Moderate Irrigation Research Articles

Planting models and deficit irrigation strategies to improve radiation use efficiency, dry matter translocation and winter wheat productivity under semi-arid regions

The dry-land farming system of China relies on plastic film mulching and natural rainfall to mitigate damage caused by drought. However, the applications of deficit irrigation modes combined with the planting models can significantly increase production of wheat, dry matter translocation and radiation use efficiency (RUE) remains unidentified. Thus, in 2016–2018, we conducted field trials that implemented four deficit irrigation modes (IJF: irrigation at jointing and flowering stages; IF: irrigation at flowering stage; IJ: irrigation at jointing stage; NI: no irrigation) under two cultivation patterns (ridge furrow rainfall harvesting system (RF); traditional flat cultivation (TF)). The results indicated that the effects of RF system with deficit irrigation (IJF: 250 mm) could significantly increase the soil moisture, and thus enhanced LAI, In value, IPAR, RUE, and PAR capture ratio than that of TF-NI planting. This is due to decreased canopy light transmittance (LT), reflection and penetration ratio of PAR, as a result considerable improve the biomass translocation and grain yield. Owing to the very low soil water content after the seed-filling, the LAI, IPAR, and In value decreased during the seed-filling under water stress, ultimately affecting the dry matter translocation efficiency. While the IJF and IF treatments provided water for reproductive growth stage, therefore, the production of wheat and RUE were significantly maximum compared with IJ and NI irrigation mode. Under the RF system with IJF, IF, and IJ treatments the grain yield increased by 81.2%, 56.8%, 45.6% and 17.2%, then that of TF-NI treatment, respectively. The highest RUE (1.93 g MJ−1), dry-matter translocation (154.2%) and seed yield (81.2%) were obtained in the RF-IJF treatment compared with TF-NI. Therefore, the RF-IJF treatment significantly improved the earlier development and rapid plant growth, which is a suitable planting model for increasing soil moisture, LAI, RUE, DMT, and winter wheat production.

Effect of Aeration on Blockage Regularity and Microbial Diversity of Blockage Substance in Drip Irrigation Emitter

Aerated drip irrigation is rendered as a new water-saving irrigation method based on drip irrigation technology, which is endowed with the function of effectively alleviating the problem of rhizosphere hypoxia in crop soil, enhancing the utilization rate of water and fertilizer; as a result, it improves the harvest and quality of crops. However, clogged emitters are important indexes, among others, that pose an influence to the service effect and life duration of drip irrigation systems. At present, the working principle and mechanism of the influence of air feeding on the blockage of drip irrigation emitters remain unclear. Therefore, based on the two gas filling methods of the micro/nano bubble generator and Venturi injector, the dynamic change process for the average flow ratio of an air-filled drip irrigation emitter was studied by the method of emitter plugging test. 16S rRNA sequencing was used to analyze the microbial diversity of the emitter plugs. The results show that the air injection can pose influence on the clogging procedure of drip irrigation emitters, and more importantly, it makes the distribution of blocked emitters more uniform, thus improving the uniformity of the system. Different filling methods have different effects on the blockage of the emitter. Among them, the blockage time of drip irrigation system under the micro/nano aerated drip irrigation (MAI) mode is 5.73 times longer than that under unaerated drip irrigation (UVI), and similarly, Venturi gas drip irrigation (VAI) is close to that under UVI. The filling method changed the microbial diversity of the blockage in the emitter. Among them, the number of operational taxonomic unit (OTU) unique to MAI was 2.1 times that of UVI, and the number of OTU unique to VAI was 1.3 times that of UVI. Meanwhile, gas addition will inhibit the growth of Nitrospirae and Proteobacteria microbial communities and promote the growth of Firmicutes and Actinobacteria microbial communities. Furthermore, the increase in microbial extracellular polymer in the plugging material of the emitter was inhibited and the plugging process of the emitter was slowed down. The research results are of great significance in the disclosure of the clogging mechanism of drip irrigation emitter and constructing the green, anti-blockage technology of aerated drip irrigation.

