Non-irrigated Treatment Research Articles

Soil chemical characteristics, yield and technological quality of sugarcane under subsurface drip irrigation with treated sewage effluent

ABSTRACT Sugarcane cultivation requires sustainable strategies to meet water and nutritional needs. This study tested the hypothesis that irrigation with treated sewage effluent (TSE) can meet the water needs of sugarcane plants, improving their technological quality and yield. The objective of this study was to assess the effects of subsurface drip irrigation (SDI) with TSE or surface reservoir water (SRW) on soil chemical characteristics and technological quality and productivity. Thus, an SDI system was installed at soil depths of 0.20 and 0.40 m to apply SRW and TSE to sugarcane plants, composing four irrigation treatments (TSE0.2 m, TSE0.4 m, SRW0.2 m and SRW0.4 m) and a control (non-irrigated treatment). Analyses of soil chemical characteristics in different layers showed no negative effects for the use of SDI, which maintained favorable soil conditions for sugarcane plantations. The surface layer (0–0.2 m) irrigated with SRW or TSE showed higher accumulation of nutrients and organic matter. The results confirmed the hypothesis that irrigation with TSE or SRW improves the technological quality and yield of sugarcane; the treatment TSE0.2 m showed the best results regarding increases in sugar yield and alcohol production. However, continuous monitoring of soil salinity is necessary in wastewater-irrigated agricultural systems.

Impact of deficit irrigation and planting density on grain yield and water productivity of maize grown under temperate continental climatic conditions

Variable frequent drought periods in Vojvodina region (the southeastern part of the Pannonian Plain, Serbia), severely limit maize (Zea mays L.) production under rainfed conditions. A four-year field experiment was conducted to investigate the effects of sprinkler deficit irrigation and plant density on yield and water use efficiency of maize grown on silty clay loam soil under temperate continental climate. The experiment included fully irrigated crop (I1), three deficit irrigation treatments (I2, I3 and I4 corresponding to 80, 50 and 40 % of crop evapontranspiration, respectively) and non-irrigated treatment (I0), and three plant densities (LPD: 54,900 plants ha–1; MPD: 64,900 plants ha–1; HPD: 75,200 plants ha–1) in four replicates. The results showed that grain yield, CWP (crop water productivity) and IWP (irrigation water productivity) varied significantly with irrigation amounts, plant densities and seasons. The irrigation rates and plant density interact significantly. MPD and HPD differed significantly from LPD in almost all seasons. With increasing irrigation and plant density, yield and CWP showed an increasing trend. The relative values of IWP increased with the rise of plant density and decreased with the amount of irrigation. The highest four-year average yield (15.03 t ha–1) was obtained in the I1-HPD treatment, while the lowest (9.30 t ha–1) was obtained in the I0-HPD treatment. The highest average values of CWP and IWP were recorded at I3-HPD or/and I2-HPD. The lowest CWP and IWP values were determined for I4-HPD and I4-MPD, respectively. In the pedo-climatic conditions of Vojvodina and similar regions, we recommend growing maize under the I1-HPDtreatment to achieve high yields. Under the water shortage conditions, the application of I2-HPD treatment is a favorable strategy saving 37 % of irrigation water, while reducing maize grain yield by ∼10 %.

Identifying High‐Yielding and Drought‐Tolerant Wheat Cultivars Based on Ideotypic Traits and Yield Responses to Stress

ABSTRACTDrought is one of the most adverse factors affecting plant growth and productivity. Identifying elite genotypes and their ideotypic traits conferring high yield potential and drought tolerance is critical in selecting and breeding drought‐tolerant wheat cultivars. In this study, we conducted field experiments at the Xinxiang Agricultural Comprehensive Experimental station in the North China Plain from 2018 to 2020 and assessed 209 wheat cultivars released since the 1940s under irrigated and nonirrigated conditions. Then, we selected drought‐tolerant cultivars by classifying them into four groups based on yield response to drought stress and several drought indices. Finally, the key ideotypic traits associated with high yield potential and drought tolerance were identified. Results indicated that the grain yield of the 209 cultivars decreased on average by 10.4% and 9.4% under nonirrigated treatment in 2018–2019 and 2019–2020, respectively, relative to full irrigation. The high‐yielding cultivars under both irrigation treatments are characterised by a compact plant type, larger thousand‐grain weight, larger chlorophyll content, higher leaf photosynthesis, shorter plant height and stay‐green traits. The stomatal and nonstomatal limitations are strongly associated with genotype yield performance, elucidating a potential mechanism underlying drought tolerance. Drought tolerance and yield stability of wheat cultivars have been improved through breeding over the past 70 years. Our findings enhance understanding of drought tolerance and identify genotypes and traits beneficial for breeding high‐yielding and drought‐tolerant cultivars.

