Pivot Irrigation Research Articles

An Explicit Equation for the Maximum Water Application Depth in Center Pivot Irrigation

A simple explicit formula was derived to determine the maximum irrigation depth (Dmax) that can be applied per irrigation without any runoff under a center pivot and/or linear move irrigation system. The analysis is built on the assumption that Dmax is achieved when the water application rate is tangential to the Green-Ampt infiltration rate function. The surface storage was not considered here but tillage effects can be inherently incorporated if parameters of the Green-Ampt equation are properly measured. A power form formula was proposed to simulate the infiltration rate, while the application rate pattern had a parabolic shape. The proposed equation for Dmax is a function of soil saturated hydraulic conductivity, sorptivity, and the peak application rate. Numerical examples covering different combinations of soil properties and peak application rates indicated the high accuracy of the proposed formula with maximum and average absolute errors of 1 and 0.4 mm from the numerical stepwise solution, respectively. The quick calculation of Dmax here allows us to easily estimate a minimum lateral speed that will not trigger runoff under center pivots.

A Pivotal New Approach to Groundwater Quality Assessment

Areas of intensive agriculture and irrigation are prone to groundwater nitrate contamination, which can threaten drinking water supplies. Irrigation center pivots are a common feature in heavily irrigated regions and have the potential to provide insight into subsurface redox chemistry. In this study, we hypothesized that the same geochemical condition(s) that causes rust staining on center pivot systems will strongly influence groundwater nitrate concentrations. In south central Nebraska, 700 center pivot irrigation systems were classified by appearance of iron staining (full rust, part rust, or no rust) using Google Earth imagery and/or ground-based surveys. Ground-based observation of 270 center pivots yielded the same classifications as Google Earth imagery 83% of the time. Groundwater nitrate concentrations correlated with pivot classifications show lower nitrate concentrations in full rust and part rust pivots when compared with no rust pivots. The novelty of this work is to provide a framework for understanding groundwater quality using an inexpensive method applicable to both established and developing agricultural communities.

Development of center pivot irrigation farmlands from 2009 to 2018 in the Mu Us dune field, China: Implication for land use planning

Development of center pivot irrigation farmlands from 2009 to 2018 in the Mu Us dune field, China: Implication for land use planning

Crop response to thermal stress without yield loss in irrigated maize and soybean in Nebraska

Thermal sensing provides rapid and accurate estimation of crop water stress through canopy temperature data. Canopy temperature is highly dependent on the transpiration rate of the leaves. It is usually assumed that any reduction in crop evapotranspiration (ET) leads to crop yield loss. As a result, an increase in canopy temperature due to a decrease in crop ET would indicate crop yield loss. This research evaluated the hypothesis that crop water stress could be detected using canopy temperature measurements (increased leaf temperature) from infrared thermometers (IRTs) before incurring crop yield loss. This would be possible in a narrow range when the photosynthesis rate (and carbon assimilation) is limited by solar radiation (energy-limiting water stress) while the leaf has abundant carbon dioxide for photosynthesis. Once photosynthesis becomes limited by carbon dioxide (carbon-dioxide-limiting water stress), then yield reduction would occur. In this field experiment, measured response variables included the integrated crop water stress index (iCWSI), ET, and crop yield for maize and soybean during the 2020 and 2021 growing seasons. The irrigation was applied at four different refill levels: rainfed (0%), deficit (50%), full (100%), and over (150%). The irrigation depth was prescribed using four different irrigation methods. The field was irrigated with a center pivot irrigation system, which was also used as a platform to mount IRT sensors. The iCWSI thresholds required for irrigation management were determined using the iCWSI dataset collected in 2020. The low, medium, and high iCWSI thresholds were 120, 150, and 180, respectively for maize and 110, 130, and 150, respectively for soybean. These thresholds should be updated with iCWSI data from future studies in this region to increase the credibility of the thresholds for irrigation management. The mean iCWSI values for consecutive days after a wetting event substantially increased with time for each irrigation level and a larger range in iCWSI values was observed among the irrigation levels after three days from a wetting event. The seasonal iCWSI for different levels were found to be negatively correlated with seasonal evapotranspiration for both years. The correlations between seasonal ET and crop yield were significant with the rainfed and deficit levels for maize (p-value < 0.001) and soybean (p-value = 0.04) in 2020. The iCWSI and yield data for the fully watered plots indicated that thermal stress was detected using the sensing system without incurring yield loss (i.e., energy-limiting water stress). The ET and yield data for 2021 indicated that reduction in seasonal crop ET did not result in yield loss which also supported the hypothesis. Future studies should investigate whether this phenomenon of detecting crop water stress in an early stage without yield loss is observed in other climates and locations.