Deficit irrigation decision-making of indigowoad root based on a model coupling fuzzy theory and grey relational analysis

Water scarcity is a critical constraint to the cultivation of medicinal crops. Establishing irrigation requirements for medicinal plants is crucial for the large-scale production of crude drugs in China. To evaluate the response of indigowoad root growth to water deficit (WD) under-mulched drip irrigation, and determine the optimal deficit irrigation mode for this medicinal crop in Hexi Corridor’s desert oasis, two WD levels were applied: mild (65–75% FC [field capacity]) and moderate (55–65% FC). These treatments were implemented during the vegetative growth (VG) and fleshy-root growth (RG) stages, and sufficient water supply maintained during the other plant stages. A total of seven combined treatments were imposed, with sufficient water supply (85–75% FC) as the control treatment. From the 2-year-long (2017, 2018) field experiment’s results, 12 indicators of indigowoad root growth, yield, water consumption and quality attributes were evaluated via weighted fuzzy evaluation and a grey relation-coupling model. Results indicated that, with greater irrigation amounts throughout the plant growth period, the fuzzy evaluation value of growth, yield and water consumption indicators increased whereas their quality indicators decreased. The fuzzy evaluation value of yield indicators of V1G0 (mild WD treatment during VG) was the highest (0.1582, 0.1581), while that of growth indicators was also relatively high (0.1524, 0.1532). Fuzzy evaluation values of growth and yield indicators of V1G1 (mild WD during VG and RG) exceeded those of V1G2 (mild WD during VG and moderate WD during RG), but evaluation value of quality indicators was lower for V1G1 (0.1457, 0.1457) than V1G2 (0.1494, 15155). Based on the weighted grey relation model, the comprehensive score of V1G0 was deemed best. Therefore, to ensure both yield and quality, the V1G1 is recommended. Our results can provide a scientific basis for efficient water-saving cultivation of indigowoad root in Hexi oasis regions.

Microbial community structure and function in paddy soil as affected by water-saving irrigation mode

The objective of this study was to understand how the water-saving irrigation mode affected the microbial community structure and function in paddy soil. A field experiment with three irrigation modes (flooding irrigation FI, alternate wetting and drying irrigation AI and ridge irrigation RI) was conducted, and DNA extracted from the upper 25 cm paddy soils were measured using whole genome sequencing (WGS). The results showed that FI, AI and RI modes were significantly distinct in microbial communities. Compared to FI mode, two water-saving irrigation modes (AI and RI) decreased the relative abundance of Euryarchaeota and showed significant difference in their microbial co-occurrence networks. Compared to FI mode, AI mode increased the relative abundance of Proteobacteria but decreased the relative abundance of Actinobacteria, while RI mode showed opposite effects. Some biomarker species associated with carbon/nitrogen metabolism, such as Cupriavidus taiwanensis, Gemmatirosa kalamazoonesis, Nitrospira moscoviensis, Pseudomonas tolaasii and Methanosarcina barkeri, were significantly sensitive to different irrigation modes. Meanwhile, two water-saving irrigation modes especially AI mode enhanced the genes involved in carbohydrate decomposition and nitrification pathways, while FI mode significantly enriched the genes involved in methane metabolism, denitrification and nitrogen fixation. Thus two water-saving irrigation modes decreased the main methanogen (Methanosarcina barkeri) and methanogenesis genes in paddy soil, while AI mode enhanced potentially beneficial microbes and carbon/nitrogen metabolic-related genes in paddy soil.

