Dorota Z. Haman

Rainfall Intensity-Duration-Frequency Relationships for Andhra Pradesh, India: Changing Rainfall Patterns and Implications for Runoff and Groundwater Recharge

Accurate and current rainfall characterization is an important tool for water-related system design and management. Updated rainfall intensity-duration-frequency (IDF) relationships in peninsular India were developed; impacts on runoff and groundwater recharge attributable to changes in rainfall characteristics are discussed. Two data sets were used from gage in Hyderabad city, the capital of Andhra Pradesh: hourly rainfall data for the 19 years from 1993–2011 and daily rainfall data for the 30 years from 1982–2011. Hourly data were used to develop updated rainfall IDF relationships; daily data were used for trend analysis of threshold-based rainfall events. IDF curves were developed for return periods of 2, 5, 10, 15, 25, 50, 75, and 100 years for 1-, 2-, 4-, 8-, and 24-h durations. The updated IDF relationships showed a significant change in rainfall characteristics compared with older relationships for the region surrounding Hyderabad, India; they showed greater rainfall intensities across all durations and return periods. Greater intensity storms may reduce groundwater recharge and increase runoff, making the surface storage of runoff increasingly important to enhance recharge and reduce flooding risks.

Evapotranspiration and crop coefficients for young blueberries in Florida

A three-year study of water use by two species of cultivated blueberry was conducted. The experiment was performed on two rabbiteye (Vaccinium ashei Reade) varieties, Premier and Powderblue, and one highbush (Vaccinium corymbosum L.) variety, Sharpblue. Water was applied to the plants using a microirrigation system. Irrigations were triggered at three soil water tension levels: 10-kPa, 15-kPa, and 20-kPa. Water use for both species was monitored using drainage-type lysimeters and a water budget method. Grass reference crop modified coefficients for the modified Penman equation (Burman, 1980) during the first three years of establishment were developed based on the 10-kPa treatments for both species. Modified crop coefficients for microirrigated highbush blueberries were below 0.2 during the first two years of plant establishment and increased to 0.35 in the third year as the plants rapidly increased in size. Coefficients for the rabbiteye varieties were consistently higher during all three years, reaching 0.5 in the third year.

Site Selection for Subsurface Drip Irrigation Systems in the Humid Region

Site selection for subsurface drip irrigation (SDI) in the humid region must be carefully considered to ensure optimum system performance and crop yield while minimizing unnecessary expenses. SDI has been shown to result in similar or higher crop yields on many crops while reducing water use. However, characteristics of the field, soil, crop, cropping system, water resource available, managerial and farm labor resources, economic factors, and industry support infrastructure affect decisions about the appropriateness of SDI in a given situation. These topics are discussed with emphasis on their effect on the humid regions of the United States.

NEW IRRIGATION-PLANT PRODUCTION SYSTEM FOR WATER CONSERVATION IN ORNAMENTAL NURSERIES: QUANTIFICATION AND EVALUATION OF IRRIGATION, RUNOFF, PLANT BIOMASS, AND IRRIGATION EFFICIENCIES

