Summer Irrigation Research Articles

Induction and potential role of summer dormancy to enhance persistence of perennial grasses under warmer climates

Abstract The persistence of perennial herbaceous species is threatened by increasing aridity. However, summer dormancy is a strategy conferring superior survival to grasses adapted to hot and dry summers. The role of temperature on the induction of summer dormancy was investigated in the perennial grass Dactylis glomerata to analyse the potential expression of this strategy under warmer climates. We tested seven populations of D. glomerata originating from Morocco to Norway across the same latitudinal gradient in a five‐site experiment. One population of the highly summer‐dormant grass Poa bulbosa was used as a reference. Plants were grown from autumn in pots under full irrigation for 1 year mostly under open‐air shelters. Heading date (ear emergence preceding flowering) was recorded and foliage senescence was assessed from end of spring until autumn. The maximum plant senescence under summer irrigation indicated the level of dormancy expression. Summer dormancy onset, release, expression and duration were modelled as a function of climatic variables. From north to south, the duration of summer dormancy of the Mediterranean populations of D. glomerata and P. bulbosa ranged from 0 to 122 days, and 79 to 200 days, respectively. P. bulbosa was always completely dormant, while dormancy expression of D. glomerata was positively correlated with the sum of temperatures from winter onset (R2 = 0.57) and with the mean of minimum temperatures in summer (R2 = 0.73). Dormancy onset, release and duration were also positively correlated with thermal time from winter onset, while the duration of summer dormancy was longer as maximum temperatures increased. Mapping the European regions with climates allowing the expression of summer dormancy in D. glomerata showed that the potentially inductive areas for this strategy may expand in parallel with increasing summer aridity under a future climate warming scenario. Synthesis. The large phenotypic variability of the expression of summer dormancy in D. glomerata was driven by temperature, suggesting that this strategy may have a greater role in higher latitudes to increase plant survival over the predicted hotter and drier summers. Leveraging this strategy for the choice and selection of suitable populations could enhance future adaptation of major perennial grasses to climate change.

Deep soil nitrogen storage slows nitrate leaching through the vadose zone

Nitrogen (N) fertilizer applications are important for agricultural yield, yet not all the applied N is taken up by crops, leading to surplus N storage in soil or leaching to groundwater and surface water. Leaching loss of fertilizer N represents a cost for farmers and has consequences for human health and the environment, especially in the southern Willamette Valley, Oregon, USA, where groundwater nitrate contamination is prevalent. While improved nutrient management and conservation practices have been implemented to minimize leaching, nitrate levels in groundwater continue to increase in many long-term monitoring wells. To elucidate controls on leaching rates and N dynamics in agricultural soils across soil depths, and in response to seasonal and annual variation in management (e.g., fertilizer input amount and summer irrigation), we intensively monitored the transport of water and nitrate every two weeks for four years through the vadose zone at three depths (0.8, 1.5, and 3.0 m) in a sweet corn (maize) field. Though nitrate leaching was highly variable among lysimeters at the same depth and across years, a strong pattern emerged: annual nitrate leaching significantly decreased with depth across the study, averaging ~104 kg N ha-1 yr-1 near the surface (0.8 m) versus ~56 kg N ha-1 yr-1 in the deep soil (3.0 m), a 54% reduction in leaching between the soil layers. Even though crops were irrigated in summer, most leaching (~72% below 3.0 m) occurred during the wet fall and winter. Based on steady state assumptions, a net equivalent of ~29% of surface N inputs leached below 3.0 m into the deeper soil and groundwater, while ~44% was removed in crop harvest, indicating considerable N retention in the soil (~27% of inputs or approximately 58 kg N ha-1 yr-1). The accumulation and long-term dynamics of deep soil N is a legacy of agricultural management that should be further studied to better manage and reduce nitrate loss to groundwater.

Water-conscious management strategies reduce per-yield irrigation and soil emissions of CO2, N2O, and NO in high-temperature forage cropping systems

Agricultural soils are important sources of greenhouse gases carbon dioxide (CO2) and nitrous oxide (N2O), as well as nitric oxide (NO), a precursor to tropospheric ozone. Management approaches that constrain these emissions can limit future warming and improve regional air quality, especially in high-temperature agroecosystems where soil emissions are high. Subsurface drip irrigation is a promising management solution that can limit emissions via targeted rhizosphere access to water and nitrogenous fertilizers. In complementary field studies in southern California, we compared per-yield irrigation and soil emissions in surface- and drip-irrigated field plots growing alfalfa (Medicago sativa L.) and sudangrass (Sorghum bicolor ssp. Sudanese), two forage crops with differing fertilizer requirements. For each study, we monitored soil temperature, moisture, and emission responses to irrigation in both spring and summer using a custom automated chamber array that recorded measurements every 30 minutes. We found that, compared to furrow irrigation, drip irrigation in sudangrass increased hay yield by 6% and per-yield soil CO2 emissions by 9% while it decreased irrigation demand by 49%, N2O emissions by 59%, and NO by 49%. In alfalfa, drip irrigation increased yield by 7% while decreasing irrigation by 1%, per-yield soil CO2 emissions by 59%, N2O by 38%, and NO by 20%. In both crops, differences between irrigation types were strongest in summer months, when high temperatures produced large pulses of N2O and NO in sudangrass and CO2 in alfalfa following flood irrigation relative to small pulses following drip irrigation. As agriculture intensifies in warmer climates, implementation of subsurface drip irrigation can help reduce the emission of soil emissions that affect Earth’s climate and regional air quality.

