Irrigation Frequency Research Articles

Multi-objective optimization of rice irrigation modes using ACOP-Rice model and historical meteorological data

Current rice production in China is associated with low rainfall use efficiency. In order to increase rainfall use efficiency and develop simple water-saving irrigation modes that could be readily implemented by farmers, a new multi-objective optimization framework for irrigation modes of paddy rice was developed, based on a modified version of the AquaCrop model called ACOP-Rice model. The optimization focused on the water level at which irrigation was triggered for five growth periods and the irrigation frequency, rainfall use efficiency and yield were optimized. The procedure was tested on nine rice production cases in China for which over 60 years of historical meteorological data and irrigation guidelines were available. Analysis of the weather data showed that rainfall distribution varied greatly between the different locations and growth periods. The results obtained by following the current guidelines were compared to three optimal solutions that corresponded to minimum number of irrigation events, maximum rainfall use efficiency and “balanced” performance in which equal attention was given to rainfall use efficiency and irrigation frequency, respectively. Overall, the optimization led to lowering the water depth at which irrigation was triggered. The optimal water level after irrigation varied between the different cases, depending on the combined effects of rainfall distribution, operation constraints and length of growth period. Compared to the current guidelines, the optimized irrigation modes reduced the proportion of drainage caused by rainfall after irrigation. For optimal solutions with minimum number of irrigation events, maximum rainfall use efficiency and “balanced” performance, the number of irrigation events was reduced by 57 %, 18 % and 44 % on average (9.4, 3.0 and 7.4 fewer irrigation events per year) while on average rainfall use efficiency improved by 5 %, 19 % and 17 % without significant yield loss.

Effect of the Irrigation Interval and Nitrogen Rate on Yield and Yield Components of Onion (Allium cepa L.) at Arba Minch, Southern Ethiopia

Onion (Allium cepa L.) is an important cash crop for smallholder farmers in the Central Rift Valley of Ethiopia. However, its productivity is low, owing to a number of factors including inappropriate irrigation water and nitrogen management. A field experiment was, therefore, conducted at Amibara farm, Arba Minch, Ethiopia, during the 2018/19 dry season to determine the effect of the irrigation interval and nitrogen rate on growth, yield, and yield components of onion (Bombay Red variety). The treatments comprised four irrigation intervals (3, 6, 9, and 12 days of crop water requirement, ETc) and four nitrogen levels (0, 50, 100, and 150 kg·N·ha−1). The experiment was laid out in a split-plot design using irrigation intervals as main plots and nitrogen rates as subplots with three replications. The growth parameters, yield components, and final yield of onion were significantly higher with 3 and 6 days irrigation intervals (which were statistically similar) than 9 and 12 days irrigation intervals. The increasing N rate significantly increased the growth and yield components up to 150 kg·N·ha−1, but the response was significant only up to 100 kg·N·ha−1 on the final yield of the crop. The growth and yield contributing parameters, showing enhancement with frequent irrigation and higher N rates, had a significant bearing on the final yield of onion. The irrigation at 6 days interval combined with 100 kg·N·ha−1 gave a higher marketable yield (30.21 t·ha−1), net return (Birr 288,458 ha−1), and marginal rate of return (8586%). As such, irrigation at an interval of 6 days and fertilizer N at the rate of 100·kg·ha−1 may be recommended for higher productivity and profitability of onion at Arba Minch, Gamo Zone, southern Ethiopia.

IrriMap_CN: Annual irrigation maps across China in 2000–2019 based on satellite observations, environmental variables, and machine learning