Finding balance: Tree-ring isotopes differentiate between acclimation and stress-induced imbalance in a long-term irrigation experiment.

Scots pine (Pinus sylvestris L.) is a common European tree species, and understanding its acclimation to the rapidly changing climate through physiological, biochemical or structural adjustments is vital for predicting future growth. We investigated along-term irrigation experiment at a naturally dry forest in Switzerland, comparing Scots pine trees that have been continuously irrigated for 17 years (irrigated) with those for which irrigation was interrupted after 10 years (stop) and non-irrigated trees (control), using tree growth, xylogenesis, wood anatomy, and carbon, oxygen and hydrogen stable isotope measurements in the water, sugars and cellulose of plant tissues. The dendrochronological analyses highlighted three distinct acclimation phases to the treatments: irrigated trees experienced (i) a significant growth increase in the first 4 years of treatment, (ii) high growth rates but with a declining trend in the following 8 years and finally (iii) a regression to pre-irrigation growth rates, suggesting the development of a new growth limitation (i.e. acclimation). The introduction of the stop treatment resulted in further growth reductions to below-control levels during the third phase. Irrigated trees showed longer growth periods and lower tree-ring δ13 C values, reflecting lower stomatal restrictions than control trees. Their strong tree-ring δ18 O and δ2 H (O-H) relationship reflected the hydrological signature similarly to the control. On the contrary, the stop trees had lower growth rates, conservative wood anatomical traits, and a weak O-H relationship, indicating a physiological imbalance. Tree vitality (identified by crown transparency) significantly modulated growth, wood anatomical traits and tree-ring δ13 C, with low-vitality trees of all treatments performing similarly regardless of water availability. We thus provide quantitative indicators for assessing physiological imbalance and tree acclimation after environmental stresses. We also show that tree vitality is crucial in shaping such responses. These findings are fundamental for the early assessment of ecosystem imbalances and decline under climate change.

Olive-tree physiological response to biotic and abiotic stress fruit yield, oil quality and tolerance to Anthracnose: Doctoral thesis abstract

The olive tree is highly tolerant to water deficit and in humid climate regions, such as Uruguay, the need to irrigation is questioned. However, Uruguay's climate is characterized by high interannual variability, resulting in periods of water deficit. In the event of a water deficit, plants trigger a series of defense mechanisms to maintain cellular homeostasis, including increased antioxidant enzyme activity and cuticle thickening to prevent transpiration. These responses are common during abiotic stress and biotic stress caused by pathogen infections. Anthracnose, caused by the Colletotrichum complex, is a major disease in olive trees, leading to reduced fruit yield and oil quality. Mild drought stress has been found to activate the basal defense response, enhancing plant tolerance to pathogen infections. Therefore, the hypothesis was that exposing olive plants to moderate water deficit during the lipogenesis stage would trigger the basal defense response, increasing fruit tolerance to biotic stress caused by Colletotrichum acutatum. The study also examined whether this response was sustained under moderate water deficit. Results showed that water deficit induced anatomical and biochemical changes in olive fruits, promoting anthracnose tolerance with reduced incidence and severity of C. acutatum infection both in vitro and in vivo. Fruit weight and pulp/pit ratio decreased in response to water deficit, while cuticle thickness and fruit polyphenol content increased. An induction of enzymes related to hydrogen peroxide scavenging were observed, in particular PER and CAT. This enzymatic activity was induced by the pathogen inoculation treatment and was higher in the non-irrigated treatment. Severe water deficit resulted in significant reductions in fruit weight and oil content, but the fruits exhibited enhanced tolerance to anthracnose infection.