Perceptions on irrigation water supply and utilisation by smallholder agricultural enterprises in Vhembe district of Limpopo Province, South Africa

The study investigated perceptions on irrigation water supply and utilisation by Smallholder Agricultural Enterprises (SHAEs) in the Vhembe District of Limpopo Province. More (55.4%) SHAEs depended on surface water as the main source for irrigation. Surface water supply was ranked moderate in the majority of SHAEs, both for summer (58.6%) and winter (69.7%) irrigation and was regarded as always available (51.3%). Groundwater was the main source in 44.2% of SHAEs and was ranked very high for summer (55.7%) and winter (34.4%) irrigation. Groundwater was perceived to have the advantage of being always available in 83.6% of SHAEs while 64.9% complained about higher pumping costs. One in three (33.9%) SHAEs revealed they irrigated two to four times a day while one in five (18.7%) irrigated once every eight to 14 days. The mean amount of water used to irrigate was estimated at 5 300,88l +/- 20 762,91l. Almost two in three (62.6%) SHAEs experienced competition for water. Statistically, signification association was observed between the main source for irrigation and monthly income (X2 (1) = 7.10, p < 0.013) after the Bonferroni adjustment. It was determined that 51,3% of SHAEs with income </= R5000/month used surface water as the main source for irrigation compared to 69.6% with income > R5000/month.

Effects of irrigation-fertilization-tillage on nutrient loading and crop yield in Ulansuhai watershed based on improved SWAT model

不合理的灌溉、施肥和耕作是导致乌梁素海流域农业面源污染的主要根源，乌梁素海作为我国北方地区重要的生态安全屏障，多年来面临着湖泊水环境污染、水生态退化等问题，科学开展湖泊水环境综合治理首先要解决流域内农业面源污染问题. 研究通过修改土壤水平衡、溶质平衡、地下水平衡和作物生长等模块对SWAT 2012原始版本进行改进，并采用改进的SWAT模型构建了乌梁素海流域分布式水文模型，利用实测径流、硝态氮与总磷排放量、地下水埋深以及作物产量校正和验证模型. 基于现状情景，以玉米、葵花和小麦3种主要作物为研究对象，设置了削减灌水量、施肥量及调整耕作方式3种农田管理情景. 基于改进SWAT模型不同情景的模拟结果，计算分析各管理情景下的硝态氮与总磷负荷及对各作物产量的影响. 结果表明，改进SWAT模型具有良好的模拟效果. 不同作物削减5%夏灌水量增产最多达8.41%~10.32%，削减10%秋浇水量均明显减少硝态氮和总磷负荷. 不同作物营养物负荷均随着氮磷施肥削减比例的增大呈现逐渐降低的趋势，但下降曲线逐渐趋于平缓; 各作物产量随氮磷施肥削减比例的增加呈先增加后减少的趋势，其中玉米、小麦氮磷施肥削减比例达20%时产量开始下降，葵花氮磷施肥削减比例达25%时产量开始下降. 不同作物营养物负荷与小麦产量均随耕作方式混合深度与混合效率参数的增大逐渐减小，而玉米和葵花产量则随耕作参数增大逐渐增加. 综合分析，削减5%夏灌水量+削减20%氮磷施肥比例+模板犁耕作组合玉米产量增幅最大达36.5%;削减10%秋浇水量+削减25%氮磷施肥比例+模板犁耕作组合葵花硝态氮负荷降幅最大达42.1%;削减5%夏灌水量+削减20%氮磷施肥比例+免耕组合小麦产量增幅最大达29.1%;而削减5%秋浇水量+削减20%氮磷施肥比例+常规春耕组合小麦硝态氮负荷减少最大达27.2%，总磷负荷减少最大达18.5%. 本研究可为降低流域内面源污染、提高作物产量及减少乌梁素海营养物入湖负荷农业管理措施的实施提供理论依据.;Irrational irrigation, fertilization and farming are the main causes of agricultural non-point source pollution in Ulansuhai watershed. As an important ecological security barrier in northern China, Lake Ulansuhai has been facing problems, such as lake water environment pollution and water ecological degradation. To achieve the integrated management of lake water environment, agricultural non-point source pollution in the watershed must be controlled. The study improved the original version of SWAT 2012 by modifying the modules of soil water balance, solute balance, groundwater balance, and plant growth. A distributed hydrological model of Ulansuhai watershed was constructed with the improved SWAT model, which was calibrated and validated with measured runoff, nitrate nitrogen (NN), total phosphorus (TP) emissions, groundwater depth and crop yield. Three scenarios including reduced amount of irrigation, fertilization, and adjusted farming mode based on the current situation were applied on three main crops (corn, sunflower and wheat). NN and TP loadings and their effects on the crop yields under different management scenarios were simulated using the improved SWAT model. The results showed that the improved SWAT model has a good simulation fitting. For different crops, reducing the irrigation amount by 5% in summer can increase production by up to 8.41%-10.32%, and reducing 10% irrigation in autumn will significantly reduce the NN and TP loadings. The nutrient load of different crops showed a decreasing trend with an increasing reduction ratio of nitrogen and phosphorus fertilization (NPF), but the declining rate gradually became smaller. The yields of different crops increased first and then decreased with the ratio of NPF increase. When the ratio of NPF reduction reached 20%, the yield of corn and wheat began to decline, and when it reached 25% the yield of sunflower began to decline. The nutrient loads and wheat yield of different crops gradually decreased with an increase of the mixing depth and efficiency of the tillage mode, while the yield of corn and sunflower gradually increased with the tillage parameters. If combining cutting 5% of summer irrigation, reducing 20% NPF amount, and the template plowing combination, corn yield could increase by 36.5%. If cutting 10% of autumn watering, reducing 25% NPF, the template plowing combination, sunflower nitrate nitrogen load could reduce by 42.1%. If cutting 5% of summer irrigation, 20% reduction NPF, and no-tillage combination, wheat yield could increase by 29.1%. However, cutting 5% of autumn watering, 20% reduction NPF and conventional spring ploughing combination, NN loading of wheat farming could reduce by up to 27.2%, and TP loading could reduce by up to 18.5%. This research can provide a scientific basis for the implementation of agricultural management measures to reduce non-point source pollution, increase crop yields in Ulansuhai watershed and reduce the nutrients loads in Lake Ulansuhai.