Agricultural irrigation, as an important practice to protect crops from drought and promote grain yield, has a long history in China. A timely and precise dataset about the extent and dynamics of irrigated areas is necessary for water allocation and agricultural management but is scarce in China. Here we developed annual irrigated cropland maps across China (IrriMap_CN) at 500-m resolution from 2000 to 2019, using MODIS data, machine-learning method, and Google Earth Engine platform. First, we generated annual nationwide training samples by strictly screening the existing irrigation maps downscaled from the statistical data. Second, we implemented locally adaptive random forest classifiers in 511 nominal 1° × 1° grid cells across China with MODIS vegetation indices, climatic factors, and topography variables. Third, we conducted nationwide pixel-wise validation of the IrriMap_CN using independent samples. The validation results based on more than 3000 ground truth points revealed that IrriMap_CN had high accuracies ranging from 77.2% to 85.9%. The time series of IrriMap_CN detected substantial expansion of irrigated areas in Xinjiang and Heilongjiang (more than 50% in total) and pronounced decreases in Sichuan, Jiangsu, and Hebei. The analyses of irrigation frequency, start time, and end time implied that North China Plain was the most intensive irrigated area; but the irrigation area showed a decreasing trend since 2000, consistent with the reduced agricultural water consumption. The annual irrigation datasets allow us to understand the spatiotemporal dynamics of irrigated croplands in China and are expected to contribute to the improvement of earth system models and facilitate sustainable agricultural water management.

Study on spatio‐temporal variation mechanism of phytic acid contents of wheat grains

SummaryThis study aimed to understand the spatio‐temporal variation mechanism of phytic acid in wheat. Firstly, phytic acid contents of wheat from the main producing areas in China were investigated. Then in combination with statistical methods, the effects of the geographical origin, variety, harvest year, their interactions as well as different irrigation frequency on phytic acid contents of wheat were comprehensively analysed based on field experiments. Furthermore, the structure of phytic acid in wheat was analysed by Fourier transform infrared spectroscopy. The phytic acid contents of wheat in China ranged from 6.262 to 9.872 g kg−1. All the factors had significant effects on phytic acid contents of wheat. The characteristic spectra related to phytic acid in wheat included 3348, 1156, 1081, 1019, 927 and 861 cm−1. The variety had the greatest impact on phytic acid contents of wheat. This study could provide reference for breeding wheat with low phytic acid contents.

Irrigation Scheduling and Weed Management: A Sustainable Approach for Managing Broomrape and Other Weeds in Tomato Crop

Broomrape (Orobanche cernua L.) is an obligate root parasitic weed that significantly reduces the qualitative and yield attributes of tomatoes globally. The efficient management of broomrape is challenging because of its complicated parasitic nature. Field trials were conducted to assess the influence of various irrigation scheduling and weed control strategies on broomrape, weed presence, and tomato productivity. The experiment was conducted with a randomized complete block design (RCBD) with a split-plot arrangement and was replicated three times. Three irrigation intervals (3, 6, and 9 days) were assigned to the main block, while sub-blocks including treatments and year were taken as the source of variance (year × irrigation timing × treatments). The experiment comprised sixteen treatments, including transparent polythene, black polythene, weedy check (Control), sole weeding of broomrape only, weeding of all weeds, weeding except broomrape, humic acid 25 kg ha−1+ copper oxychloride in single and split doses, copper oxychloride (1.5 kg a.i ha−1 in single and split doses), ammonium sulphate 200 kg ha−1 in single and split doses, copper sulfate (2 kg ha−1 in single/split doses), and glyphosate 48 SL (1.5 kg a.i ha−1) and pendimethalin 33 EC (1.44 kg a.i ha−1). The results revealed that among the various irrigation intervals, the highest broomrape intensity (4.34 plant−1) was observed with a9-day irrigation interval. Similarly, the highest weed density (35 m−2) resulted in a3-day irrigation interval. Furthermore, irrigation at a 6-day interval increased the plant height by 11%, fruit yield tons ha−1 by 24.9 %, and produced the highest cost/benefit ratio (CBR) of (1:4). Black polythene, transparent polythene, and pendimethalin reduced the weed density by 92%, 89%, and 84%;weed dry biomass by 97%, 95%, and 91%; and broomrape intensity by 67%, 77%, and 28%. Conversely, the plant height increased by 24%, 23%, and 23.6%; and fruit yield by 286%, 270%, and 191%; and had the highest CBR of 1:5, 1:4, and 1:4, respectively, as compared to the weedy check. Consequently, an increase in irrigation frequency increases other weed densities and decreases the broomrape intensity plant−1 of tomato. Therefore, black polythene could be recommended in a severely broomrape-infested field. Moreover, irrigation at 6-day intervals combined with pendimethalin and ammonium sulfate fertilizers revealed the lowest incidence of broomrape and other weeds and produced an economic yield.