A new irrigation/plant production system, Multi-Pot Box System (MPBS), was field-evaluated during the two growing seasons (summer and fall, 2001) for efficient use of irrigation and rainfall for container nursery plant production. The system was compared to the conventional system (CS) irrigated with overhead sprinklers. Viburnum odoratissimum (Ker-Gawl.) was grown as a test plant. The following treatments were imposed: (i) three white color MPBSs with side-mount water level switches installed at 0.01, 0.02, and 0.03 m from the bottom of the system reservoir, (ii) three black color MPBSs with level switches installed at the same depths as in the white MPBSs, and (iii) control (CS). The level switches controlled the water levels at pre-determined levels and triggered irrigations automatically at these threshold levels. The white and black MPBSs were very effective in increasing irrigation water use efficiencies (IWUE), rainfall harvesting, and plant biomass production as compared to the CS. For example, in the summer season, only about 30% of the plant water use in the MPBSs was supplied by irrigation water, thus, reducing irrigation requirements and resulting in high IWUE. The color of the MPBS had a significant effect on plant growth but no significant effect on irrigation demand or runoff. The water use efficiencies and plant biomass production of the white MPBS were significantly greater (p < 0.05) as compared to the black MPBS. The efficiencies and plant biomass production of the black MPBS were significantly greater than the CS. In the fall, the white and black MPBS with level switches installed at 0.01 m resulted in the lowest irrigation demands. In the summer, about half of the total rainfall (320 mm) was captured in the reservoir of the MPBSs. In the fall season, approximately 30% of the total rainfall (90 mm) was captured in both systems and later used by plants. At least 92% and 76% of water savings, relative to the CS, were achieved by using the white MPBS in the summer and fall, respectively. Results suggested that under these experimental and similar climatic conditions, the white MPBS is superior to the black MPBS and CS. The white MPBS presents a potential opportunity for an efficient irrigation and significant water savings for container-grown nurseries.

Evaluation of Soil Moisture Sensors, and Their Use to Control Irrigation Systems for Containers in the Nursery Industry

Water savings are important from an economical and environmental point of view. The nursery industry accounts for a large amount of the water used for agricultural purposes. The high porosity of substrates used to grow plants in containers affects the precision of moisture sensors, hence the need to evaluate their efficacy in this type of growing media. This paper describes studies that use time domain reflectometry (TDR) and tensiometers as soil moisture sensors in conjunction with a computer controlled irrigation system. Both sensors have their advantages and disadvantages, however, compared against a common timer-controlled system the TDR system accounted for water savings above 60%, and with the tensiometers the savings were around 50%.

Crop Water Requirements of Mature Southern Highbush Blueberries

Measures of crop water use for mature blueberry plantings could offer improved irrigation management by growers, reducing irrigation diversions. The objective of this research was to provide crop coefficients for mature southern highbush blueberry plants. Measures of crop water requirements were made using a water balance enabled by suction lysimeters. Eight established, mature plants were instrumented for water balance. Irrigation was managed to ensure well-watered conditions. Monthly crop coefficients ranged from 0.59 to 1.10 with an annual mean of 0.84.

CRITICAL MANAGEMENT ISSUES WHEN USING SDI IN HUMID AREAS

Proper irrigation scheduling, system maintenance and chemigation is imperative to the successful implementation of SDI (Subsurface Drip Irrigation). Because working components of an SDI system are underground, it is important to establish baseline operational performance standards while the system is relatively new. Future declines in operating performance can often be diagnosed by comparing real time performance with baseline criteria. Irrigation scheduling is the process of determining when and how much water to apply. Weather, crop models, and various soil and/or plant sensors can be used to determine when to irrigate and a water balance can be used to decide how much water should be applied. Very small amounts of water can be applied on demand through SDI to increase water application efficiency. SDI can be used to efficiently apply chemicals such as pesticides and crop nutrients. These systems can deliver frequent fertilizer applications at low concentrations, resulting in increased nutrient use efficiency and lower cost per unit of harvested product. Chemical application through the lines is also used for protection of the tubing from rodents, insects, and obstructions cause by root intrusion or mineral precipitates.