Bioenergetic efficiency of drip irrigation modes of grapes

In modern conditions of water scarcity, the research of the energy evaluation of different modes of drip irrigation to reduce the consumption of irrigation water, material and energy resources, their effective use on irrigated grape plantations cultivated on the sandy chernozems of the left bank of the Lower Dnieper, where only irrigation is the guarantee of annual, constant high yield of vineyards. The purpose of the research was to study the energy efficiency of grape drip irrigation regimes, determine the volume and structure of resource costs, and the level of their payback. Field and comparative-calculation methods were used during the research. The establishment and conduct of experiments were carried out according to the methodology of the research case. The paper presents the results of research on the energy efficiency of drip irrigation modes of grape plantations. It is established that maintaining an unhindered moisture supply to plants during the growing season is achieved by an additional cost of 9.29 GJ/ha of anthropogenic energy. A more economical regime of humidity of the active soil layer during the growing season reduces energy costs to 5.2-7.7 GJ/ha. The structure of additional energy costs, regardless of the irrigation regime of plantings, is dominated by the energy of irrigation water - 80% and energy carriers - 18 %. The practical significance of the research is to conduct an energy assessment of different modes of drip irrigation of grapes to reduce the consumption of irrigation water, material and energy resources and their efficient use

Assessment of greenhouse gases emissions, global warming potential and net ecosystem economic benefits from wheat field with reduced irrigation and nitrogen management in an arid region of China

In the context of global warming, water scarcity, and high fertilizer costs, identifying proper irrigation and nitrogen (N) management is essential for balancing emissions of greenhouse gases (GHGs), crop production, and economic benefits in arid regions. A two-year field study was conducted to determine the interactive effects of irrigation regimes (I100, 750 mm; I80, 600 mm and I60, 450 mm) and N application rates (N100, 300 kg ha−1; N75, 225 kg ha−1; and N50, 150 kg ha−1) on GHGs emissions, global warming potential (GWP), greenhouse gas intensity (GHGI), and net ecosystem economic benefits (NEEB) from spring wheat field in Northwest China. Our results depicted the lowest cumulative GHGs emissions and GWP with low irrigation and low N application rates but at the cost of a significant decrease in grain yield and NEEB compared to full irrigation and N application. Instead, moderate irrigation and N application (I80N75) showed the most promising effects by significantly reducing GHGs emissions while improving the NEEB and yield benefits. Compared to I100N100, the I80N75 treatment decreased cumulative N2O emissions by 43.2 % and 33.1 %, CO2 by 28.8 % and 26.2 %, GWP by 46.8 % and 35.6 %, and GHGI by 55.0 % and 43.5 % in 2015 and 2016, respectively. In addition, the I80N75 treatment improved the NEEB by 79.3 % and 78.6 % and grain yield by 15.2 % and 16.1 % in 2015 and 2016 compared to I100N100, respectively. The wheat field acted as a CH4 sink regardless of all the treatments. Soil moisture and inorganic N contents were the primary driving factors that influenced the GHGs emissions from the wheat field, manifested by their significant correlations. Overall, 600 mm irrigation and 225 kg N ha−1 fertilization is an effective strategy with a good trade-off between economic benefits and environmental performance from spring wheat fields in the arid region of Northwest China.

Алгоритмизация технологических режимов автоматизированной системы комбинированного орошения в теплицах с использованием электрохимически активированной воды

Irrigation is one of the main technological processes in greenhouse farming, which essentially provides qualitative and volumetric indicators of produced products. Thus, the combined irrigation technology which combines low-volume methods of drip and aerosol irrigation is widespread. We consider the combined irrigation system which includes an installation for water electro-chemical activation (ECA). Extended abilities of this system are caused by the reactivity of catholyte and anolyte, which are metastable products of water ECA. Catholyte and anolyte are used as growth stimulator and antiseptic respectively in the plant cultivation. Automation of the combined irrigation system, in addition to resource-saving, is also aimed to prevent technological modes violation due to the subjective (“human”) factor. Control algorithms for drip and aerosol irrigation with ordinary water, drip and aerosol irrigation with catholyte and aerosol irrigation with anolyte are described in the article. When the algorithm starts, the control testing is performed to detect possible failures in the irrigation system (for example, rupture of drip tubes or salting of drippers). In case of a detected issue, a diagnostic message is shown and accompanied by a sound signal. More complex technological irrigation modes associated with the use of catholyte and anolyte also include the performance monitoring of the water electrochemically activation unit. The control of the irrigation technological parameters (soil moisture, air humidity, soil pH) is carried out by retrieving the relevant sensors data and comparing the obtained values with the set ones. When the set points are reached the relevant technological links (electric pumps and electromagnetic valves) are switched off by the signal of the microcontroller. The presented algorithms are designed for developing the microcontroller control unit software for the combined irrigation system.

