Anthony Kerhervé, a farmer in Saint-Nolff in Morbihan, has decided to repeat his experiment with intercropping corn and lablab beans on 4 hectares this year. He had already tested this combination on 2 hectares two years ago. His main goal is clear: to enrich the silage with protein in order to reduce purchases of soybean meal on his farm, which produces 635,000 liters of milk and covers 142 hectares of arable land.
Lablab is a legume that, when planted alongside corn, provides an additional source of protein in the animals’ diet. This practice aims to increase the farm’s self-sufficiency in protein and reduce costs associated with purchasing feed supplements.
Traditionally, when planting corn and lablab, the seeds are mixed and then sown in the same row. However, this method can result in an uneven distribution of plants, sometimes with two or three consecutive corn plants before a lablab plant appears. To address this issue, Anthony Kerhervé opted for a Pöttinger Aerosem multi-purpose pneumatic seed drill. This seed drill has three hoppers: the two outer hoppers are reserved for corn seeds, while the central hopper, usually used for starter fertilizer, is dedicated to lablab seeds.
Jérémy Bonte, technical development manager at the seed company Semental, explains that this method allows lablab to be sown on either side of the corn row. This more even distribution across the field provides a reassuring visual effect for the farmer and promotes better growth of both crops. Anthony Kerhervé sowed 100,000 corn seeds per hectare and 80,000 lablab seeds per hectare.
To ensure the success of this intercropping system, it is recommended to wait until around May 10 to sow the corn-legume mixture. It is also necessary to adjust the weed control program, as farmers are limited to using only two or three active ingredients. This crop is compatible with hoeing, which allows for mechanical weed control.
The corn and the lablab sprout at the same time, but the corn quickly takes over. Toward the end of July, the lablab naturally finds a corn plant to use as a support, without competing with it. Jérémy Bonte notes that by planting the lablab near the row of corn, it quickly finds something to climb on. By the end of August, the corn and the lablab reach the same height.
The additional cost of this intercropping system is estimated at between 100 and 110 euros per hectare compared to conventional corn cultivation. However, with a yield of 14 to 15 tons of dry matter per hectare, a gain of just 0.7 points in total nitrogen content (TNC) is sufficient to offset this additional cost, based on a soybean meal price of 450 euros per ton. On average, lablab yields an increase of between 1.5 and 3 points of TNM. In addition to the protein enrichment, this intercropping improves silage digestibility and provides more fiber.
Research is currently being conducted by INRA, the Chamber of Agriculture, and Arvalis to bring to market a seed inoculant for lablab beans. This inoculant would enable the legume to develop root nodules, giving it the ability to fix nitrogen from the air and make it available to the surrounding crop.
Jérémy Bonte points out that this innovation offers two key benefits: reducing nitrogen fertilization and increasing the protein content or total nitrogen content in corn silage. This approach is part of a sustainable agriculture strategy aimed at reducing inputs while improving the nutritional quality of forage.
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