9 May 2018, 01:46PM

In recent years, two effective and efficient irrigation methods have emerged as the leading technologies - drip & centre pivots. People now associate distinct advantages and disadvantages with each. Some of these are true. Some are myths. So how do you make a decision between the two? You compare the facts. There are 5 important areas where you should pay special attention:
annual return on investment
initial investment cost
labour costs
water efficiency
Crop versatility


Comparing Drip and Pivots?

There Is No Comparison


Initial Cost

• Drip systems cost 20% to 100% more than pivots.

Management

• The 50,000 emitters on a 50-hectare drip system require considerably more dedicated management than center pivots. And that doesn’t even take into account the filter, drip lines, system controls, and higher pressure pump sets.
• The 150 sprinklers on a 50-hectare center pivot installation are easily maintained with a convenient system control.

Design

• The performance of a subsurface drip system is highly dependent on the skill and knowledge of the designer.
• Pivot installations are fairly simple to design.

Installation

• Installing a drip system is difficult. You must choose tape depth carefully for compatibility with cultivation practices to ensure the drip tape isn’t damaged.
• Pivot installation is an easy and standardized process.

Germination

• Subsurface drip systems can’t stimulate seed germination if the drip tape is placed below the root zone.
• Sprinkler heads on a pivot apply water similar to the effect you get from rain, causing seeds to germinate. In fact, pivots can easily be fitted with a dual sprinkler package — one for germination and one for irrigation. On the other hand, some drip irrigators use sprinklers just for germination.

Plugging and Leaking

• With a drip system, you must apply acid and periodically chlorinate the drip line to dissolve mineral concentration that can plug emitters. And you have to spray herbicides to kill roots that could wrap themselves around water lines.
• The above ground sprinklers on a pivot are visible at all times, so plugging and leaking aren’t a problem. An average nozzle on
a pivot is 16 times larger than a drip emitter.

Filter Maintenance

• You must constantly monitor drip system filters, then flush or change them when necessary to prevent system failure.
• Typically filtering is not required when using a pivot or linear.

Life Span

• A typical drip system has a life span of approximately 10 years.
• A typical Valley pivot has a life span of 20-plus years.

Salt Build-Up

• Drip irrigation causes salt to accumulate at the dividing line between the irrigated zone and the non-irrigated zone in the soil, so that
the soil becomes salinized over time. Eventually a sprinkler system will have to flush the accumulated salt below the crop root zone for the field to remain fertile.
• Above ground sprinklers distribute water evenly over the surface, which irrigates the crop and leaches the salts in the soil to below
the root zone.

Pests

• Rats, crickets, corn borers, and mealy worms can attack vulnerable drip tape and cause leaks. You must dedicate a lot of
time and money to combat these pests.
• Pests cannot easily damage the steel structure and spray nozzles of a center pivot.

Crop Rotation

• With a drip system, crop rotation is difficult because of the predetermined row spacing. The optimum row spacing of one crop, such
as watermelons (1.8 meters) is not ideal for a rotation crop such as cucumbers (.9 meters). Rotating cucumbers into a watermelon field will result in a loss of 50% of the yield.
• With center pivots, you can easily rotate your crops as often as necessary, or your pivot circle can be segmented with different crops.

Resale

• You have to frequently replace drip tape, which is 20-25% of the total cost of a drip system. And once removed, it has no resale
value whatsoever. In fact, removing the tape costs money.
• Even after 15 years, a Valley pivot still holds a resale value of 50% of the initial purchase price.

Environmental Impact

• Typical drip tape lasts 5 years. After that, many drip irrigators have to contact hazardous material experts for proper disposal of the used tape.
• Valley equipment is made of 100% recyclable steel.




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