Effect of Different ET-Based Irrigation Scheduling on Grain Yield and Water Use Efficiency of Drip Irrigated Maize

The development of irrigation schedules based on water balance implies a study of daily plant water requirements. A properly selected irrigation method is also of most importance. The objective of this study was to find out how surface drip irrigation (SDI) and shallow subsurface drip irrigation (SSDI), as well as different ET-based irrigation scheduling for maize (reference evapotranspiration (ETo), pan evaporation (Eo), and local climatic coefficients (lc)), affect grain yield, water use efficiency (WUE), and yield response factor (Ky) of maize. The field experiments were conducted in Vojvodina, a northern part of the Republic of Serbia, on the calcareous gleyic chernozem soil, using a complete block design in three replicates in 2019–2021. The water balance method was used for irrigation scheduling. The nonirrigated treatment was used as a control. The yield in irrigation conditions was statistically higher as compared with the nonirrigated control variant. Concerning the tested parameters, especially the maize yield, reference evapotranspiration (ETo) should be recommended as the most acceptable method for assessing maize evapotranspiration. Preference should be given to SSDI compared to SDI because the installation of laterals can be performed together with the sowing, which can ensure the uniform and timely emergence of plants. Based on the Ky coefficient of 0.71, it can be concluded that maize is moderately tolerant to water stress in Vojvodina’s temperate climate. The results can contribute to precise planning and efficient irrigation of maize in the region, implying high and stable yields.

Microbial biomarkers of tree water status for next-generation biomonitoring of forest ecosystems.

Next-generation biomonitoring proposes to combine machine-learning algorithms with environmental DNA data to automate the monitoring of the Earth's major ecosystems. In the present study, we searched for molecular biomarkers of tree water status to develop next-generation biomonitoring of forest ecosystems. Because phyllosphere microbial communities respond to both tree physiology and climate change, we investigated whether environmental DNA data from tree phyllosphere could be used as molecular biomarkers of tree water status in forest ecosystems. Using an amplicon sequencing approach, we analysed phyllosphere microbial communities of four tree species (Quercus ilex, Quercus robur, Pinus pinaster and Betula pendula) in a forest experiment composed of irrigated and non-irrigated plots. We used these microbial community data to train a machine-learning algorithm (Random Forest) to classify irrigated and non-irrigated trees. The Random Forest algorithm detected tree water status from phyllosphere microbial community composition with more than 90% accuracy for oak species, and more than 75% for pine and birch. Phyllosphere fungal communities were more informative than phyllosphere bacterial communities in all tree species. Seven fungal amplicon sequence variants were identified as candidates for the development of molecular biomarkers of water status in oak trees. Altogether, our results show that microbial community data from tree phyllosphere provides information on tree water status in forest ecosystems and could be included in next-generation biomonitoring programmes that would use in situ, real-time sequencing of environmental DNA to help monitor the health of European temperate forest ecosystems.

Simulating soil C dynamics under intensive agricultural systems and climate change scenarios in the Matopiba region, Brazil

The recent agricultural expansion in the Matopiba region, Brazil's new agricultural frontier, has raised questions about the risk of increasing soil organic carbon (SOC) loss as large areas of native vegetation (NV; i.e., Cerrado biome) have been replaced by large-scale mechanized agriculture. Although sustainable managements, such as integrated crop-livestock (ICL) systems, are considered strategic to counterbalance the SOC loss associated with land-use change (LUC) while keeping food production, little is known about their long-term effects on SOC stocks in the Matopiba region. To this end, we used the DayCent model to simulate the effects of converting the management commonly used in this region, i.e., soybean-cotton rotation under no-tillage (NT), into ICL systems with distinct levels of intensification (e.g., crop rotations: soybean-pasture and soybean-pasture-cotton; soil and crop management: grass irrigation, scarification/harrowing, and length of grass cultivation) on long term SOC dynamics. Additionally, data from two projected climate scenarios: SSP2-4.5 [greenhouse gases emissions (GHG) will not change markedly over time and global temperature will increase by 2.0 °C by 2060] and SSP5-8.5 (marked changes in GHG emissions are expected to occur resulting in an increase of 2.4 and 4.4 °C in global temperature in the middle and at the end of the century) were included in our simulations to evaluate climate change effects on SOC dynamics in this region. Based on a 50-yr-time frame simulation, we observed that SOC stocks under ICL systems were, on average, 23% and 47% higher than in the NV (36.9 Mg ha−1) and soybean-cotton rotation under NT (30.9 Mg ha−1), respectively. Growing grasses interlaid with crops was crucial to increase SOC stocks even when disruptive soil practices were followed. Although the irrigation of grass resulted in an early increase of SOC stocks and a higher pasture stoking rate, it did not increase SOC stocks in the long term compared to non-irrigated treatments. The SSP2-4.5 and SSP5-8.5 climate scenarios had little effects on SOC dynamics in the simulated ICL systems. However, additional SOC loss (∼0.065 Mg ha−1 yr−1) is predicted to occur if the current management is not improved. These findings can help guide management decisions for the Matopiba region, Brazil, to alleviate the anthropogenic pressure associated with agriculture development. More broadly, they confirm that crop-livestock integration in croplands is a successful strategy to regenerate SOC.