تأثير الري التكميلي والتسميد الورقي ومنظم النمو NAA على تبادل الحمل لأشجار الفستق الحلبي Pistacia vera

هدفت هذه الدراسة إلى معرفة تأثير الري التكميلي، التسميد الورقي ومنظم النمو NAA على نسبة تساقط البراعم، الإنتاجية ونسبة تفتح الثمار في أشجار الفستق الحلبي. أجريت الدراسة خلال 2017-2020 على أشجار الفستق الحقيقي vera. L Pistacia (صنف عاشوري)، وصممت التجربة وفق القطع المنشقة من الدرجة الثانية Split Split Plot Design، حيث تضمنت القطع الرئيسية معاملات الري التكميلي (دون ري، رية شتوية، رية صيفية ، رية صيفية وشتوية)، والقطع من الدرجة الأولى تراكيز التسميد الورقي (0، 1 و 2 غم.لتر-1)، أما القطع من الدرجة الثانية فقد تضمنت مستويات NAA(0، 25 و 50 ppm). أشارت النتائج أن نسبة التساقط للبراعم الإبطية في مواسم الحمل أعلى من مواسم عدم الحمل وكان أخفضها في الموسم الثالث للأثر المشترك للتسميد (2 غم. لتر-1) و NAA (50ppm) وبلغت (30.9%)، تلتها معاملة NAA (50 ppm) وبلغت (31.2%). كما بلغ متوسط الإنتاجية أقصاها في عام الحمل للموسم الرابع (39.49 كغم) عند معاملة الري المشتركة (شتوية+ صيفية)، بينما كان في معاملة المقارنة (29.17 كغم)، وكان أعلى متوسط لنسبة الثمار المتفتحة في الموسم الرابع للأثر المشترك عند معاملة الري المشتركة ومستوى التسميد (1غم.لتر-1) وبلغت (97.1%)، تلتها معاملة الري المشتركة وبلغت نسبة الثمار المتفتحة (96.77%).