Nitrogen Rate, Irrigation Frequency and Volume Differentially Influence Growth, Flowering, and Nutrient Uptake of Container-Grown Rhododendron during the Following Growing Season

Sustainable nutrient and water management are critical for optimizing the quality and subsequent landscape performance of nursery plants. In this 2-year study, we investigated the influence of different nitrogen (N) rates [N-free fertilizer (0 N) or N-free fertilizer plus 7 (0.5 N) or 14 (1.0 N) mg N per day from NH4NO3] and irrigation frequencies and volumes [once daily to 50% or 100% container capacity (CC) or twice daily with the same total amount of water as 100% CC] on plant growth, flowering, and nutrient uptake of three rhododendron cultivars, including one deciduous cultivar, Rhododendron ‘Gibraltar’ and two evergreen cultivar, Rhododendron ‘P.J.M.’ and Rhododendron ‘Catawbiense Album’. In each case, the plants were grown in soilless media in year 1 and transplanted to soil in year 2. Increasing the N rate in year 1 increased plant biomass and N content in both years and improved flowering performance the following year. Furthermore, in year 1, irrigation once daily to 50% CC or twice daily to 100% CC enhanced the uptake of several nutrients in each cultivar and the growth of the evergreen cultivars. Plants that were irrigated more frequently during year 1 performed better in the landscape the following year, while those irrigated to 50% CC only performed better in the deciduous cultivar. In the evergreen cultivars, lower irrigation volume altered nursery plant qualities, resulting in a trade-off between flower production and growth in year 2. Our results indicate that manipulating N rates and irrigation frequency and volume can be used to alter nursery stock qualities and improve subsequent performance in the landscape.

The effect of water and nitrogen on drip tape irrigated silage maize grown under arid conditions: Experimental and simulations

Nutrients and nitrate move to the boundary of the wetted zone under drip-tape irrigation (DTI) of row crops, so irrigation depth, wetted width, and irrigation frequency are the most important factors in managing the wetting front and keeping N in the root zone. Many farmers in arid regions who have changed their irrigation systems to DTI, but they are still applying N in two splits as they are used for surface and sprinkler irrigation. Crop models can be used to optimize the timing and amount of nitrogen fertilizer applied to minimize both N leaching and the amount of N remaining in the soil after harvest. The objectives of this study were to calibrate the Cropping System Model (CSM)-CERES-Maize for two maize hybrids and to evaluate the model under DTI with two different soil wetting widths. The single cross Hybrid 704 (SC704) grown in two experimental fields (Exp-1 and Exp-2) and the single cross Hybrid 606 (SC606) grown in one experimental field and two farmer fields (Exp-3, Ff-1 and Ff-2) were evaluated during three years (2016, 2017 and 2019). Plant traits including leaf area index (LAI), total biomass (TB), soil moisture (SM), nitrogen uptake (NU) and water productivity (WP) were measured. Soil NO3-N was measured at three distances from the planting row and three soil depths in Exp-1 and Exp-3 during two maize growth stages. The fraction of the wetted width (fw) along drip-tape was 70% in Exp-1% and 100% in Exp-3 (referred to as fw-70 and fw-100, respectively). The results showed good performance of the model for simulating TB and LAI with NRMSE < 21.9% for the two hybrids in the applied N fertilizer treatments. The accuracy of the simulation of SM and WP in fw-100 was better than that of fw-70. Simulated NO3-N followed the observed trend for fw-100, while model performance varied for the different irrigation and N levels in fw-70. Model accuracy for soil NO3-N prediction decreased for the high N fertilizer application under deficit irrigation management. These differences were related to the wetting pattern volume, the distribution of N in the soil profile, and accumulation of soil N under DTI. Overall, the model can simulate TB and NU with high accuracy, SM with good accuracy, and soil NO3-N with an acceptable accuracy under DTI. The accuracy of the model was also higher for the unlimited wetting width, as compared to the limited one. This study showed that the CSM-CERES-Maize model can be used for evaluation of nitrogen management practices for drip irrigated maize grown under arid conditions.