Effect of irrigation and fertiliser doses on sweet corn yield, water consumption and water utilization

The experiment was conducted within a framework of a two-factor long-term trial at the Research Institute for Fisheries, Aquaculture and Irrigation, in Szarvas, Hungary. This was a special field experiment, in which lysimeters have been installed in the middle of 32 m2 field plots. The main factor was the water supply with 4 levels: i1: non-irrigated control; i2: irrigated with one third of the optimal water supply; i3: irrigated with two thirds of the optimal water supply; i4: optimum irrigated plot, according to the requirement of sweet corn test plant. The amount of released irrigation water was 0, 54, 106 and 158 mm per year on average over 5 years. Within every water supply treatment there were 4 nutrient supply rates (N): N1, N2, N3, N4 = 100, 200, 300 and 400 kg ha−1 NPK fertiliser substance in ratio 2:1:1. The number of replications was 4, and the experiment was arranged in split-plot design. In the studied years, the amount of precipitation varied between 92 and 264 mm from sowing to harvesting.The effect of fertiliser was less in the non-irrigated treatments compared to that of the irrigated ones, and the yield was increased only up to 200 kg ha−1 NPK treatment level. The NPK dose of 300 kg ha−1 proved to be optimal in the irrigated treatments in which the utilization of fertilizer doses increased parallel to the improving water supply. In addition, the ratio of first class products (cobs longer than 20 cm) increased to a greater extent than the yield as a result of irrigation and fertilization. Water requirement of sweet corn proved to be between 400–450 mm resulting in an average yield of 20–24 t ha−1, of which 18–20 t ha−1 came from marketable cobs. The amount of evapotranspiration fluctuated between 270–440 mm during the five years, depending on the quantity of water supply, but it changed to a lesser extent than the amount of the yield. Increasing the fertilizer dose practically did not affect ET in non-irrigated plants, but increased it by 20–30 mm in irrigated ones. The change was not significant.The productivity of ET was only 30–45 kg ha−1 mm−1 in the non-irrigated treatment, while it was 50–55 kg ha−1 mm−1 in the irrigated treatments, with higher values at the higher fertiliser rates. The productivity of irrigation water exceeded far over the productivity of ET at adequate nutrient supply. The yield increase per 1 mm of irrigation water was on average 60 kg ha−1 mm−1, which was considerably higher than the productivity of ET of non-irrigated plants (39 kg ha−1 mm−1). There was a positive correlation between the yield and ET, and a negative correlation between the yield and specific water consumption. Irrigation and fertilization increased the average yield to a greater extent than evapotranspiration, so as the average yield increased, the ET per unit of yield decreased, i.e. the productivity of evapotranspirated water increased.

Influence of sustained deficit irrigation and foliar kaolin application on almond kernel composition

