Category Archives: Drought Stress

Evaluation of the effectiveness of irrigation methods and fertilization strategies for alfalfa: A meta‐analysis

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Abstract

Alfalfa (Medicago sativa L.) plays an important role in livestock production in most regions of the world, but the quantity and quality of alfalfa have been critically affected by drought events in recent years. Thus, quantifying the efficacy of widely used strategies, irrigation methods and fertilization that are aimed at improving drought resistance in alfalfa is a worthy topic that has been addressed in a variety of ways using both field observations and simulation models. Although such strategies play a critical role in climate change adaptation, the global patterns of these strategies in a changing world remain elusive due to regional differences, such as drought features, strategy design and environmental conditions. Thus, by using effect size and statistical analyses, we synthesized three variables, namely, alfalfa yield, water use efficiency (WUE) and crude protein (CP), to examine the efficacy of irrigation methods and fertilization in drought areas based on peer-reviewed papers from 1990 to 2022. Our results showed that increasing drought stress reduces the alfalfa yield (−34.4%) but can increase the WUE (+13.7%). Both yield and WUE showed a negative relationship with the water deficit, but this phenomenon can be improved by using appropriate irrigation. The yield losses of alfalfa can be offset by implementing a fertilization strategy (+22%) under drought stress, especially for phosphate fertilizer. Overall, our results provide some evidence for the climate change adaptation of alfalfa under drought stress and indicate that fertilization is a more effective adaptation to improve alfalfa drought resistance (both yield and WUE, and yield and CP) than the irrigation method, which shows better performance in improving alfalfa WUE. Our synthesis of the effectiveness of irrigation methods and fertilization on alfalfa drought resistance can be used to develop scientific strategies for climate change adaptation for alfalfa and agriculture under climate change.

Tree lines do not reduce grassland productivity and herbage quality in alley cropping under drought

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Abstract

In alley cropping, woody perennials are combined with agricultural crops or grassland in order to benefit from favourable interactions between trees and crops. Trees influence growth and senescence processes in grassland as well as plant chemical composition and plant water use. In a field experiment with grassland and alley-cropped willow coppices, we analysed the impact of distance and position relative to the tree line on grassland herbage biomass, proportion of dead herbage and herbage quality in two successive growth periods of two experimental years. The experimental years were chosen so that growth periods among years showed a similar rainfall pattern. Relative ET (evapotranspiration) as defined by actual divided by potential evapotranspiration reflected the severity of water shortage with a moderately dry (relative ET ~ 0.5) first growth period with increasing dryness in the second growth period of each year. We determined bulk stomatal conductivity of the grass shoot by measuring δ13C (carbon) signatures. Stomatal conductivities were higher close to the trees in drier periods (i.e. more negative δ13C values). Herbage biomass decreased with decreasing relative ET, but showed no systematic influence of the tree line. We found that vegetation composition changed with distance to the tree line. The proportion of dead herbage was equal at all distances from the tree line under very dry conditions, but smaller close to the trees under moderately dry conditions. Herbage quality, as approximated by crude protein and ADF concentrations in live biomass, was higher closer to the tree line. We conclude that the tree line does not adversely affect grassland productivity under drought and improves the plant water status as reflected by the δ13C signature.

Silicon alleviates drought damage by increasing antioxidant and photosynthetic performance in cowpea

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Abstract

Water deficits have been considered the most restrictive environmental constraint on agricultural production worldwide. The current study aimed to investigate the role of silicon nutrition (Si) in activating defence mechanisms against drought damage in cowpea cultivars. The experiments were carried out in a randomized block design in a 2 × 2 × 4 factorial scheme, corresponding to two cowpea cultivars (BRS Novaera and BRS Tumucumaque), two water regimes (control well-irrigated and water deficit) and four Si levels (0, 1.0, 2.0 and 4.0 mM). Plant growth and physiological and biochemical indicators were evaluated 28 days after drought imposition. Drought significantly reduced the photosynthetic pigments (Chl b and Chl total), gas exchanges (net photosynthesis, transpiration and stomatal conductance) and, consequently, all growth parameters of cowpea plants compared with well-irrigated plants. However, Si at 2.0 mM activated critical responses in the BRS Novaera cultivar under drought, almost recovering plant performance and increasing drought tolerance. The beneficial Si-induced effects were closely related to increased accumulation of Si, carbohydrates and free amino acids that likely promoted osmoregulation and were associated with an improved antioxidant system composed of proline and the activity of SOD, CAT and APX. These metabolic alterations were sufficient to enable enhanced net photosynthesis and plant growth. In conclusion, Si counteracts the deleterious effects of water deficit by efficiently inducing antioxidant defence and photosynthetic performance in Novaera plants. Si nutrition may constitute a potential strategy to cultivate cowpea plants in water-scarce areas from arid and semiarid regions.