A field survey suggests changes in oasis characteristics in the Kebili region of southern Tunisia

Since their establishment, “traditional” oases have been known to be three-layered, while modern oaseshave been organized from their outset with one layer only of ‘Deglet Nour’ date palm cultivars. However, these definitions may no longer apply for Kebilian oases. A survey was therefore carried out on a random sample of 52 plots in Kebilian oases (“traditional” n=26 and “modern” n=26) to investigate the current situation. The data collected were analysed by the Pivot Tables method and a Chi-2 test of independence, and by a Multiple Component Analysis completed by an Ascending Hierarchical Classification analysis to characterise and classify each oasis type. Our results showed that “modern” oases have greater crop diversity than expected and can be organized in two or three-layer oases. In contrast, high crop diversity and the three vertical layers were found to be less frequent than expected in “traditional” oases. Our investigation found water availability in the oases, and irrigation frequency, to be the key factors of Kebilian oasis layout and typology changes. Agro-biodiversity losses could jeopardize the sustainability of the oasis system in “traditional” oases.

Effects of mulches combination with different SWC on soil properties and soybean production

The use of water and nutrient balance in soil for the soybean establishment in farms needs to be the topmost priority without increasing the cost of production is needed in this high soybean consumption country, Japan. The objective of this study is to observe the five levels of water stress intensity on plant growth, yield, irrigation frequency, and soil chemical properties changes with the help of two biodegradable mulches was a goal in this sustainable soybean crop production. An experiment designed with two mulch types, shredded paper (SP) and living mulch clover (CL) with 5 SWC (Soil Water Contents) treatments were monitored for irrigation. Total N increased from the original soil N of 3.05 mg/g to 3.53-4.05 mg/g after harvest particularly under CL at medium SWC-2,3,4 levels (35% -15%). Lower SWC level affected more in CL mulched soybean for competition with nutrient and water resource utilization which led to lower soybean yield and earlier harvest. On the other hand, applying SP mulches benefit soybean yield but the total C/N return to soil results in microbial immobilization. To conclude, the soybean seed yield was highest at SWC level 5 for both mulches and clover plants’ best establishment in the SWC-3 level.

Adaptation of Salvia fruticosa, S. officinalis, S. ringens and interspecific hybrids in an extensive green roof under two irrigation frequencies

With the ultimate goal of introducing new species of sage to the green roof industry, the adaptation of the Mediterranean sage species Salvia fruticosa, S. officinalis, S. ringens and the interspecific hybrids S. fruticosa × S. ringens and S. officinalis × S. ringens was investigated, under normal and sparse irrigation in an extensive green roof in Athens, Greece. Rooted cuttings were planted (April 2021) on shallow (10 cm) substrate (grape-marc compost: perlite: pumice, 3:3:4, v/v) and irrigated when substrate moisture was 16-22% (normal irrigation) or 7-11% (sparse irrigation). All sage types established satisfactorily on the green roof, even under sparse irrigation, except S. fruticosa, which had the highest vegetative growth and at the end of the experiment (September 2021) showed the highest mortality rate regardless of irrigation frequency. Similar to the S. fruticosa response showed the S. fruticosa × S. ringens hybrid under normal irrigation. Both hybrids, S. fruticosa × S. ringens and S. officinalis × S. ringens had a lower mortality rate under sparse irrigation compared to the parental species. S. officinalis × S. ringens formed more lateral shoots than its parental species and had an almost spherical compact canopy, which is a nice feature for an ornamental plant. S. officinalis and S. ringens developed bigger horizontal diameter, which is valued for rapid substrate coverage in a green roof installation. All sage types flowered except S. fruticosa. All sage types showed higher values of stomatal resistance under sparse irrigation, while ΦPSIIo values under both irrigation frequencies indicated normal operation of the photosynthetic apparatus. S. officinalis, S. ringens and S. officinalis × S. ringens hybrid are highly recommended for sustainable extensive green roofs in arid/semi-arid regions.

