Soil Enzyme Activities with Greenhouse Subsurface Irrigation

Various environmental conditions determine soil enzyme activities, which are important indicators for changes of soil microbial activity, soil fertility, and land quality. The effect of subsurface irrigation scheduling on activities of three soil enzymes (phosphatase, urease, and catalase) was studied at five depths (0-10, 10-20, 20-30, 30-40, and 40-60 cm) of a tomato greenhouse soil. Irrigation was scheduled when soil water condition reached the maximum allowable depletion (MAD) designed for different treatments (-10, -16,-25,-40, and-63 kPa). Results showed that soil enzyme activities had significant responses to the irrigation scheduling during the period of subsurface irrigation. The neutral phosphatase activity and the catalase activity were found to generally increase with more frequent irrigation (MAD of -10 and -16 kPa). This suggested that a higher level of water content favored an increase in activity of these two enzymes. In contrast, the urease activity decreased under irrigation, with less effect for MAD of -40 and -63 kPa. This implied that relatively wet soil conditions were conducive to retention of urea N, but relatively dry soil conditions could result in increasing loss of urea N. Further, this study revealed that soil enzyme activities could be alternative natural bio-sensors for the effect of irrigation on soil biochemical reactions and could help optimize irrigation management of greenhouse crop production.

Yield and Quality Response of Cucumber to Irrigation and Nitrogen Fertilization Under Subsurface Drip Irrigation in Solar Greenhouse

The aims of this research were to compare subsurface drip irrigation scheduling and nitrogen fertilization rates in cucumber, and evaluate yield and quality of cucumber fruit, water （WUE）, irrigation water （IWUE）, and nitrogen use （NUE） efficiencies in the solar greenhouse in Southwest China. The irrigation water amounts were determined based on the 20 cm diameter pan （Ep） placed over the crop canopy, and cucumber plant was subjected to three irrigation water levels （I1, 0.6 Ep; I2, 0.8 Ep; and I3, 1.0 Ep） in interaction with three nitrogen fertilization levels （N1, 300 kg ha-1; N2, 450 kg ha-1; and N3, 600 kg ha-1）. The results showed that the cucumber fruit yield increased with the improvement of irrigation water. Irrigation water increased yields by increasing the mean weight of the fruits, and also by increasing fruit number. But the highest values of IWUE and WUE were obtained from I2 treatment. NUE significantly decreased with the improvement of N application, but increased by irrigating more water. The quality of cucumber fruit decreased with the improvement irrigation water and nitrogen fertilization. In conclusion, the optimum irrigation level and nitrogen fertilizer application level for cucunber under subsurface drip irrigation in the solar greenhouse in Southwest China were 0.8 Ep and 450 and 600 kg ha-1, respectively.

Tomato Root Response to Subsurface Drip Irrigation

Four depth treatments of subsurface drip irrigation pipes were designated as 1) at 20,2) 30 and 3) 40 cm depths all with a drip-proof flumes underneath,and 4) at 30 cm without a drip-proof flume to investigate the responses of a tomato root system to different technical parameters of subsurface drip irrigation in a glass greenhouse,to evaluate tomato growth as affected by subsurface drip irrigation,and to develop an integrated subsurface drip irrigation method for optimal tomato yield and water use in a glass greenhouse. Tomato seedlings were planted above the subsurface drip irrigation pipe. Most of the tomato roots in treatment 1 were found in the top 0-20 cm soil depth with weak root activity but with yield and water use efficiency (WUE) significantly less (P ---- 0.05) than treatment 2; root activity and tomato yield were significantly higher (P = 0.05) with treatment 3 compared to treatment 1; and with treatment 2 the tomato roots and shoots grew harmoniously with root activity,nutrient uptake,tomato yield and WUE significantly higher (P= 0.05) or as high as the other treatments. These findings suggested that subsurface drip irrigation with pipes at 30 cm depth with a drip-proof flume placed underneath was best for tomato production in greenhouses. In addition,the irrigation interval should be about 7-8 days and the irrigation rate should be set to 225 m3 ha-1 per event.