TRANSFORMATION OF FLOODPLAIN LANDSCAPES UNDER THE INFLUENCE OF NATURAL AND ANTHROPOGENIC CHANGES IN THE ENVIRONMENT (ON THE EXAMPLE OF THE ZAKHARKOVO FLOODPLAIN OF THE MOSCOW RIVER)

The Zakharkovskaya floodplain of the Moscow River is located directly above the Moscow Ring Road. It is an example of a natural structure that is spontaneously restored after long-term economic use (hayfields, pastures, long-term plowing, summer cottege settlements, drainage and irrigation channels, silt sites, etc.) under conditions of cessation of intensive anthropogenic impact. The article deals with the history of the formation and development of the Zakharkovskaya floodplain in prehistoric times (late Holocene), in the early historical period (beginning-middle of the second millennium AD), and in the late historical period-XIX-XXI centuries. The regulation of water flow, which has occurred in recent decades, is accompanied by a relative stabilization of the Moscow riverbed, turning it into a canal, reducing the intensity of channel deformations, leveling the bottom relief with its general deepening. As in other floodplain plots, the territory of floodplain leaves the flood zone; depressions are filled in, lakes are degraded, and man-made terrain is formed. At the same time, the current restrictions on access to the territory of the Zakharkovskaya floodplain for 10-15 years have created conditions for the restoration of natural structures, in particular, forest and shrub tracts, and increased the landscape and ecological attractiveness of floodplain lands.

The iCOLT climate service: Seasonal predictions of irrigation for Emilia‐Romagna, Italy

AbstractEmilia‐Romagna is a region of Northern Italy whose land use is mainly devoted to agriculture, especially over the plain area. Since the region is characterized by summer water shortages and recurrent drought conditions, a summer irrigation water demand forecast system has been developed, operating both at regional and Land Reclamation and Irrigation Board levels. Remote sensing crop detection is used in combination with a soil water balance model as a monitoring tool in support to water management and to optimize the use of available water resources. These instruments are also integrated with operational calibrated probabilistic seasonal forecast products currently based on Copernicus Climate Services, in order to evaluate summer irrigation water needs in advance in support to decision‐making by water managers. Results obtained using this prediction system are characterized by a significant forecast skill. The sources of the predictability of this system are specifically evaluated, showing that the correct representation of crop geographical distribution is crucial for the ability of the system to capture spatial variability in irrigation demand. Furthermore, the system forecast skill is mostly due to the use of an empirical model to assess the hypodermic water table depth initialized by means of the observed meteorological data of the months before the beginning of the summer season. Finally, calibrated probabilistic seasonal predictions also contribute to a minor extent to the good performance of the system as a whole.

Conventional subsoil irrigation techniques do not lower carbon emissions from drained peat meadows

Abstract. The focus of current water management in drained peatlands is to facilitate optimal drainage, which has led to soil subsidence and a strong increase in greenhouse gas (GHG) emissions. The Dutch land and water authorities proposed the application of subsoil irrigation (SSI) system on a large scale to potentially reduce GHG emissions, while maintaining high biomass production. Based on model results, the expectation was that SSI would reduce peat decomposition in summer by preventing groundwater tables (GWTs) from dropping below −60 cm. In 2017–2018, we evaluated the effects of SSI on GHG emissions (CO2, CH4, N2O) for four dairy farms on drained peat meadows in the Netherlands. Each farm had a treatment site with SSI installation and a control site drained only by ditches (ditch water level −60 / −90 cm, 100 m distance between ditches). The SSI system consisted of perforated pipes −70 cm from surface level with spacing of 5–6 m to improve drainage during winter–spring and irrigation in summer. GHG emissions were measured using closed chambers every 2–4 weeks for CO2, CH4 and N2O. Measured ecosystem respiration (Reco) only showed a small difference between SSI and control sites when the GWT of SSI sites were substantially higher than the control site (> 20 cm difference). Over all years and locations, however, there was no significant difference found, despite the 6–18 cm higher GWT in summer and 1–20 cm lower GWT in wet conditions at SSI sites. Differences in mean annual GWT remained low (< 5 cm). Direct comparison of measured N2O and CH4 fluxes between SSI and control sites did not show any significant differences. CO2 fluxes varied according to temperature and management events, while differences between control and SSI sites remained small. Therefore, there was no difference between the annual gap-filled net ecosystem exchange (NEE) of the SSI and control sites. The net ecosystem carbon balance (NECB) was on average 40 and 30 t CO2 ha−1 yr−1 in 2017 and 2018 on the SSI sites and 38 and 34 t CO2 ha−1 yr−1 in 2017 and 2018 on the control sites. This lack of SSI effect is probably because the GWT increase remains limited to deeper soil layers (60–120 cm depth), which contribute little to peat oxidation. We conclude that SSI modulates water table dynamics but fails to lower annual carbon emission. SSI seems unsuitable as a climate mitigation strategy. Future research should focus on potential effects of GWT manipulation in the uppermost organic layers (−30 cm and higher) on GHG emissions from drained peatlands.