Water-energy nexus: A systematic analysis and evaluation of a center-pivot irrigation system

ABSTRACT Water-energy nexus plays a crucial role in addressing the issue of water wasting as well as planning, developing, and optimization of the agricultural product irrigation demands. The objective of this paper is to improve the water and energy use in value crops irrigated by center pivot systems under conventional irrigation planning in southern Algeria. This study is based on the field evaluation of the real water and electrical energy consumption, in two types of center pivot systems, large pivots and traditional Mini-Center Pivot Systems in two different areas (Ouargla and El Oued). Over two years, irrigation campaigns on six pivots systems with six different crops were analyzed to evaluate and characterize their water and electrical energy use. The CROPWAT model was used to determine the crop water requirements and compared with the water volumes currently applied by conventional irrigation planning. The results showed that there was over-consumption of water followed by high electrical energy use due to the poor planning of irrigation, which was generally excessive. In addition, the amount of water applied by conventional irrigation planning and that estimated by CROPWAT do not coincide during the most stages of crop growth. Closer inspection of the results shows that the irrigation water use efficiency for different crops was low and ranged between 0.25 and 3.27 kg/m3 due to the Over-irrigation. Furthermore, the modern pivots presented the most efficient equipment in terms of Energy Use Indicators with 1.1 kW ha−1 while the average of the traditional mini pivots was four times more (4.15 kWh−1). No significant difference was evident between the present specific consumption Es (in the average of 0.274 kWh m−3) and those reported in the literature due to high power installed in the pumping station for Mini-Center Pivot Systems. Therefore, the study findings are expected to draw the attention of decision-makers to the extent of wasting water and energy. Also, these findings reveal the harmful effects of farmers’ incorrect irrigation practices and motivate them to take strong measures toward sustainable agriculture.

Irrigation management zone strategies impact assessment on potential crop yield, water and energy savings

In irrigated agriculture, soil spatial variability is a primary factor for low irrigation efficiency. In regions such as the Brazilian Cerrado, where there is a continuous growth of irrigated agriculture and limited water supplies, it is important to seek alternatives to reach an efficient and sustainable irrigated agriculture. In this context, precision irrigation has great potential. Better strategies must be established, especially for center pivot irrigation conditions. Irrigation considering management zones is a promising option; however, criteria must be set to delimitate management zones and evaluate irrigation performance in such situations. This study aims to assess the impact of the use of management zones on irrigation performance. Therefore, two center pivots, PivoBHBV and PivoBHALPA, with distinct soil water physical traits, were evaluated. Two management zones strategies were considered to carry out the simulations. One of the strategies was based on regions in the format of square grids with areas of 25, 100 and 225 m2. In the other strategy, the unsupervised grouping algorithm Fuzzy C-Means was used to create management zones. The irrigation performed on those management zones was assessed by comparing their performance with the irrigation conducted in the grid areas. The irrigation management zones were delimited based on the interpolated maps of soil available water capacity (AWC), and the management was conducted individually for each zone. The simulations were made through a model developed with the Python language. The results indicate similarity between the irrigation with management zones and the grid irrigation, as it did not significantly increase water and energy demands or reduce soybean yield. Precision irrigation practiced management zones increased irrigation efficiency, reducing the effect of soil spatial variability. The total irrigation depth applied was, on average, 1.47 % lower than the irrigation by grids. Comparing the grid and the management zones irrigations, water and energy savings potential and the average yield increase potential were 1.85 %, 1.75 %, and 0.41 %.

