Maximize Your Potato Crop’s Growth Potential with Rivulis Irrigation System
A World of Potential
With tens of millions of hectares under cultivation around the globe, the potato is one of the world’s largest and most important crops. But not all production is equal nor effective. Drip irrigation is a key lever to improving yield.
The world average is 20 t/ha1 , the average production in Germany is 42.7 t/ha2 , and in New Zealand the average yield is 50 t/ha3 . As such, for much of the world, there is opportunity for significant yield improvement that is easy to achieve. Drip irrigation can help achieve these yields.
Growing Potatoes to Meet Market Requirements
For most regions, there is no such thing as just growing ‘general potatoes’. From the onset, a growing program needs to be developed in order for the potatoes to meet the strict market requirements for their final use. Market guidelines for potato quality are becoming stricter, resulting in reduced profit and sometimes complete rejection of crops that do not meet the market specifications. In this brochure, we share how drip irrigation can help you grow the right potatoes for each market need. pattern to the ground.
Applying Just the Right Amount of Water
Potatoes have a water requirement that can reach up to 25 mm/week during bulking. At the same time, they are very sensitive to both under and over irrigation that can damage the plants and in turn, the tubers. There are two reasons for this sensitivity: 1. Potatoes have a very shallow root system that prevents them from reaching deeper nutrients and water 2. The tubers are very susceptible to damage during the growth stage and from disease
Accurate water management is critical to achieve the best yields and drip irrigation makes it possible to keep the soil moisture level close to Field Capacity through frequent but small irrigation applications.
Not All Irrigation is Created Equal
It is well established that potatoes have a very high sensitivity to water. However, just using any type of irrigation throughout the field will not solve the problem, even if on paper, it meets the crop water needs. If the irrigation itself is not uniform, you can create variability across the field which causes the crop damage
The Wind Factor
Potatoes are often grown in windy conditions and a major downfall of using sprinklers for irrigation is that they do not perform well in wind. Some sprinklers can deliver high ‘published’ uniformity; however, these tests are performed in labs, not in the field. As the graph on the next page demonstrates, sprinkler uniformity drops quickly as wind speed increases. This reduced uniformity leads to some plants receiving too much water, and others receiving too little.
Accurately Apply Chemigation with Drip
Application of N, P, K, Ca, Mg, S, B, Mn and Zn have a direct impact on yield, tuber size, tuber number, dry matter, internal structure, skin, storage potential, cooking potential, and tuber strength. To produce a crop that is ‘in-spec’ for its final market, you need to get all these nutrients right using the right amount at the right time and at the right location. Too much nitrogen for example, and you increase your foliage while decreasing dry matter and starch. One of the major benefits of drip irrigation is the ability to apply chemigation (fertilizer, herbicides, insecticides and fungicides) accurately and effectively by injecting it into the irrigation system itself. Fertilizer, insecticides and fungicides are easily applied directly to the root zone with over 90% uniformity, without manual labor or tractor use. Sprinklers do not provide this flexibility or accuracy and you need a tractor to apply the nutrients, which requires more resources (fuel, equipment and labor) and is less efficient as nutrients are lost. Additionally, sprinklers increase humidity and increase the risk of black leg disease. Sprinklers also irrigate the interrows so that additional weed control is required, and foliage is wet increasing the risk of late blight and target spot. Worse yet, sprinklers wash off the fungicide that has been applied so you are not protecting your plants completely, while wasting valuable fungicide that runs off into the soil.
Choosing the Right Drip System
Processed (crisping, french fries and canning) have different needs, and therefore different irrigation recommendations compared to potatoes grown for the fresh market. Single Row Drip System When growing for the fresh produce market, quality and consistency is key. For this reason, it is recommended to have one drip line/tape per row of potatoes for all fresh market crops. A single row drip system is also recommended for processed market potatoes in many applications. Typical Installation: 90 cm centers 1 drip line/tape line per row Thin wall drip line/tape (4 – 8 mil depending on environmental conditions) 15 – 30 cm dripper spacing with 1 lph flow per dripper depending on spacing. Goal is approximately 3 lph per meter. Slow application of water is beneficial as it helps keep the soil soft, especially on clay where skin damage during harvest is a risk. Install drip lateral above the seed and bury with 2 – 5 cm of soil It is best to install at the same time as planting to avoid damaging the new shootings from the seed. Tips: Common scab is a major challenge with fresh market potatoes. To minimize this, you need to keep the moisture level sufficient through tuber initiation and just after “hook” stage. After this stage, you can revert to more supplementary irrigation scheduling. As the season progresses and more ridging is made, the depth of your drip line/tape can be up to 20 cm by the end of the season. When the drip line/tape is this deep, there is much greater distance for the water to reach the surface. Therefore, do not rely on seeing a wetting pattern. If you rely on seeing it, you run the risk of over irrigating. Instead, moisture can be measured quickly and economically with a basic tensiometer.
Interrow Drip System
For processed markets, there is more flexibility in systems to choose from. It is possible to use one drip line/tape per row of potatoes, or you can also use a re-usable pressure compensated system with a drip line installed every two rows. Typical Installation: 160 cm centers 1 drip line per 2 rows of potatoes distanced 80 cm apart Drip line is placed in the shallows of the ridges Heavy wall (above 30 mil wall thickness) PC drip line is used Heavy wall allows for multi-season reuse PC drip line provides accurate flow over wide pressure ranges (sloping round and long-run lengths) 30 cm dripper spacing with 1 lph dripper Shallow burial of the drip line is recommended Tips: This system is excellent for leased land as it is portable and flexible for a wide range of other configurations. It is not recommended for saline water. As potatoes are sensitive to salinity, it is better to use a 1 drip line/ tape per row system as this will ‘push’ the salt residue away from the roots and leach into the soil. Avoid having dripper spacing of more than 30 cm as this can result in tuber bunching around the outlets of the drippers, resulting in inconsistent tube size.
D5000 Flow x Pressure: Uniform flow over a wide range of pressures
Find the Right Rivulis Drip Line or Tape
There are three common drip irrigation systems that you can install based upon your needs