Projection of the climate change effects on soil water dynamics of summer maize grown in water repellent soils using APSIM and HYDRUS-1D models

Soil water repellency greatly affects crop growth and soil water movement. The aim of this study was to estimate dynamics of soil water storage (SWS), actual evapotranspiration (ETa), root water uptake (RWU) and actual evaporation (Ea) under an annual crop grown in water repellent (WR) soils at future climate scenarios. The soil hydraulic parameters were calibrated and validated for HYDRUS-1D based on the experimental data in 2016 and 2017. The summer maize growth periods and irrigation schedules were generated with Agricultural Production Systems Simulator (APSIM). The daily SWS, ETa, RWU and Ea values from five water repellent treatments were simulated for summer maize growth periods during 1981–2000, 2030–2059 and 2060–2089 using eight selected global climate models under two representative concentration pathways (RCP 4.5 and RCP 8.5). Due to the increased temperature, the growth period reduced by 12–27 days, the total SWS, ETa, RWU and Ea decreased by 8.1%-21.1%, 2.2%-11.1%, 0.5%-9.7% and 0.8%-9.6% compared to the baseline period, respectively. Changes of total SWS, ETa, RWU and Ea during the whole summer maize growth periods under RCP 4.5 were greater than RCP 8.5 during the same period. Values of total SWS, ETa, RWU and Ea in 2030–2059 were higher than 2060–2089 for the same RCP scenario. With increasing initial water droplet penetration time, total SWS and Ea increased, while ETa and RWU decreased. The global circulation model (GCM) and Period contributed greatly to uncertainty. The results implied that it is necessary to adjust the planting date of summer maize.

Radiation use efficiency, biomass production and grain yield of heat tolerant summer maize (Zea mays L.) hybrids in subtropical environment

Radiation use efficiency (RUE), heat use efficiency (HUE), biomass production and grain yield of contrasting heat tolerant summer maize hybrids and irrigation regimes during hot summer in subtropics of India were assessed. Experiment was conducted with RCRMH-1, RCRMH-2 and Arjun hybrids under well-watered based on 1.0 IW/CPE (I1), mild stress at 0.75 IW/CPE (I2) and severe stress at 0.5 IW/CPE (I3). Results indicated that RCRMH-2 outyielded 13.3 and 26.4% over RCRMH1 and Arjun, respectively. In well-watered (I1) plots all the hybrids performed better than other irrigation regimes I2 and I3. Among hybrids RCRMH-2 showed lower grain yield reduction under water stress condition. While RUE of RCRMH-2 under I1, I2 and I3 were 1.93, 1.72 and 1.53 g/MJ, respectively. It also showed higher biomass production, LAI and HUE over rest of the hybrids. Radiation, water and heat use efficiencies, yield attributes and yield were higher in January sown plants.

Drip irrigation provides a trade-off between yield and nutritional quality of tomato in the solar greenhouse

To address the twin issues of food and nutrition security, the focus of agricultural production should be shifted from biomass productivity to nutritional gains. The objectives of this study were to evaluate the impact of conversion from furrow to drip irrigation on the yield components, water productivity (WP), nutritional yield (NY) and nutritional water productivity (NWP) of tomato during two consecutive growth cycles (2017–2018) in a greenhouse in the arid area of Northwest China. Results showed that the environment under drip irrigation was more beneficial to the accumulation of phytochemicals and the formation of total antioxidant activity in tomato fruits, which also significantly increased the NWP. However, the notable decline in single fruit fresh weight reducing the tomato yield significantly under drip irrigation in summer, while the WP and NY were similar to furrow irrigation. This indicated that the NY of tomato was mainly determined by the fruit yield, while the NWP was strongly affected by the mass concentration of nutrients. In contrast, no difference was found in the single fruit fresh weight and tomato yield between drip and furrow irrigation in winter, which related to the similar environmental conditions, while the WP and NY were significantly higher under drip irrigation. In summary, the potential and water use efficiency in nutrient production of tomato were enhanced under drip irrigation, and the improvement of fruit quality can offset the negative effect of yield reduction. Therefore, drip irrigation can achieve a good balance between the high yield and superior quality of tomato fruits, meanwhile reducing the pressure on the environment caused by horticultural production. We propose that the drip irrigation should be employed in the greenhouse in arid areas for tomato production, and the concepts of NY and NWP can be further applied to other horticultural crops with high nutritional value.

Estimations and projections of Avena fatua dynamics under multiple management scenarios in crop fields using simplified longitudinal monitoring

Integrated weed management (IWM) is currently the most appropriate and effective method of agricultural weed control. To determine the most effective strategy, it is necessary to compare the effects of different control options and their rotation. Avena fatua (common wild oat) is one of the most common and economically threatening grass weed species of cereal crops worldwide. To examine the effects of non-chemical weed management options (farmland use, delayed sowing, and summer irrigation) on control of A. fatua, we recorded coverage levels and field conditions in 41 sites during the spring growing season of winter wheat for about 10 years. A transition matrix model was then constructed to project coverage levels of A. fatua under each management option using ordinal logistic regression. The results showed that farmland use had a remarkable effect on coverage; notably, planting of paddy rice and vegetables, which respectively eliminated the effect of coverage in the previous year and facilitated rapid convergence of coverage to 0%. Thus, although 90% of fields under continuous wheat cultivation were found to be at risk of A. fatua colonization, the risk was reduced to almost 0% with rotation of effective farmland use. As summer irrigation was also effective, more than 50% of wheat fields with the option continuously converged to no risk for A. fatua colonization. When the different management cycles were repeated, the effects were observed within 3 years, with a steady state reached in less than 10 years. Overall, these results suggest that simplified monitoring data could help decision-making on IWM, thereby helping to improve the efficiency of agricultural production.