Annual Trends of Soil Moisture and Rainfall Flux in an Arid Climate Using Remote Sensing Data

The water crisis is still a major issue in Qatar. Seawater desalination has been strongly implemented in the Persian Gulf region. However, it is costly and there is corrosion in piping materials and other equipment. Hence, there is a vital need to detect groundwater resources in Qatar. Various factors affect the variability of groundwater in Qatar including hydrogeological aspects, climate change, drawdown and abstraction, rainwater harvesting, desertification, and population growth. In this study, we employ the Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System (FLDAS) to monitor annual variations of soil moisture (SM) in the depth of 1–2 m (as an indicator of groundwater) and rainfall flux (RF) from 1982 to 2019. The results show that SM and RF anomalies were positive from 1982 to 2000 (except 1992). In contrast, these anomalies became negative during 2001–2019 (expect 2001 and 2018), implying the drawdown of groundwater resources. Drier years (i.e., negative RF anomaly) in the recent 19 years (2001–2019) reduced SM and led to a negative SM anomaly. The Mukaynis and Wadi Jallal regions (located in Al Rayyan and Al Wakrah municipalities, respectively) had the highest RF and SM from 1982 to 2019. The center-pivot irrigation systems close to the Mukaynis and Wadi Jallal regions indicate their accessibility to groundwater resources in Qatar. Moreover, these regions have the lowest risk of salinization and groundwater vulnerability. In addition, annual trends of groundwater storage (GWS) retrieved from the Gravity Recovery and Climate Experiment (GRACE) from 2003 to 2019 have been presented. This study is beneficial for detecting and monitoring groundwater resources for the sustainable management of water resources in arid environments.

Productivity and Quality of Sugar Beet in Relation to Sowing Methods and Plant Density Under Center Pivot Irrigation System

Productivity and Quality of Sugar Beet in Relation to Sowing Methods and Plant Density Under Center Pivot Irrigation System

Dual-Diameter Laterals in Center-Pivot Irrigation System

Design strategies to enhance modern irrigation practices, reduce energy consumption, and improve water use efficiency and crop yields are fundamental for sustainability. Concerning Center-Pivot Irrigation Systems, different design procedures aimed at optimizing water use efficiency have been proposed. Recently, following a gradually decreasing sprinkler spacing along the pivot lateral with constant diameter and sprinkler flow rate, a new design method providing a uniform water application rate has been introduced. However, no suggestions were given to design multiple-diameter laterals characterized by different values of the inside pipe diameter. In this paper, first the previous design procedure is briefly summarized. Then, for the dual-diameter center pivot laterals a design procedure is presented, which makes it possible to determine pipe diameters that always provide sprinkler pressure heads within an admitted range. The results showed that for the assigned input parameters, many suitable solutions can be selected. The lateral pressure head distributions were compared to those derived by the common numerical step by step solutions, validating the suggested simplified procedure. An error analysis was performed, showing that the relative error, in pressure heads, RE, was less than 2.3%. If imposing the mean weight diameter, Dm, equal to its minimum value, the optimal pressure head tolerance of the outer lateral, δI, amounting to about 2%, with the RE in pressure heads being less than 0.4%, which makes the suggested procedure very accurate. Several applications were performed, compared, and discussed.

Reinventing the wheel: adapting a traditional circular irrigation system to ‘modern’ agricultural extensions in Algeria’s Sahara

One of the most elaborate community initiatives for the management of groundwater consists of managed aquifer recharge and use. In the oases in the M’zab valley in the Algerian Sahara, the collective action that upholds these initiatives has been challenged in past decades by the development of intensive groundwater use with individual pumps in new agricultural areas. However, faced with water shortage and inspired by the more circular irrigation practices in oases, farmers are increasingly creating local use loops in these extension areas by installing recharge devices and using water more carefully. This study analyzes the functioning of the circular managed aquifer recharge and use system in Beni Isguen oasis, and how farmers have reinvented it in agricultural extensions, creatively combining it with modern technologies to engage in market-oriented agriculture. Reinventing circular practices in new agricultural extensions can contribute to more environmentally sustainable forms of agriculture.