Dew Point Hygrometers for Irrigation Scheduling in Fine-Textured Soils

The competition for water in irrigated agriculture with other water users has increased demand for accurate determination of soil water status for efficient irrigation. There has been much interest in measuring topsoil hydraulic properties, including soil matric potential (SMP), as a tool for irrigation scheduling. Currently, many methods are available to measure SMP, including tensiometers, electrical resistance units, heat dissipation, and filter paper techniques. However, their acceptance is limited because of limitations in different applications (i.e., soil type, measurement range, accuracy, etc.). Soil hygrometers may be better-suited instruments to measure SMP when they are used in fine-textured soils (i.e., clay). The objectives of this experiment were: (1) to determine the mean SMP in topsoil (0-0.30 m) at the onset of irrigation, resulting in maximum corn (Zea mays> L.) grain yield using the dew point soil hygrometer; (2) to relate these SMP values to the full profile (0-0.90 m) available water (AW) to determine the optimum value of SMP for scheduling irrigations for summer-grown corn under a Mediterranean climate; and (3) to determine the number of soil samples required for a valid representation of SMP measured with a dew point hygrometer under field conditions. An experiment with three irrigation treatments (S1, S2, and S3) was conducted on a clay soil (47% clay). Three irrigation treatments were based on replenishing the 0.90 m root zone to the field capacity when the soil water dropped to 75% (S1), 50% (S2), and 25% (S3) of available water holding capacity (AWHC). A dryland treatment (S4) was also included. The mean SMPs for topsoil at the onset of irrigation were -303, -406, and -635 kPa for S1, S2, and S3 treatments, with grain yields of 5333, 6058, and 4570 kg/ha, respectively. The dryland treatment resulted in the minimum yield of 740 kg/ha. Results showed that the mean SMP value of -406 kPa can be a reliable point to apply irrigations for corn grown in this soil. The relationship between 0-0.30 m depth SMP versus full profile (crop root zone) AW was found to be: SMP = 2150 - 4.35AW (r2 = 0.80, n = 47, SMP in kPa, AW in mm). This equation can be used to estimate full profile AW using 0-0.30 m depth SMP. For this soil and no-rainfall condition, monitoring one layer (topsoil) SMP can be used to estimate full profile AW. Results also showed that 28 ± 8 or 20 ± 5 soil samples are needed to obtain ± -10 kPa precision of SMP measurements for the maximum yielding treatment (S2) at 95% and 90% confidence levels, respectively. For these soil conditions, the dew point soil hygrometer is a well-suited device that can be used to measure SMP for irrigation scheduling. It is sensitive and consistent, and easy to calibrate and use.

Crop Water Requirements of Mature Blueberries in Florida

Climate-specific measures of crop water use of mature blueberry plantings could offer growers improved irrigation management. In contribution to improved irrigation management practices for Florida blueberry growers, this paper presents a crop coefficient for mature Southern highbush blueberry plants. Measures of crop water requirements were made using a water balance enabled by drainage lysimeters. Grower-controlled irrigation management is compared with a shorter, researchermanaged, timer-controlled schedule. A researcher-managed plot on a commercial blueberry farm is irrigated independently of the grower’s fields, enabling comparison of crop ET and beneficial evaporated fractions, the ratio of water used for crop development to the gross irrigation diversion between grower-controlled and researcher-managed timer-controlled irrigation management. Four lysimeters in the researcher-managed plot and four lysimeters in a six acre plot of the grower’s field were used to measure crop water use. Water balance durations range from 7 to 10 days. Lysimeter area corresponds closely to crop canopy area of mature plants. Irrigation inputs are measured by flowmeters, and precipitation inputs are measured by an onsite weather station that is also used to determine reference ET.

5. General system design principles

Publisher Summary Micro-irrigation systems are designed to transport water from a source through a delivery network of pipes and emission water devices to a crop. The general goal of a micro-irrigation system design is to provide irrigation water uniformly and efficiently to a crop to help meet the evapo-transpiration needs and to maintain a favorable root zone water balance. Associated goals are to increase fruit or fiber production or to maintain plant visual quality. Other water delivery goals may be to protect plants and/or fruits and flowers from extreme temperature conditions (hot or cold), to apply crop or soil chemicals (fertilizers, pesticides, etc.), or to dispose wastewater, which can be an important resource. Thus, the ultimate design will vary from one system to another. System goals need to be established with defined objectives, system constraints, and a desired set of outcomes to be used as a common theme throughout the design process. This will help with the selection and placement of specific components, sizing, and layout of the distribution system, and the development of appropriate operational guidelines and procedures. In this chapter, most of the discussion is focused on the design processes specifically related to micro-irrigation systems in terms of sources of water, system hydraulics, and micro-irrigation components.