Corn Grower Has Influence On The Nitrogen Soil Surplus, But Soil Type And Groundwater Level Are Fixed

For corn growers, the type of soil and the level of the groundwater mainly determine how much nitrate remains in the soil and how much nitrate ends up in the surface and groundwater. The use of manure and the cultivation of green manure have a lesser influence on the amount of nitrate in the soil. This is evident from research by Wageningen Economic Research commissioned by the Ministry of Agriculture, Nature and Food Quality. Researchers looked at corn cultivation on sandy soil at dairy farms.

The farmer can do nothing about the soil type and little about the groundwater level, because the location of plots is fixed. Naturally, he cannot determine the weather and the distribution of precipitation over the growing season himself. But he does have control over fertilization, irrigation and the cultivation of a green manure or catch crop to control the nitrogen soil surplus.

Nitrate above the standard for corn
The nitrate concentration on corn plots of dairy farms on sandy soil is on average above the standard of 50 mg per liter. Too much nitrate in groundwater is not good for the quality of drinking water. The nitrogen soil surplus from maize cultivation on dairy farms on sandy soil is approximately 50 kg per ha and has remained stable in the period studied 2006-2019.

Dairy farmers like to grow corn to feed it to dairy cattle in combination with fresh grass and preserved grass. It leads to a balanced protein content in the ration. The question is how to maintain or increase the yield of corn while at the same time reducing the nitrogen soil surplus and the nitrate concentration in corn.

And that is a problem because in practice the farmer no longer has many options to improve the cultivation of corn. For example, it is not wise to fertilize the corn more because it hardly produces higher yields. Moreover, this nitrogen-rich fertilization produces more surplus in the soil and (to a limited extent) a higher nitrate concentration in the leaching water. Farmers can also only irrigate to a limited extent or not at all to promote crop growth. The remaining solution is to grow a green manure or catch crop. This usually turns out to be a useful measure to increase yields and reduce the soil surplus of nitrogen and nitrate concentrations.