Growth and Yield Evaluation of Avocado (Persea americana) Varieties in Lowland Agro Ecology of Raya Azebo, Southern Zone of Tigray Region, Northern Ethiopia

Avocado is among the subtropical fruit crops produced in Ethiopia; however, the production and Productivity of avocado is influenced by different factors; of which lack of improved and well adapted varieties are the major one. So, an experiment was conducted at Fachagama from 2013 to 2019 to evaluate and select the best adaptable avocado variety/ies at Raya Valley. Six avocado varieties namely Ettinger, Fuerte, Pinkarton, Hass, Naba and Bacon were laid in RCBD and replicated three times. To achieve the objective, the growth, phenological and yield data were collected and analyzed using SAS software. Accordingly, above graft union stem girth diameter was significantly (P≤0.01) affected by variety, while tree height and canopy diameter were not significantly ascertained by variety. All the tested avocado fruit yield parameters were significantly (P≤0.01) influenced by variety throughout the three years except marketable fruit yield tree-1 and the total yield tree-1 which was not significantly (P≥0.5) determined by variety during 2017 fruit harvesting year. Variety exerted significant (P≤0.01) variation on fruit length (cm) fruit weight (g) and seed weight respectively, throughout the three years (2016-2018), the two years (2017 and 2018) and the two years (2016 and2018). The highest girth diameter (61.44mm) was obtained on Nabal variety. Likewise, the highest (15.51 and18.88kg tree-1) total yield was recorded in Pikerton and Bacon varieties respectively during 2016 and 2018 respectively. From the result Pinkerton and Bacon are recommended for Raya Valley and other areas having similar agro-ecologies. However, it is important to consider the water requirements in terms of irrigation depth and frequency of avocado.

Soil moisture distribution pattern of surface drip irrigated mango

At present, Pakistan has been facing acute shortage of irrigation water and farmers have been using conventional irrigation methods for orchards, such as flood and basin irrigation, thus wasting huge amount of fresh water. Therefore, it is necessary to find efficient irrigation methods to cope with this major burning issue. The micro drip irrigation method is considered efficient but in the case of mango orchards there is a problem of irrigation frequency, number of emitters, and duration of flow from emitters to meet water demand. Considering the above, an experiment was conducted in the experimental field of the Sindh Agriculture University, Tandojam, by installing the drip system with two circular peripheries of lateral lines in clay loam soil covering the entire canopy of a mature mango tree. The radius of the first and second periphery around the tree trunk was 100 cm and 150 cm, respectively. Four emitters with 4 dm3∙h –1 discharge of individual dipper were fixed in each periphery. Emitters were tested for six different irrigation times, i.e. 1, 2, 3, 4, 5 and 6 h, to observe the moisture distribution pattern. Hydraulic characteristics, such as density, field capacity, porosity, infiltration rate, available water and permanent wilting point (PWP), were determined using standard methods (1.4 g∙cm –3, 33%, 49%, 8 mm∙h –1, 12.41% and 20% respectively). The texture class of the soil profile was determined as clay loam at the soil depth 0–120 cm. Fifty soil samples were collected at 0–10, 10– 30, 30–60, 60–90, and 90–120 cm depths and at 0–20, 20–40, 40–60, 60–80 and 80–100 cm distances on two opposite sides of emitters. The emitters provided sufficient moisture up to field capacity in clay loam soil with flow duration of 4 h. The maximum moisture distribution efficiency was 77.89% with flow duration of 4 h at vertical depth of 0–120 cm and 0–100 cm distance horizontally among four emitters as compared to 1, 2, 3 h flow duration which under irrigated the canopy area and 5, 6 h flow duration which excessively irrigated the canopy area of the mango tree. The water demand of the mango tree was met by 4 h flow duration which provided adequate moisture to the entire canopy up to 120 cm depth in the root zone and water saving was calculated as 15.91% under the installed drip irrigation system as compared with the conventional (basin) irrigation method.