Multi-Level Influences on Center-Pivot Irrigation Adoption in Alabama

Rates of poverty and economic inequality in rural Alabama are among the nation's highest and increasing agricultural productivity can provide a needed boost to these communities. The transition from rain-fed to irrigation-fed (RFtoIF) agriculture has significantly increased farm productivity and profitability elsewhere in the United States. Despite this potential to enhance stability and resilience in rural economies, irrigated cropland accounts for only 5% of Alabama's total cropland as numerous barriers remain to irrigation adoption. To encourage RFtoIF transition, it is imperative to identify the challenges faced by individual farmers at farm, community, and state levels. This study presents a multi-level mixed effects survival analysis to identify the physiographic, socioecological, and economic factors that influence the location and timing of irrigation adoption. We integrate spatiotemporal cropland and climatological data with field-verified locations of center-pivot irrigation systems, local physiographic characteristics, and parcel-level surface water access and average well depth. Access to surface water, costs to access groundwater, and soil characteristics were generally important influences in all regions, but regions were differentiated by the extent to which new irrigation was more responsive to social influences vs. precipitation and price trends. Our findings also highlighted the diversity of farming conditions across the state, which suggested that diverse policy tools are needed that acknowledge the varying motivations and constraints faced by Alabama's farmers.

Energy consumption reduction of a center-pivot with the use of a variable-frequency drive

Pressure demand of a center-pivot can be controlled by variable frequency drives during irrigation system operations, leading to a rational use of electrical energy. However, numerous studies encountered problems due to the lack of field data to perform the simulations. The objective of this study was to simulate the reduction of the average value of the active electrical power required to drive the pumping unit of a center-pivot irrigation system by controlling the rotational speed through a frequency inverter. The simulation was conducted considering a complete rotation of the lateral line of a central pivot, installed in an area of 70-ha, in the municipality of Formiga-MG. The simulation demonstrated the possibility of reducing the active electrical power required for the pivot pump by 18%, from an average of 131 to 107 kW. For 1300 pumping hours per year, the investment's payback time would be two and four years for the highest (R$ 0.48 kWh-1) and lowest energy cost (R$ 0.32 kWh-1), respectively. Results suggest that irrigated areas by center-pivot with variations of topographic altitude require technical-economic evaluations for using frequency inverters.

Maize response to irrigation and nitrogen under center pivot, subsurface drip and furrow irrigation: Water productivity, basal evapotranspiration and yield response factors

Information and data about quantification and comparison of crop water productivity indices for various irrigation levels and methods and nitrogen (N) application timings “simultaneously” under the same conditions do not exist. Unprecedented and extensive field experiments were conducted for maize (Zea mays L.) in 2016 and 2017 under center pivot (CP), subsurface drip irrigation (SDI) and furrow irrigation (FI) methods with full irrigation treatment (FIT), 80 % FIT, 60 % FIT and rainfed treatment (RFT) with three N application timings. N treatments were: (i) traditional (TN), (ii) non-traditional-1 (NT-1) and (iii) non-traditional-2 (NT-2). Irrigation-yield production functions (IYPF); evapotranspiration-yield production functions (ETYPF), basal evapotranspiration (ETb), crop water productivity (CWP), irrigation water use efficiency (IWUE); evapotranspiration water use efficiency (ETWUE) and yield response factors (Ky) were quantified for each treatment and irrigation method. SDI method required the least seasonal irrigation amount in achieving maximum yield, followed by CP (>~30 mm more than SDI) and FI (>~55 mm more than SDI). Average crop water requirement for achieving maximum grain yield varied among the N treatments within and between the irrigation methods. Irrigation amounts for achieving maximum yields were about 160, 175 and 175 mm in TN, NT-1 and NT-2 nitrogen treatments, respectively, in the CP method; 130, 150 and 150 mm in TN, NT-1 and NT-2 nitrogen treatments, respectively, in the SDI method; and 184 mm in TN management in the FI method. The highest grain yield production per 25.4 mm of applied irrigation followed the order of CP-TN (2.07 Mg ha−1)>SDI-NT-2 (1.91 Mg ha−1)>FI-TN (1.22 Mg ha−1). Across all treatments for the given irrigation method, the highest averaged CWP of 3.00 kg m−3 (slope = 0.067 kg m−3) was observed in the SDI method (p < 0.05) followed by 2.84 kg m−3 (slope = 0.052 kg m−3) in the CP method (p < 0.05) and 2.51 kg m−3 (slope = 0.046 kg m−3) in the FI method. The lowest ETb was observed in FI-TN (169 mm), followed by CP-NT-2 (172 mm) and SDI-TN (255 mm). For two consecutive years, N treatments did not have significant (p > 0.05) influence on IWUE in the CP or SDI methods. The highest IWUE, CWP and ETWUE were always obtained with limited irrigation treatments (60 % FIT and/or 80 % FIT) whereas the lowest with FIT. Maize under limited irrigation management had Ky < 1 with CP, SDI and FI along with lower Ky values than the respective TN treatment in CP and SDI, suggesting that the yield reduction is impacted to a lesser degree from the magnitude of water stress. The overall conclusion disclosed that utilizing the combination of limited irrigation (80 % FIT) with NT-1 fertigation under SDI and CP, while 80 % FIT under FI can be viable management practices for achieving high grain yield and CWP in conditions similar to those presented in this research.