Deficit irrigation and kaolin foliar application are agronomic practices that have been demonstrated to improve productivity and physiological response in almond trees but there is no consistent information on the effects on the kernel composition. The objective of this study was to evaluate the effect of different Sustainable Deficit Irrigation (SDI) strategies and kaolin application on some physicochemical composition of the cv Ferragnès almond (Prunus dulcis (Mill.) D.A. Webb). A randomized block design with five treatments was developed: non-irrigation (NI), non-irrigation with foliar kaolin application (NI+K), full irrigation (FI), and two levels of SDI receiving 70% and 35% of evapotranspiration (SDI75 and SDI35). Pomological parameters, volatile profile and oil composition were analyzed. SDI effect on kernel weight was reduced against full irrigation (FI) but substantially improved in comparison with the rainfed treatments (NI and NI+K). Irrigation treatments showed a lower volatile compounds concentration in comparison with rainfed treatment. The fatty acid composition of the oil was significantly affected, with all the irrigated treatments having higher oleic acid contents than the rainfed treatments, and therefore an expected increased shelf life. Kaolin application had no positive effects on the non-irrigated trees, other than an apparent increase in the total volatiles, a tendency also observed in the NI. Moderate water stress levels (SDI35) improved the synthesis of tocopherols compared to NI, FI and SDI70, which could be related to the adaptation of the almond tree to drought. SDI35 is therefore regarded as a very interesting approach, with significant improvements in comparison with non-irrigated trees, and a clear saving on water against full irrigation without significant pomological and chemical alterations.

Can Drip Irrigation without Film Mulching Be Favorable for Potato Growth in Eastern China?

The main measures to improve potato cultivation in eastern China are film mulching and drip irrigation. However, the film can cause soil pollution and inhibit plant growth because of non-degradable polyethylene, which is the main component of the film. Whether drip irrigation without mulching can improve potato yield needs to be fully explored. Field experiments were conducted at the Special Potato Experimental Station, China Agricultural University, Rizhao City, Shandong Province, China, in 2019 and 2020 to investigate the effects of mulching and soil wetted percentage on soil water and temperature distribution, as well as potato growth. In 2019, three treatments with soil wetted percentage of 50% were set up: black plastic film mulching (BMP2), transparent plastic film mulching (TMP2), and no mulching (NMP2). In 2020, soil wetted percentage treatments were added to the existing mulching treatments: no mulching without irrigation (NMP0) and no mulching with soil wetted percentage of 25% (NMP1), 50% (NMP2), and 75% (NMP3); black plastic film mulching without irrigation (BMP0) and black plastic mulching with 50% soil wetted percentage (BMP2); and transparent plastic film mulching with no irrigation (TMP0) and transparent plastic film mulching with 50% soil wetted percentage (TMP2). The results indicated that mulching did not have a significant effect (p < 0.05) on soil temperature, potato growth, and yield. Irrigation reduced soil temperature by a range of 0.4 to 3.0 °C during the high air temperature season. Irrigation significantly increased potato plant height, stem thickness, and yield. The potato yield under the irrigation treatment could be 16.0–24.9% greater than that under the non-irrigation treatment. The highest irrigation water use efficiency (IWUE) was achieved at soil wetted percentage P1 and P2, which were beneficial for water saving. The NMP1 and NMP2 treatments had 83.4% and 81.0% significantly higher IWUE than NMP3 treatment. Considering environmental protection, resource conservation, and economic efficiency, drip irrigation without mulching under soil wetted percentage P2 was suitable for potato cultivation in eastern China.

Influence of non-irrigation and seasonality on wine colour, phenolic composition and sensory quality of a grapevine (<i>Vitis vinifera</i> cv. Callet) in a Mediterranean climate

Most vineyards in Mediterranean areas are cultivated using a training system and drip irrigation. However, the increasing risk of water deficit stress due to global warming will mean that viticulture need to adapt to a tougher water-saving policy. Thus, we investigated the effects of total suppression of irrigation on a grapevine (Vitis vinifera cv. Callet) and the phenolic composition and sensory quality of this native red variety wine from the Balearic Islands over three seasons. Significant yield reductions of up to 15.6 %, 17.2 % and 22.2 % were observed in non-irrigated (NI) plants in 2016, 2017 and 2018 respectively, compared to irrigated plants (I); however, wine quality parameters improved. In the years with the highest rainfall (715 mm in 2016 and 799 mm in 2017), NI favoured the enrichment of sugars, anthocyanins and phenolic compounds in the wine and enhanced the development of aromatic components. However, with lower rainfall (524 mm in 2018), the NI treatment appeared to diminish the quality of the wine, particularly affecting the global sensory quality of the wines. Thus, development of specific water strategies tailored to the vineyard, year, vintage and grape variety may regulate the phenolic composition of red wines to meet production goals and reduce total water consumption.