Prospects of Hydrogels in Agriculture for Enhancing Crop and Water Productivity under Water Deficit Condition

In arid and semiarid regions and under rainfed conditions, water availability is one of the principal ecological constraints that hinder agriculture’s sustainability. The super absorbent polymer (agricultural) is water-absorbing and is cross-linked to absorb aqueous solutions through bonding with water molecules. It is a new approach to water management under water-stressed conditions to conserve soil moisture in the active rooting zone of crops by reducing the evaporation, deep percolation, and runoff losses. Agricultural hydrogels are water retention granules which swell their original size to numerous intervals when they come in contact with water. It can absorb and retain a huge amount of moisture under plentiful rainfall and irrigation events and release it back to the soil for mitigating crop water demand when the rhizosphere zone dries up under drought conditions. It plays multifarious roles in agriculture including soil-water retainer, nutrient and pesticide carriers, seed coating, soil erosion reducer, and food additives. It has the extraordinary ability in improving different physicochemical, hydrophysical, and biological properties of soil, simultaneously decreasing irrigation frequency, enhancing the water and nutrient use efficiencies, and increasing the yield and quality of the field, plantation, ornamental, and vegetable crops. These biodegradable materials are nontoxic to the soil, crop, and environment. Hence, the addition of the hydrogel polymer will be a promising and feasible technological tool for augmenting crop productivity under moisture stressed conditions.

Can perceptions of reduction in physical water availability affect irrigation behaviour? Evidence from Jordan

ABSTRACT Frequent droughts and rapidly depleting groundwater reserves have deepened the water scarcity crisis in Jordan. Even though most farms use ‘water-saving' technologies, groundwater depletion continues at an alarming rate. We investigate how farmers' past experiences of physical water availability are related to their current behaviour, by examining the frequency of irrigation and how farmers determine irrigation needs. Data came from a primary survey of 414 commercial farms. Using the seemingly unrelated regression estimator, we find that respondents who perceived a reduction in physical water availability and agricultural losses in the past irrigated more frequently and were more likely to use self-judgement in determining irrigation needs. These relationships were more pronounced for smaller farms than larger farms, farms with sandy soil, mono-cropping farms, and owner-managed farms. These effects were lower for farms that preferred in-person approaches for receiving irrigation advice. While the frequency of irrigation was higher among stone fruit farms, the probability of using self-judgement in determining irrigation needs was higher in olive farms and vegetable farms. We argue that farmers' irrigation behaviour must be considered for groundwater management policy and planning in Jordan, an important component of the country’s ability to adapt to climate change.

Is Greenhouse Rainwater Harvesting Enough to Satisfy the Water Demand of Indoor Crops? Application to the Bolivian Altiplano

As many other regions worldwide, the Bolivian Altiplano has to cope with water scarcity during dry periods, which in turn impacts on crop production as flood irrigation is overwhelmingly extended in the region. Since farming is the main income in the Altiplano for most families, the availability of greenhouses with water harvesting systems may represent a solution to warrant all year round production and food access. We study the daily satisfied water demand from a balance between rainfall collected by a greenhouse roof and water used for indoor crop irrigation assuming a tank is available for water storage. This balance is analyzed for 25 greenhouses spread over Batallas Municipality, close to Titicaca Lake, Bolivia, and for two case studies: (i) using irrigation data collected from farmers in the frame of a regional project; (ii) using theoretical daily water requirements assuming an intense greenhouse farming. Our evaluation includes a sensitivity analysis of relevant parameters, such as the influence of the time window of rainfall used in the simulation, the runoff coefficient, the roof surface area, the irrigation drip system, the irrigation frequency, the crop coefficient, the volume of water used for crop irrigation, and the capacity of the water tank. Overall, we find that the runoff coefficient has little impact on the satisfied demand rate, while all other parameters can play an important role depending on the greenhouse considered. Some greenhouses are able to irrigate crops normally during the wet season, while during the dry season, greenhouses are not able to satisfy more than 50% of the theoretical water requirements, even when large tanks are considered. Based on these results, we recommend the construction of greenhouses with a ground surface of &lt;50 m2 attached to the largest available covered water tank. The information here provided can be used by stakeholders to decide their policies of investment in infrastructures in the Altiplano. Finally, the approach we follow can be applied to any other region where rainfall, temperature, and greenhouse data are available.