Using satellite imagery to compare land cover and water resources in two counties of the Nebraska Sandhills

The Nebraska Sandhills comprise the most intact grassland habitat in the world and 95% of land use consists of low intensity cattle grazing. Water is a key resource for cattle and for growing hay forage in this semi-arid grassland. Ranchers rely on either naturally occurring wet meadows or center pivot irrigation systems (CPIS) to produce hay. With the possibility of climate change creating more frequent extreme weather events, more flooding events or severe droughts could affect land and water resources in the Sandhills. With potentially more wet/dry extremes in the future, an understanding of the way water resources respond, and the different strategies of landowners, will be important in assessing the overall resilience of the Nebraska Sandhills in the face of a changing climate. We compared two adjacent, similarly sized, counties, Grant and Hooker, in the central Sandhills that differ in the amount of naturally occurring, ground water-fed meadows during the period 2002-2019, spanning wet and dry years. ArcGIS and the USDA’s Cropland Data Layer (known as “CropScape”), an annual, satellite imagery-derived, land cover map, were used to quantify overall landcover, especially the cover of wet meadows and the number of CPIS. In 2016, an average-to-moderate precipitation year, Grant County had approximately 10 times more open water area and 9 times more wet meadow area than Hooker County. In contrast, Hooker County had 19 times more barren ground area and nearly twice as many CPIS as Grant County. Furthermore, in drought years, the amount of barren ground increased in both counties, nearly doubling in Hooker County in 2006, a year when annual precipitation was only 66% of normal precipitation rates. Drought also increased the acreage devoted to irrigated crops, particularly in 2006 in both counties, with nearly two times as many acres in Grant County and nearly five times as many acres in Hooker County. Additionally, open water acreage decreased by nearly 50% following the 2006 drought and wetland cover types increased. This analysis showed that different Sandhill counties have contrasting water resources, with an abundance of naturally occurring wet meadows in Grant County, whereas Hooker County has fewer wet meadows and more CPIS. Furthermore, our analysis suggests that the landscape changes during drought years, with a decline in wet meadows, an increase in barren ground and an increase in CPIS and other irrigated systems for crops. In a changing climate, with potentially more extremes in precipitation, the diversity of strategies exemplified by these two counties will be important to inform adaptative responses. Overall, this research will contribute to a better understanding of the sustainability of land use and the future of groundwater resources in the Nebraska Sandhills.

Effect of Center-Pivot Irrigation Intensity on Groundwater Level Dynamics in the Agro-Pastoral Ecotone of Northern China

