Water Management of Czech Crop Production in 1961–2019

This study aims to evaluate the water balance of the crop mix of the Czech Republic and the tendencies of its development during the period 1961–2019. For calculating water deficits, methodology from ČSN 750434 (Czech technical standards) was used and on its basis, the deficits of the ten most frequently represented crops of the Czech Republic were calculated. These results were then put into the context of the development of precipitation totals and the development of average annual temperatures in the observed period. Furthermore, statistical tools were used for the identification of relationships between the observed variables and the tested hypotheses to verify the statistical significance of the observed changes. The results show that the overall irrigation deficit nearly doubled in Czech agriculture when comparing the averages for the periods 1961–1970 and 2010–2019. This change was evaluated as statistically significant. Furthermore, there were also statistically significant increases in water deficits in the cases of wheat, barley, rye, oats, legumes, and rapeseed. The sowing areas of the observed crops recorded statistically significant change in all cases. Only in the case of wheat, maize and rapeseed were there increases in sowing area, specifically 146%, 642.4%, and 1132.7%, respectively. For other crops, a decrease in sowing areas was observed. This finding points to decreasing commodity diversity in Czech agriculture, which, in combination with a high degree of intensification and selected agrotechnical practices, contributes to a lower retention capacity for the soil and landscape to retain water, which in turn influences the overall water balance of the Czech agrarian sector.

Correlation approach in predictor selection for groundwater level forecasting in areas threatened by water deficits

Reliable long-term groundwater level (GWL) prediction is essential to assess the availability of resources and the risk to drinking water supply in changing climatic and socio-economic conditions, especially in areas with water deficits. The modern approach in this area involves the use of machine learning methods. However, the greatest challenge in these methods lies in the optimization of input selection. The presented research concerns the selection of the best combination of predictors using the Hellwig method. It served as a preprocessing technique before GWL prediction using support vector regression (SVR) and multilayer perceptron (MLP) for three wells in the Greater Poland Province, where the largest water deficits occur, in the period 1975–2014. The results of this method were compared with those of the regression method, general regression model. For the case study under investigation, the Hellwig method found GWL at lags of −1 and −2 months, all precipitation from the current month, and delayed by −1 to −6 months, and past temperature at months −1, −3, −4 and −6 as the most informative input set. Such input led to a model accuracy of 0.003–0.022 for a mean squared error and r2 of >0.8. The results obtained with SVR were slightly better than those with MLP. Moreover, every well required an individual set of predictors, and additional meteorological inputs improved the models’ performance.

Potato (Solanum tuberosum L.) Growth in Response to Foliar Silicon Application

As silicon induces abiotic stress tolerance in crop plants, it was hypothesized that foliar silicon application could improve potato growth in an early crop culture. The effect of dosage (0.25 dm3∙ha–1 or 0.50 dm3∙ha–1) and time (the leaf development stage, BBCH 14–16, tuber initiation stage, BBCH 40–41, or both the leaf development stage and tuber initiation stage) of application of the silicon-based biostimulant Optysil (200 g SiO2 and 24 g Fe in 1 dm3) on potato growth was investigated. Optysil caused an increase in plant height and above-ground plant biomass, enlarged leaf area and decreased leaf weight ratio (LWR), and, as a result, increased tuber number and tuber weight per plant. The effect of Optysil depended on a water deficit during potato growth. The average tuber weight per plant in the cultivation treated with Optysil was higher by 23% under periodic water deficits during potato growth, and by 13% under drought conditions, than in the cultivation without the biostimulant. Dosage of Optysil had a significant effect on above-ground plant biomass and leaf area in the warm and arid growing season. Under drought stress, Optysil at 0.50 dm3∙ha–1 stimulated potato growth more than at 0.25 dm3∙ha–1. Under periodic water deficits during potato growth, the time of Optysil application affected potato growth more than the biostimulant dosage. The plants produced greater above-ground biomass and had a larger leaf area with two Optysil applications; one in the initial plant growth period (BBCH 14–16), and a repeated treatment in the tuber initiation stage (BBCH 40–41). The tuber weight per plant was positively correlated with the plant height, above-ground plant biomass, leaf area, and LWR.

Vermicompost Leachate, Seaweed Extract and Smoke-Water Alleviate Drought Stress in Cowpea By Influencing Phytochemicals, Compatible Solutes and Photosynthetic Pigments

