Photo by Gregory Heath, CSIRO on Wikimedia Commons

Lucerne has long been called the king of fodder crops because of its high protein content and nutritious hay1. Lucerne belongs to the leguminous family which contains all plants that have the ability to fix nitrogen from the atmosphere and deposits it directly to plant roots. These special plants are able to do this through the rhizobium bacteria which live inside the root nodules. Pasture that has legumes, specifically lucerne, in the mixture normally require very little or no nitrogen fertiliser as lucerne can fix up to 284 kg N/ha/year2.

                                                                           

Lucerne root nodules where N fixation takes place.

Lucerne has a very vigorous root system. As a result, it is able to scavenge the soil for water and nutrients, a characteristic which becomes handy during drought periods. This ability to move through deep layers makes it a good pasture to plant in dryland conditions. However, for lucerne to thrive, the soil health needs to be in a certain state. Below are some basic soil requirements for growing lucerne:

Good soil drainage

Soils that are underwater for long periods during the year can cause diseases to develop in seedlings. It is paramount that lucerne is planted in soils that do not experience waterlogging. Poorly drained soils will also reduce the amount of oxygen in the soil. This will cause respiratory problems for the microbes that are responsible for N fixation in the root thereby leading to a poor N fixation rate.

A well-drained soil is usually full of life. 

Crumbly soil structure indicating good soil drainage.

Optimal phosphorus levels in the soil

Lucerne utilises large amounts of P. It is therefore important that any soil phosphorus deficiencies are corrected before planting. The P is important as it stimulates root growth and is important in the flowering and seed setting processes.

High soil pH and calcium levels

Lucerne is one of the few crops which grow well on a soil with a high pH. Along with a high pH, adequate Ca levels are also necessary for optimal growth. Applying sufficient lime to reach a pH of 7 and a Ca percentage of 70% is advised. Lucerne grown on low pH soils is at a high risk of aluminium toxicity which interferes with root development. The stunted growth of roots will limit the effectiveness of lucerne’s ability to fix nitrogen, resulting in low yields.  Correcting the soil pH is, therefore, a prerequisite for optimal growth.

When these soil conditions are met, lucerne will be able to thrive, providing nutritious fodder to cattle. Farmers that include lucerne as part of their pasture mixtures will benefit from free nitrogen both from the atmosphere and from an enhanced mineralisation rate that will be stimulated by diverse pastures. The free nitrogen will help reduce fertiliser costs and improve farm efficiency.

References

    1. Lategan K. 2014. Lucerne for beginners. Available at: https://www.farmersweekly.co.za/farm-basics/how-to-crop/lucerne-for-beginners-1/
    1. Peoples, M.; Bowman, A.; Gault, R.; Herridge, D.; McCallum, M.; McCormick, K.; Norton, R.; Rochester, I.; Scammell, G.; Schwenke, G. 2001. Factors regulating the contributions of fixed nitrogen by pasture and crop legumes to different farming systems of eastern Australia. Plant and Soil 228: 29- 41.
Portia Phohlo

Portia Phohlo

Portia is a Trace and Save researcher and has been part of the team that works on the Woodlands Dairy sustainability project for the past 4 years. She studied B.Sc in Agriculture where she majored in crop and soil science at the University of Fort Hare. She went on to do her honors and master’s degree in soil science at the University of the Free State. She is very passionate about soil health and soil microbiology and believes that applying soil health principles will rehabilitate degraded soils.

In her free time, Portia loves catching up on House of Cards and The Walking Dead series. The latter she says she finds it fascinating how a dead decomposed organic material can still be conscious, this actually breaks all rules of microbiology according to her. When she’s not watching that, she enjoys watching motivational videos from Ted, especially ones by her idols Chimamanda Ngozi Adichie and Brene Brown.
Contact Portia on any of her social media platforms or alternatively email her at portia@traceandsave.com
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