The Potential Contribution of Subsurface Drip Irrigation to Water-Saving Agriculture in the Western USA

Water shortages within the western USA are resulting in the adoption of water-saving agricultural practices within this region. Among the many possible methods for saving water in agriculture, the adoption of subsurface drip irrigation （SDI） provides a potential solution to the problem of low water use efficiency. Other advantages of SDI include reduced NO3 leaching compared to surface irrigation, higher yields, a dry soil surface for improved weed control, better crop health, and harvest flexibility for many specialty crops. The use of SDI also allows the virtual elimination of crop water stress, the ability to apply water and nutrients to the most active part of the root zone, protection of drip lines from damage due to cultivation and tillage, and the ability to irrigate with wastewater while preventing human contact. Yet, SDI is used only on a minority of cropland in the arid western USA. Reasons for the limited adoption of SDI include the high initial capital investment required, the need for intensive management, and the urbanization that is rapidly consuming farmland in parts of the western USA. The contributions of SDI to increasing yield, quality, and water use efficiency have been demonstrated. The two major barriers to SDI sustainability in arid regions are economics （i.e., paying for the SDI system）, including the high cost of installation; and salt accumulation, which requires periodic leaching, specialized tillage methods, or transplanting of seedlings rather than direct-seeding. We will review advances in irrigation management with SDI.

Evaluation of the efficiency of irrigation methods on the growth and survival of tree seedlings in an arid climate

Scarce and scattered precipitation in arid regions is detrimental for newly planted seedlings.It is essential to provide required water storage for seedlings in restoration projects in the first year of their establishment.The subsurface irrigation can be much more effective than the surface irrigation because of the regulation of water availability and reduction in water evaporation.We studied the effect of surface and subsurface irrigation methods on the growth and survival of four common tree species including heaven tree(Ailanthus altissima(Mill.)Swingle),China berry(Melia azedarach L.),white mulberry(Morus alba L.),and black locust(Robinia pseudoacacia L.)by installing underground clay reservoirs with different permeabilities in Isfahan City,Iran.Different amounts of animal manure and wheat straw were mixed with clay fraction and cooked in a pottery kiln at 900°C to produce reservoirs with different permeabilities.The experimental treatments consisting of irrigation and tree species were considered with a factorial arrangement in a completely randomized design with three replications in 2016 and 2017.Leaf water potential of seedlings,which is indirectly related to drought resistance,was measured by a portable pressure chamber.The results showed that saplings height,basal diameter,number of leaves,chlorophyll content and stomatal conductance were significantly(P<0.05)higher in the subsurface irrigation with low permeability than in the surface irrigation,but the number of branches of the studied species were not significantly(P>0.05)affected by the irrigation methods and different permeabilities of clay reservoirs.The clay reservoirs with low and medium permeabilities constantly provide better conditions for plant growth,and water with lower pressure and longer time intervals to the plant roots as compared with the reservoirs with high permeability.Analysis of variance of the data showed that year and interaction between year and permeability of reservoir had significant effects(P<0.05)on all growth parameters,except for the chlorophyll content.In addition,the highest percentage of survival was 100%associated with the subsurface irrigation and the control treatment had the lowest survival percentages of 60%,70%,80%and 100%for M.alba,M.azedarach,A.altissima and R.pseudoacacia,respectively.Finally,the values of leaf water potential showed that R.pseudoacacia was the most drought resistant species.

Modeling of Different Irrigation Methods for Maize Using AquaCrop Model: Case Study

Modeling of irrigation methods is one of the most important techniques that contribute to the future of modern agriculture. This will conserve water as water scarcity is a major threat for agriculture. In this study, AquaCrop model was used to model different irrigation methods of maize in field trails in Al-Yousifya, 15 km Southwest of Baghdad. Field experiments were conducted for two seasons during 2016 and 2017 using five irrigation methods including furrow, surface drip and subsurface drip with three patterns of emitter depth (10, 20 and 30 cm) irrigation. AquaCrop simulations of biomass, grain yield, harvest index and water productivity were validated using different statistical parameters under the natural conditions obtained in the study area. For 2016 and 2017 seasons, results of R2 were 0.98 and 0.99, 0.99 and 0.99, 0.99 and 0.97, and 0.8 and 0.73 for biomass, grain yield, harvest index and water productivity, respectively. The study has conducted that simulation using AquaCrop is considered very efficient tool for modeling of different irrigation applications for maize production under the existing conditions in the central region of Iraq.