The eye wash technique: A simple and effective technique for intraoperative ocular surface lavage

Objectives: The author proposes an extremely effective and practical method of ocular surface hydrating and cleaning during anterior segment surgery, the Eye Wash Technique (EWT), in substitution for the traditional methods employing a syringe and cannula for ocular irrigation. Materials and Methods: The EWT utilizes the intraocular irrigating solution (IS) used in the surgery. It is performed by employing the irrigating line of the phacoemulsification (phaco) machine or the irrigating fluid IV drip in case of manual cataract surgery. The eye irrigation is performed directly from the Luer end attachment of these irrigating lines, which is positioned above the inner cantus pointing to the globe’s nasal limbal region. With the phaco machine pedal in position 1 (irrigation only) or in panel continuous irrigation mode in case of phaco surgery, or by opening the roller clamp of the IV drip line in case of manual surgery, IS flow ensues and is directed to the eye from a nasal direction to provide a steady flow to wash the exposed eye surface as well as the lid margins and lid speculum. The irrigation is maintained for two to five seconds with side-to-side jiggling if needed, to ensure complete ocular surface coverage. Cornea hydration is achieved and any unwanted material on the ocular surface is washed out. Results: The EWT was easily incorporated into the surgical routine with no difficulty in adaptation to the technique or in its employment. The surgical time was not prolonged when employing the technique. The EWT effectively provided both corneal hydration and ocular surface cleaning every time it was used, with no need to resort to the traditional syringe and cannula irrigation method at any time. Conclusion: The EWT should be incorporated into the anterior segment surgical routine and performed at the beginning of surgery, before inserting the intraocular lens, and at the end of the surgery; also, at any time during surgery should the need arise, enhancing anterior segment surgical visualization and safety.

Heat generation during implant site preparation and its effects on osseointegration: A review

Dental implants act as a bridge between the oral environment and deep core structures of the jaw. The temperature rise leading to heat generation in the course of operation of the dental implants results in thermal injury of the adjoining bone tissue to the implant site resulting into implant failure. Present review is focused on existing research done in the heat generation and its distribution during dental implant drilling. Various factors such as drill speed, drill design, mode of irrigation, depth of drill, drill diameter, drill material that affect osseointegration due to heat generated while drilling, are compared. The motive of this review is to assess the various factors that are responsible for heat generation and their effects on osseointegration during osteotomy. A systematic study reveals that the rise in the temperature at the implant site mainly depends upon the drill speed, drill diameter, depth of drill as well as irrigation used. The purpose of this review is taking these factors into consideration to find out the best possible parameters during implantation to avoid bone necrosis. The temperature during dental implantation ranges from 35 ℃ to 43 ℃ while in some in-vitro studies the temperature increases up to 50 ℃ was observed which is not admissible due to the thermally induced necrosis.

EFFECT OF NORMAL BENTONITE CLAY, MINERAL FERTILIZERS, AND IRRIGATION REGIME ON WINTER WHEAT

In addition to the norm N150P105K75 kg/ha of mineral fertilizers for winter wheat under conditions of typical gray soils of the Tashkent region, 3000 kg/ha of bentonite clay was applied for plowing, with soil moisture before irrigation during the growing season in the irrigation mode 60-70-60 and 70-80- 70% of the LFMC at the end of the growing season, the bulk density of the soil relative to the control variant decreased to 0,03-0,05 g/cm3 in the 0-30 cm. layer and to 0,07-0,11 g/cm3 in the 30-50 layer see, an increase in soil water permeability from 30 m3 to 100 m3/ha was noted. When irrigating under irrigation regimes of 60–70–60 and 70–80–70% of the LFMC and additional application of bentonite clay at a rate of 3000 kg/ha against the background of mineral fertilizers at a rate of N150P105K75 kg/ha, the increase in grain yield was 11,9–13,4 c/ha, and the level of profitability increased by 18,9–21,1% compared to the control.