Volatile sulfur compound in Pinot noir wines affected by vineyard irrigation, tillage, and nitrogen supplementation

The effects of vineyard nitrogen fertilization, tilling, and irrigation on the contents of volatile sulfur compounds in Pinot noir wines were investigated in this study. Wines were made from two field blocks of twelve combinations of irrigation (dry or irrigated), tillage (tilled or not tilled), and fertilization (none, foliar nitrogen supplementation or soil applied nitrogen) from three vintages of Vitis vinifera cv. Pinot noir. The concentrations of volatile sulfur compounds were quantified using solid-phase micro-extraction and gas chromatography/ pulse flame photometric detection (HS-SPME-GC/PFPD). Multivariate analysis of variance (MANOVA) showed that vintage year, irrigation, and nitrogen can affect volatile sulfur compounds (p<0.01). Foliar nitrogen supplementation or soil nitrogen application significantly increased the contents of H2S (p<0.01) and methanethiol (MeSH) (p<0.01) in Pinot noir wines. Irrigation treatment yielded higher H2S and MeSH than non-irrigation treatment, and with tillage treatments also yielded higher H2S and MeSH. ANOVA demonstrated the interaction factor (irrigation×nitrogen) had significant impact on concentration of H2S and MeSH in wines. The combination of irrigation and soil nitrogen supplement had the highest amount of both H2S and MeSH. Dimethyl sulfide (DMS), methionol, methyl thioacetate (MeSOAc), and ethyl thioacetate (EtSOAc) were mainly affected by vintage.

Fire blight resistance, irrigation and conducive wet weather improve Erwinia amylovora winter survival in cankers.

Erwinia amylovora causes fire blight, a disease responsible for enormous economic losses in the pome fruit-producing areas where it is present. Despite the abundant research on fire blight, information about E. amylovora population dynamics and survival in fire blight cankers and the plant defense responses to this pathogen in the infected bark are limited. In our study, we obtained fire blight cankers in apple, pear, and Asian pear cultivars showing differing resistance to the disease by shoot inoculation with E. amylovora. We collected cankers from irrigated and non-irrigated trees every 3 months in two independent field experiments and analyzed samples by viability digital PCR. We also assessed the expression of pathogenicity-related (PR) genes in the bark of selected apple and Asian pear cultivars. A logistic regression analysis revealed the impact of environmental and host factors on E. amylovora detection rates in cankers. The chances of detecting live E. amylovora cells in cankers increased significantly in those collected from irrigated trees, in July, and/or during an experiment performed in a year with an expected average rainfall when compared to samples from non-irrigated trees, collected in January, and/or during an experiment performed under environmental conditions dominated by drought. We found a positive correlation between the pathogen detection rates in cankers and the host resistance to fire blight that might be explained by lower E. amylovora survival rates in more damaged tissues of susceptible hosts. The genes PR-1, PR-2, PR-5, and PR-8 were induced in the bark surrounding apple and Asian pear fire blight cankers. Our study, involving the analysis of more than 800 canker samples, provides new knowledge about the fire blight disease cycle and lays the foundation for improved fire blight management and eradication strategies in pome fruit orchards.

Proper management of irrigation and nitrogen-application increases crop N-uptake efficiency and reduces nitrate leaching

ABSTRACT Irrigation is, on one hand, expected to increase the risk of nitrate leaching through increased rates of percolation, but, on the other hand, enhances plant nutrient uptake and growth, thereby limiting the risk of leaching. To investigate this dichotomy, we analysed the effects of irrigation at three nitrogen (N)-application rates in spring barley (Hordeum distichum L., two experiments with 50, 100, and 150 kg N ha−1) and winter oilseed rape (Brassica napus L., one experiment with 50, 150, and 250 kg N ha−1) on a coarse sandy soil in Denmark in a humid climate, which facilitates nitrate leaching. Analyses comprised grain/seed dry matter yield, N-uptake, nitrogen use efficiency (partial nitrogen budget, PNB, and partial-factor productivity, PFP) and nitrate leaching. For both crops, increasing N-application without consideration of the crops’ drought-stress responses lead to a relatively lower N-uptake in grain, lower yield, lower PNB and PFP and higher nitrate leaching, although responses were not proportionally to increasing N-application. The effect of irrigation at the lowest N-rates was limited. The non-irrigated treatments with the highest N-rates had a grain/seed yield of 3.2, 2.3 and 0.7 t ha−1 and nitrate leaching rates of 64, 72 and 127 kg N ha−1 compared to a grain/seed yield of 5.3, 5.0 and 2.6 kg N ha−1 and nitrate leaching rates of 61, 42 and 85 kg N ha−1 (for spring barley, spring barley and winter oilseed rape, respectively). These results show that synchronised management of both irrigation and N-application are essential for reducing the risk of nitrate leaching and to promote efficient crop N-uptake in periods of droughts.