Effects of topdressing ratio and frequency on the dry matter, yield, and quality of tomato and celery under a small amount of continuous subsurface drip irrigation

Compared with conventional full irrigation,the existing water-saving irrigation method achieves the purpose of water saving by actively controlling soil moisture.High-frequency irrigation can make the ideal conditions for soil water movement and root absorption of water and nutrients.This research used a plot experiment in a greenhouse and set up different fertilization amounts and frequencies during the growth stage to study the effects of small-amount and continuous subsurface drip irrigation on the dry matter,yield,and quality of tomato and celery.The results showed that the frequency of topdressing had a great influence on the dry matter accumulation of tomatoes,and the amount of topdressing had little effect on the fresh weight of the upper part of a tomato plant.The application of high-frequency fertilizer increased the dry matter accumulation in the underground part of the tomato.Under the premise given amount of total fertilization,the growth rate and yield of tomatoes were positively correlated with the amount of topdressing.The optimum fertilization frequency was 1 time during the first fruit stage,3 times for the second fruit stage,and 5 times for the third fruit stage,the yield during the fourth stage was increased with higher frequency,and the topdressing was started ahead of the fourth fruit stage when the diameter of fruit was 40 mm.The lower fertilization frequency during the early stage and higher fertilization frequency during the later stage can increase the yield of celery.The higher ratio of topdressing,the higher frequency during the early growth stage,and the lower frequency during the later stage can achieve the best quality of celery.

Experimental study on calculation model of labyrinth emitter discharge under subsurface drip irrigation

For different texture of soils,the grain composition is different with significant changes.Since the emitter of subsurface drip irrigation(SDI)is buried in the soil,emitter discharge is influenced by soil properties.An experiment was conducted to investigate the relationship between the soil properties with emitter working pressure and emitter discharge of SDI.Selecting three different grain composition soils,and emitter working pressure,as well as soil clay content,soil bulk density and initial soil moisture content respectively as influence factors of emitter discharge of SDI,the experimental scheme was gained by uniform design.A calculation model for determination of the SDI emitter discharge was established by regression analysis with the first two kinds of soil test data,and its reliability was verified by the third kind of soil test data.The model is simple with high accuracy,easy to use,and lays the foundation to study hydraulic elements of SDI field network,especially taking the soil clay content as an influencing factor has widened the scope of application of the model.The achievement is of great significance for design and management of SDI.

Efect of Post-Irrigation Aeration on Growth and Quality of Greenhouse Cucumber

Rhizosphere aeration, irrigation with aerated water, and post-irrigation aeration would positively impact crop growth and yield. The objective of this study was to determine the effect of 4 post-irrigation aeration levels on plant growth, yield, irrigation-use efficiency （IUE）, and fruit market and nutritional quality of greenhouse cucumber under subsurface drip irrigation （SDI） and furrow irrigation （FI）. The post-irrigation aeration levels were 0.00, 0.50, 0.75, and 1.00 times half the estimated porosity of the plot rhizosphere. The experimental design was a two-faetor split-plot in randomized complete blocks with irrigation （FI and SDI） as the main treatments and 4 aeration levels as the sub-treatments. Ridge and furrow main plots （2.4 m ~ 2.4 m） with 4 ridges were replicated 5 times. Each of the 4 ridges （1.44 m2 in area） in the main plots was used as a sub-treatment plot. The results showed that post-irrigation aeration enhanced greenhouse cucumber plant growth, yield, IUE, and fruit market and nutritional quality. These parameters generally increased with increasing aeration levels under both FI and SDI. The aeration effect was generally higher under SDI than FI, and the IUE under SDI was almost twice that under FI. Further investigation would be required to elucidate the plant physiological mechanisms and soil processes responsible for the observed effects.