Effect on Physiological Growth and Water Utilization of Rice under Different Varieties and Irrigation Modes

Effect on Physiological Growth and Water Utilization of Rice under Different Varieties and Irrigation Modes

Controlling the lodging risk of rice based on a plant height dynamic model

BackgroundRice is a key global food crop. Rice lodging causes a reduction in plant height and crop yield, and rice is prone to lodging in the late growth stage because of panicle initiation. We used two water irrigation modes and four fertilizer application intervals to investigate the relationship between lodging and various cultivation conditions over 2 years.ResultsPlant height data were collected and combined with aerial images, revealing that rice lodging was closely related to the nitrogen fertilizer content. The aerial images demonstrated that lodging mainly occurred in the fields treated with a high-nitrogen fertilizer, and analysis of variance revealed that plant height was signifi-cantly affected by nitrogen fertilizer. These results demonstrated that rice plant height in the booting stage was significantly positively correlated with the lodging results (r = 0.67) and nega-tively correlated with yield (r = − 0.46). If the rice plant height in the booting stage exceeded 70.7 cm and nitrogen fertilizer was continuously applied, according to the predicted growing curve of plant height, the plant would be at risk of lodging. Results showed more rainfall accumulated in the later stage of rice growth accompanied by strong instantaneous gusts, the risk of lodging in-creased.ConclusionThe results provide predictions that can be applied in intelligent production and lodging risk management, and they form the basis of cultivation management and response policies for each growth period.

Evaluation of the Effects of Water and Salinity Stress on the Growth and Biochemistry of Alfalfa (Medicago sativa L.) at the Branching Stage

The response of alfalfa to water and salinity stress differs during the whole growth period, and water stress has the most severe effects on the yield of alfalfa at the branching stage. However, the presence of soil salt can also enhance its drought resistance and alleviate the impact of water stress on yield. Thus, information on the responses of aboveground biomass, water-use efficiency and osmolytes to water and salinity stress at the branching stages of alfalfa development is urgently required. A pot experiment that combined three irrigation levels of 55–70% (W1), 70–85% (W2) and 85–100% (W3) of field capacity (FC) and four salinity levels was conducted in Dengkou County, Inner Mongolia, China, in 2018 and 2019. The percentage of mixed salt (NaCl:Na2SO4 = 1:1 [w/w]) added for the salinity treatments was 0, 2, 4 and 6% of the soil dry weight and was designated as S0–S3, respectively. The water consumption, biomass, osmolytes, such as proline and Na+, and the activities of antioxidant enzymes, such as superoxide dismutase (SOD) and peroxidase (POD), of alfalfa were measured during its early flowering stage. In general, the plant height, aboveground biomass, root biomass and water consumption of alfalfa increased with the decrease in soil salinity and increase in the amount of irrigation applied. When the salt >3 g kg−1, alfalfa could improve its stress resistance by increasing the contents of proline and Na+ and the activity of POD and decreasing the activity of SOD, but the aboveground biomass and water consumption decreased. However, alfalfa has a certain cross adaptation ability under water and salt stress at the branching stage, particularly when salt is less than 3 g kg−1. Compared with single water stress, adding an appropriate amount of salt (≤3 g kg−1) increased the contents of proline and Na+ and the activities of SOD and POD, which led to water consumption and aboveground biomass of alfalfa increases of 11.93% and 17.51%, respectively. In conclusion, the alfalfa was tolerant to moderate (3 g kg−1) salt stress. The alfalfa with higher proline, SOD and POD activity and Na+ was better able to yield well under salt stress. Meanwhile, combined with moderate irrigation (70–85% FC), the productivity of alfalfa was improved better. The results can provide a theoretical basis for the utilization of alfalfa in salinized land.