Effect of Moisture Regimes on Water use Efficiency of Rabi / Summer Groundnut Genotypes in Northern Transition Zone of Karnataka

Background: During rabi / summer irrigation water is a scarce resource, but crop needs more water due to non-rainy season and warmer climate. Hence, a field experiment was conducted during rabi / summer season of 2016-17 to study the effect of irrigation water regimes on water use efficiency (WUE) of groundnut genotypes in Northern Transition Zone of Karnataka. Methods: This field study comprised of four main plots as water regimes viz. I1: (control) seven irrigations at 15 days interval from sowing to 105 DAS, I2: Stress at pegging stage; withdrawal of one irrigation between 45 - 60 DAS, I3: Stress at pegging and pod filling stage; withdrawal of two irrigations between 45-75 DAS, I4: Stress at pegging, pod filling and kernel development stage; withdrawal of four irrigations from 45-105 DAS and four genotypes as sub plots viz. G1: Dh-86, G2: Dh-101, G3: K-9 and G4: G2-52. Treatments were replicated thrice and laid out in split plot design. Result: Among the water regime, I2 recorded significantly higher WUE (6.2 kg ha-1 mm-1) followed by I1 (control; 5.5 kg ha-1 mm-1). Water regime I2 also recorded significantly higher pod yield and haulm yield (2,857 kg ha-1 4,648 kg ha-1, respectively) along with other yield attributes, but was found at par with control (I1). This study showed that WUE as well as yield of rabi / summer groundnut can be enhanced if crop was exposed only to mild stress by skipping an irrigation at pegging stage out of total seven irrigations. Among the genotypes, Dh-86 with 2,375 kg ha-1 of pod yield performed significantly better over others like Dh-101 (2,215 kg ha-1), K-9 (2,048 kg ha-1) and G2-52 (1,880kg ha-1) suggesting differential response to moisture stress, thus choice of moisture stress tolerant genotypes is equally important to enhance WUE. Interaction between irrigation regime and genotypes showed that Dh-86 (G1) with I2 irrigation regime recorded significantly higher WUE (6.9 kg ha-1 mm-1), pod yield (3,168 kg ha-1) and net return (Rs. 95,655 ha-1) and was found at par with full irrigation regime (I1).

Seasonal variation and driving factors of carbon and nitrogen stable isotope values of plankton in four lakes of Yunnan Province