The Influence of Precision Dripping Irrigation System on the Phenology and Yield Indices of Sweet Maize Hybrids

Sweet maize is an annual plant that is extremely useful and economical for planting and harvesting. However, maize stands are damaged quickly in the case of nutrient and water deficiency. This research was carried out under dripping irrigation conditions and control plots without irrigation, involving seven different maize hybrids. The obtained results showed no existing variation in the dry matter content of cob (DMC) between the irrigated and non-irrigated treatments. Correlation analysis showed that increasing DMC causes decreasing moisture content of cob (MC) of sweet maize with irrigated and non-irrigated treatments. DMC and MC are important factors in the yield index on irrigation treatments. Biplots showed that the Dessert R72 (10.82) hybrid had maximum yield and effect on Brix/Abbe and Brix/Atago Pal-1, while the Messenger hybrids (42.96) had maximum effect on MC. It was also shown that DMC and MC are important factors in the yield index on irrigation treatments on hybrids. The Noa (37.97) and Honey hybrids (27.88) had minimum effect and performance on non-irrigation and irrigation treatments. The Messenger (11.25) and SF1379 hybrids (10.5) had a maximum performance on Brix Abbe and Brix Pal in the irrigation treatment and Dessert R78 (13.5), the Messenger hybrid (11.8) had a maximum performance on Brix/Abbe and Brix/Atago Pal-1 in non-irrigation treatment. The Dessert R78 (13.5) is the best-performing hybrid in terms of the yield of Brix/Abbe and Brix/Atago Pal-1 in the performed irrigation treatments.

Water status and thermal response of lime trees to irrigation and shade screen

Most lime trees are cultivated under open-field conditions. However, in the Mediterranean area some growers use shade screen to protect their orchards against abiotic and biotic stresses, inducing changes in the plant’s surrounding microclimate that could affect its water status. This field experiment focuses on the effect of shade screen (high density polyethylene white net with 76% light transmission) and irrigation on plant and soil water status of Bearss lime trees. Two irrigation treatments were applied during the summer-autumn to open-field and shaded lime trees: irrigated (control) and non-irrigated (stress). Volumetric soil water content (θv), air temperature (Ta) and canopy temperature (Tc) were real-time monitored and several derived thermal indices were calculated. Stem water potential (Ψstem) and leaf gas exchange: net photosynthesis (Pn) and stomatal conductance (gs) were measured on representative days. Withholding irrigation caused a gradual decline in soil and plant water status. θv decreased from the outset in the non-irrigated treatments, showing breaking point connecting the rapid and the slower soil drying processes. Significant differences in Ψstem, and gs values were observed between controls and stressed trees 15 days after stress initiation. During early stages of water stress, lime trees cultivated in open-field showed lower values of soil and plant water status than those grown in shaded conditions. However, at the end of stress period, similar values were noted for both cropping systems, pointing to severe water deficit. Tc and Tc-Ta values reflected the current lime tree water status. The soil water content sensors anticipated the plant water stress situation respect to thermal ones. The higher θv, Ψstem, gs, Pn and Tc values registered in shaded lime trees revealed that shading allowed better soil-plant water status and a 12-day window of opportunity to respond to the imposed soil water deficits. Threshold thermal-based values are proposed for precise irrigation management of lime trees in open-field and shaded conditions.

Soil Microorganisms and Seaweed Application With Supplementary Irrigation Improved Physiological Traits and Yield of Two Dryland Wheat Cultivars.

