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Spring beans a sustainable and profitable crop in 2023

With current high nitrogen (N) fertiliser prices every effort is being explored to reduce fertiliser N costs while maintaining grain yields and crop margins.

Growing spring beans offers the opportunity to reduce total farm N requirements as the crop only requires phosphorus (P) and potassium (K) depending on soil fertility levels. In addition the crop is an N fixer and fixes N that remains in the soil for the following crop.  This offers a double reduction in farm N requirements at a time of high fertiliser N prices. Spring beans currently leave a very good margin due to low input costs plus the bean premium.

Break crop benefits

Spring beans are an excellent break crop and deliver many crop rotational benefits from improved soil health to weed control options.  This is a valuable crop especially in spring cereal crop rotation where alternative break crop options are limited.  Beans deliver rotational benefits such as higher grain yields in the following cereal crop, for example grain yields can increase from 0.6 to 1.5t/ha for winter and spring cereal crops.  In addition, it has a very good IPM profile, as it is a low input crop and reduces the incidence of yield robbing disease such as take-all, septoria, net blotch and rhyncosporium in preceding crops.  Crops after beans tend to be more vigorous, establish more rapidly and evenly due to the soil health and quality benefits that beans put back into the soil.

Spring beans & N Fixation

Beans are legume plants and nodules on the roots fix N from the atmosphere.  The bean root nodules are a small in field plant N production factory.  The bean plant can fix its own nitrogen during the growing season thus reducing the need to apply fertiliser N.  More importantly the crop fixes N that remains in the soil as residual N after harvesting the bean crop.  This soil N is available to the following crop and reduces there N requirement up to 35kgN/ha.  

N advice for following cereal crops

After a crop of spring beans the soil N index moves from 1 to 2 as the soil has a higher N supply.  Table 1 below shows the fertiliser advice at soil N index 2 for a range of cereal crops with typical grain yields (t/ha). For example a crop of spring barley moves from 155kg N/ha at soil N index 1 to 120kg N/ha at soil N Index 2.  This offers a 35kgN/ha saving in fertiliser N that reduces crop costs by ~ €105/ha based on current N costs.

Table 1:- Nitrogen advice (kg/ha) for Cereal Crops at Soil N Index 2
Crop Type Spring Barley Spring Wheat Winter Wheat Winter barley
Grain yield (t/ha)* 7.5 8.5 11 10
N Advice (kg/ha) 120 150 220 185
*Adjust N rates by 20kgN/ha for each 1t/ha increase / decrease in grain yield

Soil health benefits

Planting a different crop species such as beans brings many soil health benefits to the crop rotation due to a different root architecture, plant exudates, grown habit etc...  In addition, crop haulms tend to be chopped and incorporated back into the soil, which adds valuable soil organic matter / carbon.  This provides a food source to feed soil biology and improve nutrient recycling and N efficiency in our soils.  I addition it adds to soil structure improvements and soil health over time.

Now is a good time to consider beans to help reduce farm production costs while adding many benefits to both the crop rotation and the soils on your farm for the years ahead.