Soil Phosphorus Distribution as Affected by Irrigation Methods in Plastic Film House

Water-saving irrigation methods have been increasingly used for vegetable cultivation in greenhouse or plastic film house. However, there is limited information concerning the effect of water-saving irrigation methods on soil phosphorus （P） behavior. In this experiment, drip and subsurface irrigation methods were applied, with furrow irrigation method as control, in Mollic Gleysols. Soil P distribution throughout the depth was significantly affected by irrigation methods. Total, Olsen, organic and inorganic P contents were greater in the topsoil （0-10 and 10-20 cm） than in the subsoil （20-30, 30-40, 40-50 and 50-60 cm）. The Olsen P content throughout 0-60 cm layer under drip and subsurface irrigation treatments was lower than that under the furrow irrigation treatment. However, the total, organic and inorganic P contents from 20 to 60 cm under drip irrigation treatment were higher than or close to those under furrow irrigation treatment, but were lower under subsurface irrigation treatment than under furrow irrigation treatment. Under subsurface irrigation treatment, the contents of total, organic and inorganic P at the 0-10 cm layer were 78.0%, 1.3% and 3.7% greater than those at the 10-20 cm layer, respectively. But Olsen P content at the 10-20 cm layer was 5.7% larger than that at the 0-10 cm layer. These suggested that soil P behavior could be manipulated by soil water management to some extent. 在

Impact of oxygation on soil respiration, yield and water use efficiency of three crop species

Oxygation refers to irrigation of crops with aerated water,through air injection using the venturi principle or the supply of hydrogen peroxide in the root zone,both using subsurface drip irrigation(SDI)system.Oxygation improves water use efficiency(WUE),producing more yield and,and therefore,optimizes the use of drip and SDI.But the efficiency of oxygation is quite possibly dependent on a number of factors.The primary objective of this study was,therefore,to quantify the effects of oxygation,emitter depths and soil type on crop root zone oxygen content,soil respiration,plant physiological response,biomass yield,quality and WUE of three crop species.Methods This study investigated the potential of oxygation to enhance soil respiration,plant growth,yield and water use efficiencies(WUE)of cotton and wheat in experiments in enclosed heavy-duty concrete troughs(tubs)and pineapple and cotton in field experiments.Experimental treatments in tubs for wheat included comparisons between two soil types(vertisol and ferrosol)and superimposed were two oxygation methods(Mazzei air injector and Seair Diffusion System)compared to a control,and for cotton,emitters at two depths using Mazzei air injectors were compared to a control.The field experiments compared Mazzei air injectors and a control for cotton in Emerald and pineapple in Yeppoon,both in central Queensland,Australia.Important findings In all experiments,soil oxygen content and soil respiration markedly increased in response to the oxygation treatments.The O2 concentration in the crop root zone increased by 2.4–32.6%,for oxygation compared to control at the same depth.The soil respiration increased by 42–100%.The number of wheat ears,leaf dry weight and total dry matter were significantly greater in Mazzei and Seair oxygation compared to the control.Fresh biomass of wheat increased by 11 and 8%,and dry weight of wheat increased by 8 and 3%in Mazzei and Seair oxygation treatments compared to the control,respectively.Likewise,the irrigation water use efficiency increased with oxygation compared to the control in wheat.The yield,WUE and number of other physiological parameters in wheat were enhanced in vertisol compared to ferrosol.The seed cotton yield in the tub experiment increased with oxygation by 14%,and significant differences for fresh biomass,dry matter and yield were also noted between oxygation and the control in the field.Lint yield and WUE both increased by 7%using Mazzei in the cotton field trial during 2008–09.There were significant effects of oxygation on pineapple fresh biomass,and dry matter weight,industry yield and a number of quality parameters were significantly improved.The total fruit yield and marketable increased by 17 and 4%and marketable WUE increased by 3%using Mazzei.Our data suggest that the benefits of oxygation are notable not only for dicotyledonous cotton but also for monocotyledonous wheat and pineapple representing different rooting morphologies and CO_(2) fixation pathways.