浮游生物是湖泊食物网的重要组成，其碳、氮稳定同位素能够反映元素地球化学循环和食物来源的波动，是了解水域生态系统结构变化的重要手段之一.本文选取云南4个不同类型湖泊，开展浮游生物碳、氮稳定同位素组成（δ¹³C、δ¹⁵N）的季节变化与湖泊对比研究.大型深水湖泊（抚仙湖和阳宗海）中，浮游植物δ¹³C值在夏、秋季（-20.34‰±1.98‰）显著高于冬、春季（-28.00‰±2.51‰），反映夏秋季藻类生长速率较高、HCO₃^-无机碳源利用增多等的影响.而小型浅水湖泊（长桥海和大屯海）中浮游植物δ¹³C值在夏季最高（-21.24‰±0.88‰），可能与雨季流域输入增强、陆源有机质占比增加有关.4个湖泊浮游生物δ¹⁵N值具有一致的变化特征，春季显著高于其他季节.分析表明，云南地区雨季以面源污染为主向旱季以点源污染为主的转变，导致氮素营养盐季节性来源差异，并通过生物吸收作用影响了浮游生物δ¹⁵N值的季节变化.在浮游动物与浮游植物的稳定同位素差值（即富集度）方面，营养水平高的小型浅水湖泊中δ¹³C富集度为1.61‰±0.90‰、δ¹⁵N富集度为2.71‰±1.22‰，显著小于营养水平低的大型深水湖泊（分别为2.60‰±0.98‰和4.19‰±1.25‰），表明随着湖泊营养水平的增加，浮游动物更多地以浮游植物为食，导致有机碳在不同营养级之间的传输过程中具有更强的耦合作用，且相邻营养级之间具有更低的δ¹⁵N富集度特征.;Plankton is an important component of lake food webs. Their carbon and nitrogen stable isotope values can reflect the fluctuation of biogeochemical cycling and food sources and can be applied to track the changes of aquatic ecosystem structure. In this paper, four lakes with distinct typology from Yunnan Province were selected to uncover the seasonal changes in carbon and nitrogen stable isotopic compositions of plankton. The carbon stable isotope values of phytoplankton in large deep lakes (Lake Fuxian and Lake Yangzong) are enriched in summer and autumn (mean ±SD: -20.34‰±1.98‰), but relatively depleted in winter and spring (-28.00‰±2.51‰), which may reflect a higher growth rate of plankton and greater assimilation of bicarbonate (HCO₃^-) during the growing season. In small shallow lakes (Lake Changqiao and Lake Datun), carbon stable isotopic values of phytoplankton are mostly enriched in summer (-21.24‰±0.88‰) among the four sampling seasons. This may be related to the increased input of terrigenous organic matter during the rainy season, and a decreased lower water level due to overuse of agricultural irrigation in summer. In contrast to the carbon stable isotope values, the nitrogen stable isotope composition of plankton displayed a similar trend of seasonal variations across lakes where a significantly more positive value was found in spring than in other seasons. Further analyses revealed that that seasonal variation in the nitrogen stable isotope of plankton is related to the seasonal difference of nitrogen sources and their distinct isotopic compositions. Specifically, non-point source pollution, mainly related to agricultural fertilizers with depleted nitrogen stable isotopic value, is often dominant in the rainy season, while point source pollution predominantly derived from sewage input with enriched nitrogen stable isotopic composition is commonly observed in the dry season. In terms of stable isotope fractionation between zooplankton and phytoplankton (i.e. trophic enrichment), small shallow lakes were characterized by smaller carbon (1.61‰±0.90‰) and nitrogen (2.71‰±1.22‰) stable isotopic enrichment than those in large deep lakes (2.60‰±0.98‰ and 4.19‰±1.25‰, respectively) in this study. Zooplankton often displays a higher degree of dependence on autochthonous organic carbon (such as phytoplankton) with increasing nutrient status, reflecting a stronger coupling of organic carbon transfer between trophic levels. Similarly, a smaller degree of nitrogen stable isotope enrichment is evidenced in more eutrophic lakes in this study.

A Novel Idea for Improving the Efficiency of Green Walls in Urban Environment (an Innovative Design and Technique)

The advantages of low-impact development approaches, such as green walls in an urban environment, are numerous. These systems can be applied for managing stormwater, saving energy consumption, decreasing noise pollution, improving runoff quality, improving life quality, and so forth. Besides, atmospheric water harvesting methods are considered a nonconventional water source. There are many studies about the analysis and advantages of green walls and atmospheric water harvesting conducted separately. However, the use of a combined system that uses fog harvesting in the irrigation of green walls has received less attention in previous studies, and therefore in this research, the feasibility of a novel green wall platform was investigated. At first, the potential of using green walls and atmospheric water harvesting in different climates was analyzed. Then a new combined system was proposed and explained. The study results determined that atmospheric water harvesting can be applied as a source of irrigation for green facilities, particularly in the dry season and in periods with lower precipitation. In the Mediterranean climate, summer fog harvesting yields 1.4–4.6 L/m2/day, and the water consumption of green walls is about 4–8 L/day/m2. This can improve one issue of green walls in an urban environment, which is irrigation in summer. Furthermore, the novel system would protect plants from severe conditions, improve buildings’ thermal behavior by decreasing direct sunlight, and increase conventional green walls’ efficiency and advantages.

Management options for improved survival of perennial ryegrass (

In northern Victoria, Australia, perennial pastures for the dairy industry have historically been based on perennial ryegrass. However, perennial ryegrass does not perform well under high summer temperatures and water stress. We investigated irrigation, renovation and grazing management strategies for improving the resilience and survival of perennial ryegrass over summer on two farms in northern Victoria over 2.5 years. At each farm, two irrigation bays were sown in March 2015. During summer (late December–mid-March), one bay was not irrigated and the other bay received a single mid-summer irrigation. Each bay was sown to 12 ryegrass cultures: five cultivars of perennial ryegrass either oversown or not oversown, and two oversown cultivars of short-lived ryegrass (SLRG). A mid-summer grazing treatment was applied to one-half of each of these plots. All plots at both sites received the same irrigation and grazing management at other times of the year. There were significant variations in dry matter (DM) production, nutritive characteristics and plant frequencies across sites and seasons, and across renovation, irrigation and grazing management strategies. Cumulative DM yields were higher in the perennial ryegrass than the SLRG cultivars. Summer DM removal was very low at both sites; the ungrazed plots recovered and produced more DM in the following cooler period than the grazed plots in the first year but not the second. Metabolisable energy concentration was higher for perennial ryegrass than SLRG cultivars and was also higher in plots that had been grazed over the summer. There were large differences in plant frequency between species, and there were some differences among perennial ryegrass cultivars. The effect of summer grazing on plant frequency varied at each site and was not significant within an irrigation treatment. This research confirms that perennial ryegrass is not well suited to the hot, dry summers of northern Victoria and suggests that, under conditions of limited summer irrigation, farmers should focus on plant survival rather than summer yield if they are to maximise annual DM production.