Groundwater-based irrigation is an effective buffer against water disconnects during droughts in areas of intensive agriculture. However, it is difficult to implement effective measures to sustainably utilize aquifers due to the unclear understanding of irrigation intensity in the agro-pastoral ecotone. To explore the influence of regional irrigation intensity on groundwater level (GL), we investigated the dynamics of Kernel density for irrigation well from 2000 and the changed GL (ΔGL in three groups) in a typical center-pivot irrigation (CPI) area (about 1,000 km2). The results showed that the implementation of CPI systems caused a rapid land-use change from natural grassland (NG) to cultivated pasture (CP). The observed ΔGL in deeper group (0.63 m yr−1, GL &amp;gt; 20 m) was significantly (p &amp;lt; 0.05) higher than that in shallower group (0.38 m yr−1, GL &amp;lt; 10 m) and medium group (0.43 m yr−1, 10 m &amp;lt; GL &amp;lt; 20 m). The predicted ΔGL and GL were significantly and positively correlated with the CPI well density (R2 = 0.447 and 0.429, p &amp;lt; 0.001), respectively, and showed a fitted plane function based on the variables (R2 = 0.655, p &amp;lt; 0.001). It indicted that the intensive cropping in the agro-pastoral ecotone profoundly changed regional irrigation intensity, resulting in a rapid response of the GL. To reduce the risk of increased irrigation costs and ensure sustainable availability of groundwater, it’s necessary to control the density of CPI systems in hotspot areas, and implement water-saving measures to balance water usage and recharge rates for sustainable groundwater management.

Economic Viability of Ultrasonic Sensor Actuated Nozzle Height Control in Center Pivot Irrigation Systems

The coverage of center pivot irrigation systems used around the world has increased. One potential factor driving their adoption is improved water application efficiency relative to some other sprinkler or surface irrigation approaches. Center pivot irrigation systems may be further improved by dynamic elevation spray application (DESA). DESA systems adjust the nozzle height in response to plant growth and canopy heterogeneities. The DESA approach is relatively new and there is uncertainty in its economic viability and worthiness of further investigation. Thus, an economic scenario analysis was performed to explore the potential economic benefits of DESA based on permutations of irrigation pivot efficiency without DESA, water-saving potential of DESA, and water cost. The weighted costs and benefits of the height-adjusted approach for a set of water cost savings scenarios showed the net return price with the water cost savings per season. We show that DESA could have economic viability at current component costs and is worthy of further investigation and refinement.

Spatiotemporal dynamics of agricultural areas with central pivot using orbital remote sensing in the Brazilian semiarid

It is essential to know the dynamics of agricultural areas through surface energy balance components such as radiation balance, evapotranspiration, and soil moisture for the sustainable management of water use in irrigation. In the present study, we undertook to monitor and evaluate the spatiotemporal dynamics of an irrigated area with a center pivot in a region of the Brazilian semiarid region, based on physical and water parameters of the energy balance, using remote sensing techniques. The work was developed using three Landsat-8 satellite images, implementing the Surface Energy Balance Algorithms for Land (SEBAL), responsible for extracting geospatial information. In addition, surface meteorological data were used for image corrections and calibrations. The results presented, from thematic maps, monitoring of the spatiotemporal dynamics of irrigated areas, specifying mainly the production of irrigated corn with pivot. Thus, because of the physical-water parameters, photosynthetically active radiation irrigated areas and water deficit were identified, with higher and lower values of the radiation balance, evapotranspiration, and soil moisture, respectively. Therefore, spatiotemporal monitoring of the dynamics of irrigated areas can help in planning and managing the proper management of agricultural systems for the sustainable use of water in the Brazilian semiarid region. The MNDWI proved to be sensitive and efficient to analyze the dynamics of the presence of water in center pivot irrigation and can be an effective part of irrigation management in the region.

Maize response to coupled irrigation and nitrogen fertilization under center pivot, subsurface drip and surface (furrow) irrigation: Soil-water dynamics and crop evapotranspiration

Determination of crop evapotranspiration (ETc) and root zone soil-water dynamics/distribution coupled with nitrogen (N) management strategies is important for effective management of agricultural fields for enhancing production efficiency. However, limited data and knowledge exist that sufficiently inform how soil-water dynamics and ETc response may vary with coupled irrigation levels and different N application timings under different irrigation methods. Extensive field experiments were conducted in 2016 and 2017 under center pivot (CP), subsurface drip irrigation (SDI), and furrow irrigation (FI) at full irrigation treatment (FIT), 80% FIT, 60% FIT, and rainfed treatment (RFT) with N application timing treatments of traditional N (TN), non-traditional-1 (NT-1), and non-traditional-2 (NT-2) to quantify and compare seasonal maize (Zea mays L.) grain yield, soil-water dynamics, ETc, and ETc vs. seasonal irrigation and total water supply relationships. Soil-water status and plant water extraction exhibited substantial differences between the irrigation levels and N management and with the irrigation methods. Irrigation method significantly (p < 0.05) influenced ETc. CP had significantly higher ETc than SDI; and SDI had significantly higher ETc than FI. The NT-1 and NT-2 treatments had significantly higher ETc than TN. ETc was greatly influenced by the water availability more than N timing applications. The slope of maize ETc exhibited inter-annual and intra-annual variation between N treatments, irrigation methods, and years. CP had higher slope than FI and SDI and FI had higher slope than SDI under traditional and NT N management in both years (except NT-2 at SDI in 2017). These important findings can provide guidance to improve maize production efficiency by considering the coupled irrigation and N management strategies under different irrigation methods.