Drought is a major constraint for agricultural production worldwide and is likely to become aggravated by global warming. It can induce land degradation, exorbitant food prices and menace livelihoods. Approaches for retaining optimal yield, especially in rainfed staple crops such as cowpea (Vigna unguiculata) are paramount. Biostimulants; vermicompost leachate (VCL), seaweed extract [Kelpak® (KEL)] and smoke-water (SW) have exhibited effective amelioration for plants under abiotic stresses, however, research on cowpea remains scarce. Therefore, this study aimed to investigate the effects of seed priming of cowpea with VCL, KEL and SW on the growth, photosynthesis and biochemical levels in cowpea cultivated under three watering regimes. SW treatment amplified growth variables (i.e., foliage, shoot height, root length and number of flowers) of water-stressed cowpeas. KEL- and VCL-treated seeds significantly augmented shoot and nodules production by 2 and 4-fold respectively, compared to the control. Leaf carbohydrates and photosynthetic pigments in KEL- and SW-treated plants increased considerably under severe water deficits, while leaf proteins decreased by more than 3-fold. The biostimulants also lowered phenolic and flavonoid concentrations. Increasing and decreasing levels of soluble sugars, proteins, photosynthetic pigments, phenolics and flavonoids indicate stress alleviation and osmotic adjustment to water deficits. These biostimulants are a suitable alternative to improve soil fertility, growth, and yield of staple crops under water stress conditions.

Annual yield and botanical composition of four dryland grass species with or without nitrogen over six years

Nitrogen (N) and water availability affect pasture production and persistence. Yield and botanical composition of four monocultures of brome (BR), cocksfoot (CF), perennial ryegrass (RG) and tall fescue (TF) were evaluated with (+N) or without (-N) N at Ashley Dene farm, Canterbury, over six growth seasons from establishment in 2014/15 (Year 1) to 2019/20 (Year 6). Total annual yields ranged from 2.04 (RG-N; Year 1) to 12.7 t DM/ha/yr (CF+N; Year 3). Yields differed among species in Years 1, 3, 4 and 6 when TF pastures had the lowest production. There was no difference in DM production from BR, CF and RG pastures. Additionally, +N pastures produced ~55% more yield than –N pastures in Years 3 and 5 when spring/summer rainfall was adequate to maintain growth. Sown grasses accounted for >89% of total DM yield in Years 1 and 2 but the proportion of total annual DM production from sown species declined from Year 3. By Year 6, sown species accounted for 48±3.3 (TF) to 64±3.3% (BR, CF and RG) of total annual DM production. Generally, TF failed to perform in this dryland environment. In contrast, the production and persistence of the other three species were not different when subjected to water deficits alone.

Pasture resilience reflects differences in root and shoot responses to defoliation, and water and nitrogen deficits

The yield of a pasture is directly proportional to the amount of light plants intercept and allocate to different organs. When plants are carbon (C) limited, due to defoliation, they allocate more C preferentially to shoots to restore leaf area. In contrast, water and nitrogen (N) limitations lead to a greater allocation of C to roots. Changes in the root:shoot ratio therefore reflect changes in C and N partitioning and indicate their relative priority. A major factor that influences plant responses to stress is their ability to store and remobilise reserves to restore leaf area. Species with tap roots, like lucerne, have a large potential C and N storage capacity that is utilised seasonally for storage and remobilisation. This has been used to develop seasonally based grazing management rules. Similarly, recommendations to graze perennial ryegrass at the 2- or 3-leaf stage are based on the balance between maximizing growth rates and the need to replenish water-soluble carbohydrate reserves. However, perennial ryegrass has lower levels of perennial reserves than other grass species. This reduces its resilience to concurrent water deficits or N deficiency. Under these conditions maintaining the recommended 3-leaf grazing intervals and/or leaving higher post-grazing pasture masses are recommended to assist canopy recovery. Other grass species, such as cocksfoot and tall fescue, provide more resilience, particularly in response to water deficits.

Effect of water deficits on the growth and secondary metabolites of Salvia dolomitica Codd. and Salvia namaensis Schinz

Background: Salvia dolomitica Codd. and Salvia namaensis Schinz. are indigenous to southern Africa and are used as medicinal plants in folk medicine.Aim: This study aimed to assess the effects of different levels of water deficit treatments on the growth, concentration of secondary metabolites, and anti-Fusarium oxysporum activity of S. dolomitica and S. namaensis.Setting: Experiments were carried out on the Bellville campus of the Cape Peninsula University of Technology, Cape Town.Methods: Four weeks old seedlings of the two species were subjected to 3-, 6-, 9- and 12-day water deficit regimes. Secondary metabolites such as polyphenols, alkaloids, and flavanols were assessed using spectroscopic methods. The anti-fungal activities of crude extracts obtained from plants were evaluated in a micro-dilution bioassay.Results: In all treatments, the plant height, crown width, number of stems and leaves, and fresh and dry weights reduced with increased water deficits. Acetone extracts from all treatments showed anti-fungal activity. However, extracts from the treatment with moderate water deficit (6-day watering interval) recorded significantly (P 0.01) better inhibition of F. oxysporum at the 18 h post incubation than the commercial fungicide, Mancozeb.Conclusion: This research has revealed that mild to moderate water deficit level favours the accumulation of alkaloids in S. dolomitica. Meanwhile, mild to severe water deficit significantly lowered flavanol content in S. namaensis. There was a correlation between the increase in total alkaloid contents and the enhanced anti-fungal activity of extracts of S. dolomitica. The present findings pave the way for optimised cultivation of medicinal plants and development of bioactive natural products.

