PLANNING PHASE

“ A row crop drip system does not make a farming operation good. On the contrary, one needs to START with a farming operation and then adopt row crop drip irrigation and properly adjust farming practices ( and implements) around the new irrigation methods to ensure success.” - ITRC

Planning and Design considerations Type of system Water quality/quantity Clogging/Filter system Fertilizing/Chemical injection Soil moisture distribution Layout/Emitter application/Germination Distribution lines/zones Miscellaneous control devices Costs Maintenance Automation

Type of System Max Slope Max soil intake rate (in/hr) Shape of field Adaptable toSown, drilled, sodded crops Labor (hr/ac) Cost ($/ac) Orchards/ vineyards Row crops Drip Point-sourceNo limit Any YesNo Line-sourceNo limit Any Yes*YesNo Subsurface51.5AnyYes*Yes Bubbler53AnyYesNo SprayNo limit any YesNoNo** * Can be made to work** Will work for low cover crops

Water quality Water quality is usually the most important consideration when determining whether a micro irrigation system is physically feasible.

Water quantity Crop ET MAD/stress – Root zone Salt Tolerance – leaching requirement Frost control Germination

System capacity. ◦ ….shall be adequate to meet the intended water demands during the peak use period ◦ ….shall include an allowance for reasonable water losses (evaporation, runoff, and deep percolation) during application periods. ◦ …shall have the capacity to apply a specified amount of water to the design area within the net operation period.

System capacity Continued ◦ should have a minimum design capacity sufficient to deliver the peak daily irrigation water requirements in 90% of the time available, but not to exceed 22 hours of operation per day.

ET for Trees Big tress need more water than small trees Mature tress on close spacing need same amount of water per acre as large trees on wider spacing If there is several blocks of the same type of tree using the same flow rate per tree, but on different spacing. Each block needs to be design for a different number of hours per week.

Cover crop come in all sizes shapes and types and may have an additional ET component – upwards % For cover crop grown all season long, the micro/drip system needs to be a microspray that wets a large percentage of the surface area

To crop or not to cover crop?

Drip systems – ◦ the ground surface is moist almost all the time which increase evaporation ◦ The small frequent irrigations contribute to little or no plant stress These two factors may increase the ET by as much 15% above published rates.

Considerations on Published ET Loam or heavier textured soil with at least 60% wetted volume ◦ Design for the peak month of a normal year Situations of low soil water capacity ◦ Design flow rates may need to be % higher Low water holding capacities are caused by: ◦ Small percentage wetted area ◦ Sand or rocky soils ◦ Shallow soils ◦ Shallow root systems (e.g. avocadoes or some produce crops)

Transpiration ratios - Unavoidable losses Table Seasonal transpiration ratios for arid and humid regions with various soil textures and rooting depths. Climate zone and root depthT R 1 for indicated soil texture Very course CoarseMediumFine Arid <2.5 ft (.75 m) 2.5 to 5.0 ft ( m) >5.0 ft (1.5 m) Humid <2.5 ft (.75 m) 2.5 to 5.0 ft ( m) >5.0 ft (1.5 m) Seasonal transpiration ratios (T R ) are for drip emitters. For spray emitters add 0.05 to T R in humid climates and 0.10 in arid climates

Designing for less than Peak ET Regulated Deficit Irrigation (RDI) ◦ Wine grapes (increase sugars) ◦ Alfalfa seed ◦ Almonds (start of hull split) ◦ Tomatoes (increase solids) ◦ Regulate early growth of trees and vines ( trying to avoid spindly mature trees)

Auxiliary needs Leaching Frost protection

Leaching P rocess of applying irrigation water in excess of soil moisture depletion to flush salt from the root zone. Excess water percolates below the root zone carrying the salt with it. Types of leaching Maintenance - maintain soil salinity at a more or less constant level over time Reclamation - periodic leaching to reduce accumulated salts in the soil to an acceptable level

Frost control

Crop Data Summary

Soils Data

Water

Filter systems All water must be screened and filtered to some degree before use in a micro irrigation system. Clogging of emitters is the most difficult problem encountered in micro systems The type of filter depends on the micro system and the particulate matter in the water supply

Filters

Injection All systems should be designed with injection in mind. Chemical injection is essential for long-term sustainability of drip irrigation. Reasons for chemical injection ◦ Water treatment ◦ Emitter plugging ◦ Enhancing water infiltration into soil ◦ Fertigation ◦ Pesticides ◦ Soil pH modification

Soil Moisture distribution Micro irrigation normally wets only a part of the potential plant root zone in a soil. Distribution and extent of soil wetting should be a major consideration in the design of any micro irrigation system.

The volume of soil wetted is a function of the emitter type, emitter discharge, distance between emitters, time of set, and soil texture. ◦ Fine textured soils have low absorption rates but the water will move farther from the emitters and this reduces the number of emitters required ◦ Coarse texture or high intake soils will require more emitter to obtain the necessary wet area and higher discharge emitters. For agricultural crops, typically half to three- fourths of the potential root development should be wetted

Slope and topography

Slope Slope less than 5% any type of micro system may be used 5% or Greater subsurface and basin are generally not suited Lay lateral along contour to reduce pressure variation Steep slopes may require pressure regulators at the head of each lateral

Type of System Max Slope Max soil intake rate (in/hr) Shape of field Adaptable toSown, drilled, sodded crops Labor (hr/ac) Cost ($/ac) Orchards/ vineyards Row crops Drip Point-sourceNo limit Any YesNo Line-sourceNo limit Any Yes*YesNo Subsurface51.5AnyYes*Yes Bubbler53AnyYesNo SprayNo limit any YesNo * Can be made to work

Salinity Salts tend to concentrate at the soil surface and below the surface at the perimeter of the soil volume wetted by each emitter. Salts tend to concentrate at the soil surface and below the surface at the perimeter of the soil volume wetted by each emitter.

Hose and seed placement

Germination Germination Soil Characteristics such as texture, structure, and salinity determine upward movement. ◦ Shallow placement (8-10”) course soils work better ◦ Deep placement of hose (14-24”) fine texture soils works better ◦ Beds need to be firm sprinkler or furrow irrigation may be needed to germinate field and vegetable crops.

Layout continued Crop row spacing and orientation Bed spacing raised or ground level Plant spacing – row or individual plants Soil texture and stratification

Distribution/Zones Where is the water coming from How is the water delivered to each manifold How many zones How many zones can be water concurrently

Economics The decision to purchase an irrigation system is often based on an inadequate economic analysis. The management ability and performance of the operator are probably the most important factors in determining the feasibility of irrigation or making a change in an existing irrigation system.

If the water user is an average surface irrigation system manager, chances are he/she will be an average sprinkler or micro irrigation system manager. Automated systems typically require higher levels of management

Each NRCS employee should be aware of the economics of irrigating in the general area and be familiar with the procedure used in analyzing data to determine feasibility.