Plastic-shed vegetable cultivation alters soil gross nitrogen transformation rates and nitrous oxide production pathways

Plastic-shed vegetable cultivation is characterized by high nitrogen (N) application rates, frequent irrigation and multiple cropping, probably leading to different soil N transformation rates compared to open-field cultivation. However, how continuous cultivation of vegetables under plastic sheds affects soil N transformation rates and associated nitrous oxide (N2O) emissions remains unclear. Here, a 15N-tracing experiment in combination with the qPCR technique was used to investigate the effects of conversion from conventional open-field cultivation to plastic-shed vegetable cultivation, as well as the age of this shift, on soil gross N transformation rates, N2O emission pathways and associated microbial abundances. Five typical fields, including a wheat–maize rotation system field and four adjacent plastic-shed vegetable fields under cultivation for 2, 5, 12 and 20 years, were selected. Soil gross N mineralization rates increased significantly after two years after conversion from a wheat–maize rotation system to a plastic-shed vegetable system, and then decreased with an increase in plantation age, which could be attributed to decreased soil total phosphorus availability. Long-term vegetable plantation under plastic-shed decreased soil gross autotrophic nitrification rates significantly by decreasing ammonia-oxidizing bacteria abundance probably due to decreasing soil pH. Such decreased rates of autotrophic nitrification further led to decreased N2O emissions under plastic-shed cultivation. Under long-term plastic-shed cultivation (>2 years), negligible gross nitrate-N (NO3−-N) immobilization rates were observed due to the preferential use of ammonium-N by soil microbes, which was probably responsible for rapid NO3−-N accumulation in soils. Overall, these results could be of help to elucidate the mechanisms of soil N2O emission and NO3−-N accumulation in plastic-shed vegetable fields.

Irrigation Frequency and Volume has Little Influence on Phytophthora Root Rot in Container-grown Rhododendron

Abstract We evaluated whether reducing irrigation frequency and volume alters the ability of Phytophthora plurivora and P. cinnamomi to cause root rot on rhododendron grown in a noninfested potting medium or media infested with 1 or 100 propagules per gram (ppg) of pathogen. Plants were irrigated to maintain a substrate moisture of &amp;gt;70% container capacity (1.0X), one-half volume of 1.0X (0.5X), or two times the volume of 1.0X at each irrigation event for one week, followed by no irrigation, until soil moisture reached &amp;lt;50% container capacity. Aboveground disease symptoms (chlorosis, stomatal conductance, wilting, and plant death) were evaluated weekly and root rot, pathogen presence, plant biomass, and nutrient uptake were measured at the end of each trial. Both pathogens generally caused mild disease at 1 ppg and severe disease at 100 ppg. Reducing irrigation did little to lessen disease caused by either pathogen once infection had occurred. Instead, severe root infection often led to increased soil moisture and root rot across all irrigation treatments as roots became progressively compromised in their ability to take up water. Results show that reducing irrigation after infection has occurred is unlikely to effectively control root rot. Species used in this study: Phytophthora species (Phytophthora cinnamomi Rands; Phytophthora plurivora T. Jung and T.I. Burgess); rhododendron, Rhododendron catawbiense Michx. ‘Album', ‘Roseum Elegans', and ‘Roseum Pink'.

