Benefits

Commercial growers can benefit from drip irrigation and still work within a tight budget. Drip irrigation saves up to 50% water compared to sprinkler systems. Drip irrigation delivers water to the roots and avoids problems associated with wet leaves. Drip can eliminate problems with runoff, saturated soils and uneven coverage. Drip irrigation systems can be scaled to any size operation. In other words, the expense of drip irrigation is easily offset by the twin benefits of healthy plants and time saved.

Small-scale commercial growers can benefit from a drip irrigation system that is inexpensive, simple to install and easy to maintain. The following MarketGro 1500 system is a typical small commercial drip system. The system can be easily expanded.

Plant Spacing

What do you want to irrigate? The MarketGro 1500 System will deliver up to 1500 gallons per hour to drip irrigate row crops, nursery stock, orchards, vineyards or any other crop planted in rows. Plant spacing can be from 5" up to 10' or more. The amount of water delivered per hour per dripper can range from 1/2 gallon to 2 gallons. Drippers can also be grouped to deliver even more water per hour to large trees.

Capacity

Our MarketGro 1500 drip irrigation system has enough capacity to drip irrigate 2500' of narrow rows with DL6 thinwall dripline at one time or 3000' of rows using DL4 heavywall dripline at one time. If T2 blank tubing is used in the row and 1 gallon per hour drippers are installed on 6' centres, the system can serve up to 9000' of row. The system can also be expanded to adjacent crop areas. (see Figure 3)

Requirements

Water pressure of 40 to 60 psi at the water source is ideal and is the common working pressure range for many pumps and municipal water works.

Water flow must be a minimum of 11 gallons per minute (660 gallons per hour) for filter and regulator to work properly. (See Drip Irrigation for a Market Garden for smaller capacity systems)

We are relying on a disc filter so organic material in the source water should be less than 5 mg/L. Inorganic material should be less than 10 mg/L. Otherwise a more sophisticated and expensive filtration system is needed.

Figure 1 - Basic Single Field Layout - click to Zoom

Figure 2 - Basic Mid-field Layout to serve longer row length - click to Zoom

Main Supply Tubing

We have to plan the lengths of supply tubing and rows to make sure that the MarketGro drip irrigation system will operate correctly.

The MarketGro 1500 system is based on using 1-1/2" inside diameter Series 75 polyethylene tubing to move up to 1500 gallons per hour from the water source to the edge of the irrigated field or orchard. 1-1/2" polyethylene (PE) Series 75 heavywall tubing is readily available from any local plumbing shop in large coils. Small quantities of 1-1/2" Series 75 PE tubing are very expensive to ship so at Northern Garden Supply, we stock all the hard-to-find parts that you add to your locally obtained 1-1/2" tubing to make an efficient MarketGro drip irrigation system.

1-1/2" tubing will lose about 2 psi of water pressure for every 100' of length at 1500 gallons per hour due to friction. So it's best to keep the length of the supply tubing to a reasonable length. 300' of 1-1/2" diameter tubing will lose 6 psi, so if we start with 45 psi at the source, we will end up with 39 psi at the crop area 300' away. It's best to have more pressure at the start of the drip system than you need. The MarketGro 1500 drip system will operate best at 12 to 15 psi which is determined by the pressure regulator.

Row Length

There are practical limits to the length of rows as well. For instance if you wish to use DL4 Heavywall Dripline, the maximum row length should be 250'. If you wish to use regular T2 1/2" tubing and punch in drippers where they are needed, the rows maximum length should also be 250'. If you are using DL6 Thinwall Dripline, rows can be up to 325' in length. If you have rows 500' long, you could install the header at a right angle across the middle of the rows so that each length of tubing needs to be only 250' in length. (See figure 2)

We can keep adding rows until the amount of water delivered approaches 1500 gallons per hour. For example, you can have 15 rows 200' in length if you are using DL4 Heavywall Dripline for a total of 3000' of rows.

If you have more than 3000' of rows to irrigate, you can install a Tee fitting and two valves along with a second header. You then use the valves to divert the water to the second header. Only one header can be in operation at one time but your pump or source can supply many separate headers each serving 3000' of row.

Figure 3 - Double-field Layout - system can be expanded to serve more than one field - Click to Zoom

Design Principles for MarketGro 1500 systems

• Approximate friction loss for 1-1/2” Series 75 PE tubing is:

2 psi per 100’ at 25 gallons per minute (1500 gallons per hour) or
1.3 psi per 100’ at 20 gallons per minute (1200 gallons per hour)

• Friction loss for fittings will add 20% to the tubing loss.

• Pump or water source should be as close to the crop area as possible to minimize friction losses.

• Filter and pressure regulator should be located as close to the crop area as possible.

• Row assembly (header) length with 10 to 15 outlets should be short enough (<300’) to keep total friction pressure loss to no more than 3 psi if using a pressure regulator rated at 15 psi.

• Row assembly (header) should bisect rows if rows are longer than the maximum recommended row length but less than double the recommended length.

• MarketGro systems are designed for level crop areas with less than a 2% slope, which is less than 5’ elevation change in 250’ of row length.

• Row assembly (header) should be located along the height of land if the crop area has a slope so that gravity will help overcome friction losses.