and barley are key crops in the Middle-East. A slight improvement in the effective use of water and in grain yield could greatly improve lives of subsistence farmers. This study aimed to evaluate the relative merits of wheat and barley in this region by simulating yields across 404 uniformly spread locations across 30 growing seasons. The results emphasized the primary importance of sowing date in each location. In comparison to wheat, barley generally was capable of rapid progress through its development stages allowing it to avoid deleterious late-season droughts and to have greater yields in low rainfall regions. A large part of Middle-East appeared unsuited for rain-fed production of these two grain species if seasonal yield variability is a concern.

Effect of Zeolites and Zinc on the Physiological Characteristics of Canola under Late-Season Drought Stress

ABSTRACTResearch was performed during the 2010 and 2011 growing seasons to investigate the effect of zeolites and zinc foliar application on the physiological characteristics of canola cultivars at different moisture regimes. A factorial split-plot experiment was performed on the basis of the randomized complete block design with three replications in the Seed and Plant Improvement Institute, Karaj, Iran. The treatments were as follows: (1) irrigation (I), complete (I1), and restricted (I2) at the pod formation stage, (2) zeolite (Z), 0 (Z1), and 15 t ha−1 (Z2), and (3) (Zn), zinc sulfate concentrations of 0%, 0.1%, and 0.2% (Zn1, Zn2, and Zn3) at the pod formation stage. These treatments were applied on Licord, RGS003, and Opera cultivars. Although applying Z and Zn had positive effects on the quality of canola, the highest performance and the best results were obtained using a combination of Z and Zn. The combined application of Z and Zn increased the relative water content, yield, and oil yield and decreased the stomatal resistance and canopy temperature. Therefore, with the low cost of natural Z and moderate Zn intake, these treatments can be used to enhance the performance of canola, especially in regions frequently subjected to water stress.