Effects of St. Augustinegrass genotype and irrigation frequency on turfgrass quality in a subtropical environment

AbstractGrowing urban populations have placed greater demands on municipal water supplies, especially during dry periods. Efforts are underway to develop turfgrasses with better performance using less irrigation. The objective of this research was to assess the effects of irrigation management and St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze] genotype on turf quality (TQ). The field study conducted in Citra, FL, was a split‐plot design with the main plot (irrigation) arranged in blocks. Calendar‐based irrigation treatments were soil sensor‐based, 8X, 4X, 2X, and 1X per month (MO) and none. St. Augustinegrass genotypes included three commercial cultivars and eight experimental entries. Turfgrass quality varied with time, genotype, and irrigation. Sensor‐based and 8XMO irrigation produced the highest TQ values, ranging from 5 to 7 for all cultivars, but sensor‐based irrigation used less water overall. Turf quality declined with 2XMO and more restrictive irrigation frequencies, with TQ values ranging from 2 to 4. Several recently developed breeding lines performed better across all the irrigation treatments than current commercial cultivars. To satisfy both municipal watering restrictions and turfgrass health requirements, sensor‐based irrigation coupled with the use of improved breeding lines and cultivars such as DALSA 1618 or FSA1602 (CitraBlue®) offer the potential to maintain quality turfgrass while substantially reducing residential irrigation use.

Effects of Soil Water Regulation on the Cotton Yield, Fiber Quality and Soil Salt Accumulation under Mulched Drip Irrigation in Southern Xinjiang, China

To optimize suitable water-saving and soil salt-controlling irrigation needed for the high yield and good quality of cotton in southern Xinjiang, a field experiment was carried out to study the effects of soil water lower limits on water consumption, water use efficiency (WUE), yield, cotton fiber quality and soil salt accumulation under mulched drip irrigation in Korla, Xinjiang. The field capacity (FC) was regarded as the upper limit of soil moisture, and five soil water lower limits (85% FC, 75% FC, 65% FC, 55% FC, 45% FC, referred as T1~T5, respectively) were designed during the cotton growth period. The results indicated that the irrigation frequency and irrigation quota of cotton were gradually increased with the increase in the soil water lower limit, while the water consumption modulus for T2 treatment during the critical period of water demand arrived at the maximum value. Moreover, with the decrease in the soil water lower limit, the WUE, fiber micronaire value and fiber maturity index of cotton increased, whereas the yield, nitrogen partial factor productivity (PFPN) and fiber breaking elongation of cotton decreased. However, when the soil water lower limit exceeded 75% FC, the increase had little effect on the cotton yield increase and PFPN improvement, and the yield and PFPN for T2 treatment were 7146.4 kg∙hm−2 and 23.82 kg∙kg−1, respectively, In addition, the decrease in the soil water lower limit was unfavorable for an increase in fiber length, but it was conducive to the enhancement of fiber strength. Furthermore, soil salt accumulated inside and outside the film for the designed soil water lower limits, and the amount of accumulated salt in 0~100 cm followed T3 &gt; T5 &gt; T1 &gt; T2 &gt; T4. Based on a comprehensive analysis with the entropy TOPSIS method, the findings of the present study suggested that the suitable soil water lower limit for cotton under mulched drip irrigation was 75% FC in southern Xinjiang, China.

Uptake of Cu, Hg, and As in wild vegetation, associated to surface water in the Copiapó valley, before the 2015 alluvium.

In an annual monitoring in the Copiapó valley, the concentration of Cu, Hg, and As in sediments was related to environmental transfer processes, these elements also being present in surface water. The goal was to evaluate the uptake of the mentioned elements in wild plants of the Copiapó Valley, to determine if these species could be indicator plants to prevent environmental risks in local agriculture. From the same monitoring, the uptake of the elements was determined in wild plants growing near the irrigation channels; canopy of Tessaria absinthioides, Equisetum giganteum, Arundo donax, Melilotus indicus, Cortaderia rudiscula, and Sarcocornia neei was analyzed for the same elements. These plants were able to uptake Cu, Hg and As in concentration between 19 and 4674.5 times the environmental limits allowed for edible plants. This result shows that crop plants can also capture contaminants elements due to the frequency of irrigation. These plants can be used as indicators for the diagnosis of capture of the pollutants elements by plants and to prevent environmental hazards to human health in agricultural products from the Copiapó valley.