EFFECT OF VIRUS AND MYCOPLASMA DISEASES ON PRODUCTIVITY OF ALFALFA HAY CULTIVARS

Purpose: To evaluate the productivity of different alfalfa hay cultivars under the effect of local virus and mycoplasma diseases. Methodology: The study was conducted under center pivot irrigation system similar to TADCO mechanized alfalfa hay crop production. Results: Imported alfalfa hay cultivars were found infected with three virus and mycoplasma diseases: alfalfa enation virus, alfalfa mosaic virus and alfalfa witches' broom. Infections with these diseases lead to a severe reduction on the productivity of alfalfa hay cultivars in the third cropping season. Alfalfa enation virus was found to cause the most economic damage to the alfalfa hay crop, and the percentage yield reduction from this disease reached 17.6, 36.8% in the second and third seasons of cultivation respectively. Unique Contribution to Theory, Practice and Policy: The authors recommended to grow alfalfa hay cultivars with less susceptibility to virus diseases infections as we found variability in the productivity of the tested cultivars. The study also recommends to grow alfalfa hay cultivars under mechanized system for two seasons as we observed significant yield reduction in the third season due to high infestation with weeds and grasses which affected the hay quality. In the first field trial (1999 - 2002), productivity of alfalfa hay cultivars CUF 101 and Siriver reached above 30 M.T. /Ha under aphid-controlled conditions. In the second field trial (2002 - 2004), alfalfa hay productivity of the cultivars Fast Grow, SW 9500, Magic (SW 9301) and Super Supreme reached above 30 M.T./Ha in the first season 2003; and in the second season 2004, productivity of Magic, Fast Grow and Super Supreme reached above 26 M.T./Ha. Productivity over the two seasons 2003 and 2004 shown Fast Grow and Magic were the highest with 60.38, 59.85 M.T./Ha. respectively.

Optimizing Center Pivot Irrigation to Regulate Field Microclimate and Wheat Physiology under Dry-Hot Wind Conditions in the North China Plain

The dry-hot wind climate is one of the major agro-meteorological disasters associated with high temperature, low humidity, and specific wind forces, which seriously affects the yield of wheat in the North China Plain. A field experiment was conducted to investigate the field microclimate, net photosynthetic rate, chlorophyll content of flag leaves, grain filling rate, and wheat yield after sprinkler misting under the condition of a dry-hot wind climate in the 2018 and 2019 seasons. Two travel speeds, full and half speed, and the corresponding irrigation amounts of 2.5 and 5 mm were used by a center pivot irrigation system during dry-hot wind conditions. A treatment without irrigation was applied as a control. The results showed that the air temperature and relative air humidity were greatly improved within 60 min after irrigation, especially in the upper part of the canopy. The net photosynthetic rate of flag leaves under 5 mm irrigation was higher than that under 2.5 mm irrigation during the middle and late grain filling periods. The adverse effects of dry-hot wind on the chlorophyll content of the flag leaves were mainly concentrated in the late grain filling stage. In the two years of the experiment, the average 1000-grain weights of 5 and 2.5 mm of irrigation treatments were 4.3 and 2.8% higher, and the grain yields were 5.8 and 3.3% higher, respectively, than those of the non-irrigated yields. Overall, applying a small amount of water between 12:00–14:00 with a center pivot before the occurrence of dry-hot wind is an effective means to regulate the field microclimate and produce more yield in the North China Plain.