To evaluate the effect of useful soil microorganisms and organic compounds on physiological characteristics and yield of two wheat cultivars under supplementary irrigation conditions, a study was conducted in the Agriculture Research Farm of Kurdistan University during the two cropping seasons of 2017–2018 and 2018–2019. A split–split plot-based study on a randomized complete block design with four replicates was used as an experimental design. The main factor was irrigation at three levels, including control without irrigation, supplementary irrigation in the booting stage, and supplementary irrigation in the booting and flowering stages. Two wheat cultivars, namely, Sardari and Sirvan, as sub-factors and application of bio-fertilizers in eight levels, including the use of bio-fertilizers containing: Mycorrhiza, Seaweed extract, Nitrozist and Phosphozist, Mycorrhiza + Nitrozist and Phosphozist, Seaweed extract + Nitrozist and Phosphozist, Mycorrhiza + Seaweed extract, Mycorrhiza + Nitrozist and Phosphozist + Seaweed extract, and non-application of bio-fertilizers, were considered as sub-factors. The results of both seasons of the experiment showed that the application of bio-fertilizers compared to the control treatment at all irrigation levels increased root volume, leaf relative water content (RWC), membrane stability index (MSI), and photosynthetic pigment content. The highest amount of H2O2, proline, and soluble carbohydrates were obtained in wheat under dry land conditions, and supplementary irrigation, especially two-time irrigation, significantly reduced the values of these traits. Supplementary irrigation also increased grain yield, so that in the conditions of two-time irrigation compared to the non-irrigation treatment (dry land), in the first and second seasons, the grain yield increased by 79.51 and 78.69%, respectively. Application of bio-fertilizers (Mycorrhiza + Nitrozist and Phosphozist + Seaweed extract) in comparison with the non-application of these fertilizers, due to increased root volume, RWC, MSI, and content of photosynthetic pigments, increased the grain yield in the first and second seasons of the experiment by 8.04 and 6.96%, respectively. As a result, suitable microorganisms and seaweed can improve wheat resistance mechanisms to water deficit, which along with using supplementary irrigation that saves water consumption improves plant growth and yield in areas faced with water shortage.

Crop Assurance Strategies for Irrigated Grain Sorghum Production

This sprinkler-irrigated study was conducted from 2018 to 2021 at the Kansas State University Northwest Research-Extension Center near Colby, KS, to evaluate four different water management strategies that could provide assurance of adequateyielding grain sorghum. The grain sorghum was grown on sites with good initial soil water at planting (>70% of field capacity within the 8-ft deep silt loam profile). Strategies were 1) No seasonal irrigation; 2) Irrigation of 100% of ET minus Rain after the boot stage through remainder of season; 3) Irrigation of 100% of ET minus Rain up to a limit of 6 inches; and 4) Irrigation of 100% of ET minus Rain up to a limit of 3 inches. Cropping season rainfall ranged from 5.48 inches to 13.98 inches and irrigation ranged from 0 to 11 inches across strategies for the 4 years of the study. Yield increases due to irrigation varied across years, ranging from -3.6 bu/a to 21.2 bu/a, but averaged only 7.2 bu/a over the non-irrigated treatment. Average yields were 138, 143, 144, and 145 bu/a for the four respective water management strategies. Soil water extraction by the grain sorghum was greater in the drier years and increased with less applied irrigation. These results indicate that adequately-yielding grain sorghum can be produced on sites with good soil water profiles at planting with little (≈ 3 inches) or even no in-season irrigation.

Short-term stem diameter variations in irrigated and non-irrigated stone pine (Pinus pinea L.) trees in a xeric non-native environment

Irrigation of adult stone pine trees growing in a xeric non-native habitat had positive effects not only in stem diameter growth but also in tree response to climatic variability. Stone pine is a key species from Mediterranean Europe increasingly planted in South America. The knowledge about irrigation impact on short-term stem diameter dynamics is still limited in non-native arid areas. To improve our understanding of the effect of irrigation on (1) stem diameter changes of stone pine trees in a drought-prone environment in Chile and (2) the sensitivity of the species to weather conditions. We studied daily stem diameter changes in irrigated and non-irrigated 31-year-old stone pine trees during a growing season with below average precipitation in Chile. Short-term diameter changes were recorded using high-resolution dendrometers. The detrended daily stem diameter changes, expressing tree water status, were correlated with weather variability in both irrigated and non-irrigated trees. The growth period lasted longer and the cumulative sum of daily changes increased by 130% in irrigated trees. Moreover, a similar correlation of tree water status with climatic variables was found in non-irrigated, with the exception of precipitation. Irrigation increased stone pine productivity in this xeric environment and reduced the correlations between daily stem diameter variations and local climatic variability.