An Agro-Pastoral Phenological Water Balance Framework for Monitoring and Predicting Growing Season Water Deficits and Drought Stress

Sharing simple ideas across a broad community of practitioners helps them to work together more effectively. For this reason, drought early warning systems spend a considerable effort on describing how hazards are detected and defined. Well-articulated definitions of drought provide a shared basis for collaboration, response planning, and impact mitigation. One very useful measure of agricultural drought stress has been the “Water Requirement Satisfaction Index” (WRSI). In this study, we develop a new, simpler metric of water requirement satisfaction, the Phenological Water Balance (PWB). We describe this metric, compare it to WRSI and yield statistics in a food-insecure region (east Africa), and show how it can be easily combined with analog-based rainfall forecasts to produce end-of-season estimates of growing season water deficits. In dry areas, the simpler PWB metric is very similar to the WRSI. In these regions, we show that the coupling between rainfall deficits and increased reference evapotranspiration amplifies the impacts of droughts. In wet areas, on the other hand, our new metric provides useful information about water excess—seasons that are so wet that they may not be conducive to good agricultural outcomes. Finally, we present a PWB-based forecast example, demonstrating how this framework can be easily used to translate assumptions about seasonal rainfall outcomes into predictions of growing season water deficits. Effective humanitarian relief efforts rely on early projections of these deficits to design and deploy appropriate targeted responses. At present, it is difficult to combine gridded satellite-gauge precipitation forecasts with climate forecasts. Our new metric helps overcome this obstacle. Future extensions could use the water requirement framework to contextualize other water supply indicators, like actual evapotranspiration values derived from satellite observations or hydrologic models.

Maize Male Reproductive Organs Affected by Different Timings of Water Deficit

Compared with female reproductive organs, the development of male reproductive organs was got less attention in maize because of its oversupply in amount even under water deficit. Thus, a rainout shelter experiment was designed to explore the effect of different timings of water deficit on pollen vitality and exterior and interior ultra-structure of pollen grains, starch particles in pollen grains, anther fresh weight, and vascular bundle number and its organizational structure in tassel pedicel. There were five water treatments included in this study, viz. well water treatment (CK), water deficit during 6- to 8- leaf stage (V6 − 8), 9- to 12- leaf stage (V9 − 12), 13-leaf stage to tasseling (V13 − T), and silking to blister (R1 − 2), respectively. Results showed that the percentage of pollen grains with strong vitality decreased remarkably by 27.3–45.9% under water deficits, while that of pollen grains with weak vitality increased by 27.2–34.7%. The percentage of pollen grains with no vitality was significantly increased only when water deficit occurred around silking, which was up to 8.6% for V13 − T and 19.7% for R1 − 2 compared with 1.0% for that of CK. Both shrunken pollen apertures (including annulus and operculum) and less starch particles might partially explain the weakened pollen vitality for water deficits before tasseling. Furthermore, the assimilation flux to male reproductive organs might be restricted by the influenced vascular bundle system under water deficits before tasseling, with manifestation showing in anther fresh weight and starch particle status in pollen grains. Specifically, V9 − 12 and V13 − T water deficits delayed differentiation of vascular bundle but had no influence on vascular bundle number, which might be one reason for their decreased anther fresh weight and less starch particles in pollen grains. Conversely, V6 − 8 water deficit significantly decreased vascular bundle number but had no significant influence on anther fresh weight and starch particles in pollen grains. R1 − 2 water deficit almost had no influences on above indicators except for pollen vitality. Overall, this research highlight that male reproductive organs could be influenced by water deficits in maize, which deserves more attention in further breeding especially under the background of high-quality requirement for pollen vitality of the maize hybrids that have a small tassel size.

Physiological and root morphological responses in different combinations of rootstock-scion of cacao to water deficit

Grafting is a common practice in cacao cultivation, but it has not been reported whether rootstock-scion combinations respond differently in terms of water transport, growth, or nutrient uptake under varying soil water availability conditions. The effects of water deficits on water potential (Ψf), basal diameter (db), root growth, chlorophyll and leaf concentrations of nitrogen (N) were evaluated in 16 rootstock-scion combinations that resulted from four rootstocks and four scion clones. Grafted seedlings were subjected to two water regimes: 21 days without irrigation (WD) and continuous irrigation (I). Under WD conditions, Ψf tended to be lower when using the EETP800 clone with the four rootstocks, indicating that this clone may have a higher rate of transpiration. The greater Ψf (p <0.05) obtained with the EET400 and EET399 rootstocks-scion combinations indicate higher water uptake capacity by the root systems of these rootstocks, which permits the maintenance of adequate transpiration rates and higher Ψf. The higher db, chlorophyll content and leaf N content obtained in the combinations of scions with the EET400 rootstock under WD impart on this rootstock a more favorable degree of adaptability for tolerating water deficits. However, this tolerance is not associated with increased root growth, which indicates that higher efficiency of water uptake is related to metabolic and physiological processes rather than a larger root surface.