Changes in Physicochemical Properties of Typical Subtropical Soils under Different Treated Domestic Wastewater Irrigation Modes

Irrigation with treated domestic wastewater (TWW) affects the physicochemical properties of soils, but little research has been conducted for different soils in subtropical regions. Consequently, in order to evaluate the effects of domestic wastewater (treated by A2/O process) irrigation on the hydraulic properties, soil salinity and sodicity of four typical subtropical agricultural soils, a soil-column experiment was conducted for one year with eight cycles of wetting and drying. A clay soil (red soil), a silty clay soil (aquic soil), a loamy clay soil (purple soil), and a silty clay loam soil (paddy soil) were subjected to three irrigation modes: (a) cyclic irrigation with TWW (W1), (b) alternating irrigations with TWW and distilled water (W2), and (c) irrigation with distilled water as a control (CK). Our results indicated that EC values increased significantly (p < 0.05) with TWW irrigation for all the soils. TWW irrigation increased the concentrations of Na+, K+, Ca2+, Mg2+, and SAR, ESP values in the red soil, for the W2 treatment especially. In contrast, it decreased Na+, K+, Ca2+, Mg2+ accumulation and ESP values in the aquic soil. Moreover, the soil physical properties exhibited correlations with soil salinity. The saturated hydraulic conductivity (Ks) of the red soil, purple soil, and paddy soil were lower under the W1 and W2 treatments than CK, but the Ks of the aquic soil for W1 were 183.7% higher than that under CK. The unsaturated hydraulic conductivity (Kψ) of the purple soil and paddy soil decreased after TWW irrigation, but those of the aquic soil increased. The water-retention capacities (WRCs) of the TWW-irrigated red soil and aquic soil decreased as a consequence of a shift in the pore-size distribution toward wider pores, but the those of the purple soil and paddy soil improved, associated with narrower pores. The W2 treatment alleviated the impact of TWW on the aquic soil, purple soil, and paddy soil but negatively affected the physical properties, salinity, and sodicity of the red soil. Our results will provide useful information for managing soil and water under TWW irrigation in subtropical regions.

Fate of each period fertilizer N in Mollisols under water and N management: A 15N tracer study

For soil-crop systems, it is important to increase the retention of fertilizer N that is not effectively utilized by crops in stable forms in soil and reduce fertilizer N loss from agroecosystems through agricultural practices. However, it remains obscure how the fate of fertilizer N will be affected by water and N management. To further clarify the effects of water and N management on the fate of each period fertilizer N and residual fertilizer N amounts of different derived forms, a field experiment was conducted in Mollisols in Northeast China. This experiment combined a field plot experiment with a flied microplot 15N isotope experiment, and six treatments were performed: two irrigation management modes (controlled irrigation and flooded irrigation) and three fertilizer-N rates (85, 110 and 135 kg/ha). Additionally, the basal, tillering, and panicle fertilizer N were tracked by 15N-labeled urea to study the fate of each period fertilizer N. The present study showed that under controlled irrigation (CI), fertilizer-derived N in different forms increased with the increase N rate. Under flooded irrigation (FI), with the increase N rate, the residual organic nitrogen (NO) first increased and then decreased, and the other forms of fertilizer-derived N increased. In the total residual fertilizer N in soil, residual basal fertilizer N accounted for the highest proportion under the two irrigation modes, residual tillering fertilizer N accounted for the lowest proportion under FI, and panicle fertilizer N accounted for the lowest proportion under CI. NO accounted for the highest proportion of the residual amount of each period fertilizer N under CI and FI, while NO3--N accounted for the lowest proportion under CI, and fixed ammonium accounted for the lowest proportion under FI. Compared with FI, CI increased the total residual fertilizer N amount and promoted the conversion of residual fertilizer N into NO. The present study suggested that CI, as a water-saving irrigation mode, not only decreased agricultural water consumption but also increased fertilizer N retention in soil and enhanced the conversion of residual fertilizer N into NO. The establishment of appropriate water and N management has great potential for the regulation of residual fertilizer N in paddy soil.

