SALTIER WATER CALLS FOR SPECIFIC MEASURES SALINITY IN SURFACE WATER AND GROUNDWATER IS INCREASING IN MANY REGIONS. THIS HAS A MAJOR IMPACT ON SENSITIVE CROPS LIKE CARROTS. GROWING ADVISOR SANDER BERNAERTS RECOMMENDS GROWERS REGULARLY MEASURE EC AND TAKE STEPS TO MAKE SOIL LESS DEPENDENT ON IRRIGATION.
An ongoing rainfall deficit and intensive irrigation are causing salinization of groundwater and surface water. We can see this in high and rising EC levels. In parts of the Dutch province of Flevoland, for example, the water has become unfit for irrigation, says the independent growing advisor Sander Bernaerts. “For a crop like carrots the EC of the irrigation water can’t be above 1.0.” The same is true for seed-grown onions, lettuce, clover, peas and beans. Other crops are sensitive too. For red beetroot and spinach, the threshold is about 2.0; for onion sets, it’s 2.5. Potatoes, celery root, cabbage and grains have a higher tolerance. The EC of the water isn’t a problem in itself; the issue is its effects on the root zone. “After irrigation with salty water, the soil EC shoots up,” Bernaerts says. “I’ve seen examples of onions being irrigated at EC of 1.6, which caused the soil EC to rise to 1,200mS. In onions and carrots I’ve measured soil EC above 1,500mS. For sensitive crops like these, 700mS is the upper limit.”
Water and nutrient absorption
Bernaerts advises growers to regularly measure the EC of the water and soil. Variation between fields, water channels and sources is significant, and values often go up as the season goes on. “An EC meter is a small investment that can be very valuable,” he says. “The water quality often seems fine in early spring, but intensive irrigation can sometimes cause
“For a crop like carrots the EC of the irrigation water can’t be above 1.0..”
it to get saltier by the week.” High soil salinity values Sander Bernaerts threaten yields and quality. Salt impedes the roots’ uptake of water and essential minerals. In many cases, the damage is greater than the grower realizes. Often, the crop will come up but the seedlings will soon dry out. Or the plant will appear to take root but grow slowly.
Soil retention
What’s a grower to do? First of all, dose fertilizers carefully. All of them will raise the EC of the soil. Bernaerts also advocates using cultivation techniques that help the soil to better retain the water that’s present. This will reduce plants’ dependence on irrigation. In general, this means paying more attention to soil structure. For carrots specifically, in heavy soil, he advises intensive use of an over-the-top rotary tiller to create a fine seed bed. Timing can also make a big difference. For example, starting soil preparation early means spring showers could fall on the ridges and aid the germinating plants. Finally, Bernaerts also advises staying attentive to seeding conditions. It can pay off to seize an early opportunity, or to wait a bit longer.
BEJO CARROT MAGAZINE
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