Summer irrigation of pasture enhances the transfer and short-term storage of soil organic carbon in the particulate and mineral-associated organic matter fractions

Soil organic carbon (SOC) is both a source and sink of atmospheric carbon dioxide (CO2), with important implications for global climate change. Irrigation of grazed pastures has reportedly increased, reduced or made no difference to SOC stocks relative to dryland management. This study examined, over an annual plant growth cycle, the persistence of photosynthate-derived carbon (C) previously allocated to the plant–soil system during summer, under irrigated or dryland conditions. A continuous 13CO2 pulse labelling method was used to label ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) mesocosms under simulated dryland or irrigated conditions. Plant and soil 13C was traced over 349 days using destructive sampling on days 1, 12, 125, 237 and 349 (T1–T5 respectively). After the cessation of labelling and summer irrigation, the mesocosms were maintained under the same seasonal soil moisture conditions. The persistence of 13C in the aboveground plant C pools was lower than in the root C pool. Approximately 50% of the initial mass of 13C recovered in roots at T1 remained by T5. There was no difference between the summer irrigated and dryland treatments in terms of the 13C recovered from the soil over the subsequent annual growing season. There was also no significant change in the 13C recovered in the soil between T1 and T5. However, summer irrigation did affect the spatial and temporal distribution of the photosynthate-derived C within the soil size fractions relative to summer dryland conditions. Summer irrigation promoted the transfer and storage of 13C in the fine particulate organic matter and clay size fractions.

Does summer irrigation alter nitrogen uptake and utilisation efficiency of saffron (Crocus sativus L.) for different organic and chemical fertilisers?

ABSTRACT Nutrient loss is one of the most important problems in saffron cultivation which affects saffron production. Summer irrigation during flower initiation period improves saffron yield but affects nutrient availability. This study aimed to evaluate the role of summer irrigation on saffron nitrogen (N) uptake and utilisation efficiency for different organic and chemical fertilisers. A three-year field experiment was conducted as split-plot under a randomised complete block design with three replications. Main plots were included the summer irrigation and no-summer irrigation, subdivided to five sub-plots including chemical fertiliser, vermicompost, cow manure, chicken manure, and control. The measured criteria were corm N concentration, N uptake efficiency (NUpE), N utilisation efficiency (NUtE), agronomic N use efficiency (AgNUE) and saffron corm and flower yield parameters. The results revealed that organic manures improved corm NUpE, NUtE and AgNUE. Plants had the highest NUpE under cow manure and utilised N more efficiently, resulted in the highest NUtE and AgNUE. Summer irrigation had implications for different organic fertilisers with a positive effect on vermicompost but a negative effect on chicken manure and chemical fertiliser. Dry stigma and corm yield were higher in vermicompost than chicken manure under summer irrigation, while it decreased with chemical fertilisation.

Heavy Metals in Grey Mullet (Mugil cephalus) Fish Collected From Barseque Fish Farm, El-Behera Governorate-Egypt

Heavy metals are the most harmful contaminants which affect people health. The research objective of the present study was to determine the levels of cadmium (Cd), lead (Pb), chromium (Cr), copper (Cu) and zinc (Zn) in grey mullet fish collected from Barseque fish farm (Behera Governorate, Egypt). Moreover, heavy metals were determined in irrigation and Barseque farm water. Quality Index Method (QIM) scores showed good freshness condition of collected fresh fish. Variations in chemical composition of grey mullet fish collected from fish farm during winter and summer were noticed. Moisture content highly significant decreased in summer than in winter while fat increased in summer than in winter. Electric conductivity significantly increased in irrigation and farm water in summer, while there was no difference in pH. The results of heavy metals showed that the levels of Cd, Pb, Cr, Cu and Zn in different fish organs(liver, gills and muscles) were significantly higher in summer than winter, it was in the increasing order of liver>gills> muscles. Cadmium and lead concentrations in irrigation water and farm water that detected during winter and summer season were higher than the maximum permissible limit according to WHO/FAO and Egyptian Ministry of Water Resources and irrigation, law 48/1982.Cadmium, copper, lead and chromium concentrations in irrigation water and farm water showed no significant difference between winter and summer but zinc were significantly higher in summer than winter. Heavy metal concentrations that measured during winter and summer seasons in grey mullet fish organs were lower than the minimum acceptable daily intake recommended by WHO. Generally, the values of metals in the fish muscles were accepted by the international legislation limits and are safe for human consumption. On the other hand, it was strongly recommended not to eat head with gills or livers of fish. Conclusively, a regular monitoring program of heavy metal is recommended for protecting these organisms, and to reduce the environmental risks.