Corn silage impoverishes the soil. How to save yourself?

Kukurydza na kiszonkę zubaża glebę. Jak się ratować?

Straw tips the scales

Corn itself, regardless of the direction of production, is classified as a crop that negatively affects the condition of the soil and leads to soil depletion of humus. This results from sowing corn in a wide row spacing and late closing of the inter-rows by plants, which can lead to soil degradation in the inter-rows (erosion) and loss of humus. Mechanical treatments of inter-row maintenance also have a negative effect on soil organic matter (GMO/MO or SOM from the English soil organic matter ).

For this reason, maize cultivation is considered to have a negative impact on the balance of organic matter in the soil. According to the best known Eich and Kundler coefficients in Poland, maize leads to the degradation of soil organic matter in the amount of 1.12-1.22 t/ha/year. More recent data, developed by the German association VDLUFA, indicate the degradation of 560 to 1040 kg/ha/year of organic matter as a result of maize cultivation.

Importantly, the above coefficients do not differentiate between grain and silage corn. What ultimately determines the effect of corn cultivation on the balance of organic matter in the soil is the amount of straw that remains in the field after harvesting. Straw is characterized by a positive effect on the balance of soil organic matter. According to Eich and Kundler, it leads to the reproduction of 210 kg of MO/ton of DM

Here we come to the heart of the discussion on the impact of corn on soil condition. In grain technology, straw remains in the field in the vast majority of cases. A large amount of crop residue, about 12-15 tons, thanks to the positive coefficient of reproduction of organic matter, will be able to compensate for the negative impact of corn agrotechnology itself on soil humus.

Unfortunately, when silage corn is harvested, almost all of the above-ground mass disappears from the field. Only short parts of the stem and roots remain in the field. This is too little crop residue to provide an adequate amount of organic matter. If other compensatory measures are not implemented, and silage corn often returns to the site, the condition of the soil will deteriorate from year to year, and humus resources will be depleted. Soil poor in humus is, in turn, less fertile, more susceptible to drought, its structure and a number of other physical, chemical and biological properties deteriorate.

Nitrogen after legumes. When will the following crops benefit from it?

Compensate for the loss of organic matter after silage corn

In order not to be "left" with a negative balance of organic matter in the soil after harvesting silage corn, alternative sources of organic matter should be supplied to the field whenever possible. It seems quite natural that growing silage corn is automatically connected with cattle breeding on the farm, and since it is connected with cattle breeding – then with natural fertilizers. Indeed, manure and other natural fertilizers are excellent sources of organic matter. According to VDLUFA, 1 ton of manure, depending on the condition and dry matter content, is a source of 28-56 kg of organic matter. However, it is increasingly common that growing silage corn is not accompanied by animal production. Many farmers simply sell standing corn to cattle breeders. The field is then left without both crop residues and natural fertilizers.

How else can you take care of organic matter after growing corn for silage? Of course, catch crops are becoming increasingly popular. Lush and well-developed biomass can also be a source of organic matter for the soil. A very good place for a catch crop in a crop rotation is the period after harvesting the early crop that leaves the field, and before corn – the catch crop mixture then has a lot of time to develop. This year, due to the relatively early harvest of corn for silage, in many places it will be possible to sow "last minute" catch crops after corn. You can decide to sow fast-growing spring species in the catch crop, such as mustard, radish, buckwheat or phacelia. In favourable conditions (mild autumn, warm, with sufficient access to water), such a catch crop will have time to develop quite well before the frosts arrive. Another solution is to sow winter catch crops. The most popular variant is sowing rye, to which it is worth adding hairy vetch for additional benefits for the soil.

In the long term, it is worth introducing plants with a positive effect on organic matter, such as small- and large-seeded legumes, into a crop rotation with a large share of silage corn. Another interesting solution is to grow corn with undersown crops in the inter-rows. In order to make corn cultivation more friendly to soil organic matter, it is worth considering no-till cultivation. In no-till cultivation, the mineralization of soil organic matter is lower than after ploughing, and corn responds quite well to simplified cultivation, especially in strip-till technology.