The Influence of N2O Emission to Water and Nitrogen Coupling Mechanism in Black Soil under Drip Irrigation Mode

This experiment is aimed at revealing the main characteristics of N2O emission from soybean in black soil and clarifying the relationship between N2O emission and environmental factors; in this experiment, static chamber-gas chromatography field observation method was used; meanwhile, three different drip irrigation amounts (300 mm, 350 mm, and 400 mm) and five different nitrogen application amounts (0, 63, 72, 81, and 90 kg/hm2) were set up to study the effects of different coupling modes on soybean N2O emission and the relationship between N2O emission and environmental factors. The results showed that the peak value of N2O emission flux of soybean mainly occurred in July and August, and the amount of N2O emission flux in each growth period was flowering-podding period > branching period > seedling period > grain filling period. N2O emission increased with the increase of drip irrigation amount and nitrogen application amount. The effects of drip irrigation and nitrogen application on N2O emission were significantly different. Under the three drip irrigation modes, the N2O emission fluxes of most treatments were significantly correlated with the temperature in that day, and the soil temperature in different soil depths was significantly correlated with the N2O emission fluxes. The correlation relationship between the temperature of each soil layer under drip irrigation 300 mm and N2O emission fluxes was less than that under drip irrigation 350 mm and drip irrigation 400 mm. There was no significant correlation between N2O emission flux and NH4+-N and NO3-N, and there was no significant correlation between N2O cumulative emission and dry matter quality in the aboveground part of soybean. It shows that the emission of N2O itself is affected by multiple environmental factors and shows certain randomness. The research results can provide important theoretical basis and technical support for realizing nitrogen reduction and efficient utilization of soybean water and fertilizer in the black soil region of northeastern part of China.

Optimized fertigation mitigates N2O and NO emissions and enhances NH3 volatilizations in an intensified greenhouse vegetable system

Gaseous reactive nitrogen (GNr) losses (N2O, NO emissions and NH3 volatilization, etc.) in greenhouse vegetable fields (GVF) have received considerable critical attention. Much uncertainty still exists about GNr losses reduction under increasing vegetables demand and environmental policies in China. An experiment spanning four greenhouse vegetable growing seasons (cucumber and tomato) was conducted in North China Plain (NCP). It included four treatments, i.e., flood irrigation with no urea-N application (FU0), flood irrigation with conventional urea-N application (FUN), drip fertigation with conventional urea-N application (DUN), and drip fertigation with 50% reduction of urea-N application (DRUN). Obvious emission peaks of N2O, NO and NH3 flux were captured in the GVF after each fertilization and irrigation event. For FUN treatment, the mean annual area-scaled emissions of N2O, NO, and NH3 were 11.48, 1.66, and 44.90 kg N ha−1 yr−1, respectively; and the mean annual yield-scaled emissions of N2O, NO, and NH3 were 181.86, 23.04, and 800.07 g N t−1 yr−1, respectively. On the mean annual area-scaled and yield-scaled, the N2O emissions were significantly (P < 0.05) lower by 40.1 % and 32.3 %, and the NO emissions were lower by 23.5 % and 28.5 %, but the NH3 volatilization were significantly (P < 0.05) higher by 31.7 % and 49.0 %, respectively, for the DUN treatment than FUN. Also compared with FUN, in DRUN treatment, the mean annual area-scaled N2O emissions, NO emissions and NH3 volatilization were significantly reduced by 46.7 %, 52.4 % and 22.0 %, respectively; and the mean annual yield-scaled N2O emissions, NO emissions and NH3 volatilization were significantly reduced by 40.7 %, 57.1 % and 24.5 %, respectively. Moreover, compared with FUN treatment, DUN and DRUN treatment both alleviated the global temperature potential (GTP) at 20- and 100-year timescales. Overall, compared with conventional water and fertilizer regimes, only changing irrigation mode reduced N2O and NO emissions but increased NH3 volatilization losses in greenhouse cucumber-tomato cultivation system; reducing N application while changing irrigation methods had significant emission reduction effects on N2O, NO and NH3 at both the area-scaled and yield-scaled, and which is an effective water and fertilizer managements for greenhouse cucumber-tomato cultivation system.

A semi-empirical semi-process model of ammonia volatilization from paddy fields under different irrigation modes and urea application regimes

Both empirical models and process-based models of ammonia (NH3) volatilization simulation in paddy field have some disadvantages. This work describes a semi-empirical semi-process model, which combines the simplicity of empirical models with the precision of process-based models, and its combinatorial structure is sufficient for reproducing the characteristic course of NH3 volatilization in paddy fields under different irrigation modes and urea application regimes over time. A dataset consisting of seven rice seasons across three locations was used for model development. Performance indexes showed the model is good (R2 values ranged from 0.67 to 0.94). The influence of air temperature and wind speed on NH3 volatilization was not as great as our conventional understanding, and soil temperature was a more accurate indicator than air temperature for model development. Model performance was better where the less urea splits and the higher urea rate, but there was no significant difference between alternate wetting and drying (AWD) irrigation mode (average values of R2, IA, NSI, and RMSE were 0.82, 0.94, 0.96, and 0.53 kg ha-1 d-1) and flooding irrigation (FI) mode (average values of R2, IA, NSI, and RMSE were 0.86, 0.94, 0.96, and 0.58 kg ha-1 d-1). The ammonium nitrogen (NH4+-N) concentration and pH of surface water and soil water in paddy fields had the greatest impact on NH3 volatilization, and they were mainly related to the amount of urea applied. Splitting the urea application and delaying the first urea application are the fundamental countermeasures to reduce NH3 volatilization. The magnitude of developed model performance varied among rice cropping systems, irrigation modes, urea application regimes, and climatic regions, highlighting the need to understand why measured NH3 volatilization varies among locations. The new model may be a useful tool for predicting fertilizer efficiency of paddy fields applied urea, assessing NH3 volatilization factors, and reducing emission.

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.

Effects of Different Wastewater Irrigation on Soil Properties and Vegetable Productivity in the North China Plain

The interest in reusing wastewater for irrigation is being popularized in most countries. The objective of this study was to evaluate the effects of different wastewater and nitrogen fertilizer on soil fertility and plant quality, as well as to identify the optimal irrigation mode in the North China Plain. A total of nine treatments, including control (groundwater, no fertilizer), piggery wastewater, reclaimed water, and saline water, combined with nitrogen fertilizer (300 kg/ha and 200 kg/ha), were conducted in a greenhouse in 2019 (Xinxiang, Henan Province). Soil pH, electrical conductivity, organic matter, heavy metals contents, and cucumber yield and quality were analyzed. The results showed that: (1) compared with the underground water (control), soil pH value with a decrement of 0.21 units in piggery wastewater (PW), and 0.24 units in saline water treatments (SW). Soil electrical conductivity (EC) value significantly increased by 5.8~20.9% in PW and SW treatments, while there was no significant difference in EC in reclaimed water. The highest EC (770 µS/cm) was recorded in SW treatment. (2) No dramatic difference on the concentrations of soil lead (Pb) and cadmium (Cd) in the PW, RW, and SW treatments, compared with the control, but soil organic matter, copper (Cu), and zinc (Zn) concentrations in wastewater treatments were increased by 2.1~43.4%, 24.4~27.0%, and 14.9~21.9%, respectively. (3) There were no significant differences in cucumber yield and quality in RW treatment, while there was a slight decrease by 1.4% in yield in the SW treatment. The highest cucumber yield was observed in PWH treatment, with an increment of 17.5%. In addition, the contents of Vitamin C, soluble sugar, and protein were also improved by PW treatment. In this study, PW treatment showed the strongest ability to promote cucumber yield and quality, thus indicating that piggery wastewater irrigation with 300 kg/ha nitrogen would be the optimal practice in this region. Long-term study is necessary to monitor potential risk of heavy metals on the quality of soil and plant.