Increasing Grassland Yield

Grassland Yield

The main yield components of grassland and pasture are shoots per unit area, and dry matter content. Higher yields come from optimising leaf and shoot numbers, maintaining a green leaf canopy and achieving a high dry matter content. A balanced crop nutrition program including all macro and micronutrients is essential to help manage all of these components.

Macronutrient Uptake by Grassland 

Nitrogen is the crucial nutrient for influencing grassland yield. Requirements for potassium, phosphate, sulphur, calcium, and magnesium are related to the amount of applied nitrogen. There is a large demand for these macronutrients during early spring growth and to avoid limiting yield it is critical that sufficient quantities of nutrients are available for uptake when required by the plant. The nutrient uptake and offtake from grassland depends on the intensity of production and whether it is mowed or grazed.

Macronutrient Uptake

This table shows how the macronutrient offtake per tonne dry matter varies with yield and depending on whether it is grazed or mown.

Micronutrient Uptake by Grassland

A balanced crop nutrition strategy is essential and although much lower amounts are needed the correct balance of micronutrients should be available since these are essential elements for achieving high yields. The most important micronutrient on grassland yield are copper, manganese and zinc. 

Other micronutrients which are not essential for grass but are required by grazing animals include sodium and selenium and also copper and zinc are required in higher levels in animals than are required for grass growth.

Micronutrient Uptake

This table based on studies in the UK shows the wide variation in micronutrient uptake per ha depending on the management system.

Crop Nutrition and Grassland Yield

Nitrogen

Nitrogen is the major nutrient required by grass. It is the key to achieving high dry matter yields and is often strategically used to increase production as it is needed. The key to achieving high yields is to apply the correct amount of nitrogen, from the right source at the right time.

Phosphorus

Phosphorus plays a role in many plant metabolic processes and enzyme activities, so even though phosphorus demand is low compared to that of nitrogen its availability is essential. Phosphorus accelerates and improves grass growth and is important for increasing yield. The older the sward, the more important is phosphorus fertilization. Phosphorus is very immobile in soil and its availability is limited by pH, by distance from plant roots and soil temperature.

Potassium

Potassium is the nutrient taken up in the greatest quantity by grassland swards. Potassium has a wide-ranging role in the plant affecting nutrient uptake, photosynthesis, rate of growth and feed value.

Sulphur and Magnesium

Sulphur is essential in the formation of protein and so is crucial for growth and development. As grass grows both sulphur and nitrogen are used together so sulphur deficiency will decrease nitrogen use efficiency and so reduce yield. Historically sulphur was supplied by atmospheric deposition however as a result of reduced industrial emissions and improved air quality this has become much lower in recent years so increased responses to sulphur is now seen in grass and other crops.

Magnesium also needs to be considered. Magnesium is an essential nutrient, and in situations where magnesium is deficient, there will be a significant reduction in grassland yield.

Micronutrients

Zinc and manganese have also been proven to have effects on grassland yield.

Other Crop Management Practices Influencing Grassland Yield

  • Maintaining the correct soil pH
  • Maintaining good soil structure and minimising soil compaction 
  • Improving and maintaining soil drainage 
  • Maintaining a high proportion of desired species within the sward to maximises nutritional value and yield
  • Regularly reseeding and/or oversowing to maintain high quality swards across the farm and selecting varieties for quality as well as yield.
  • Topping to remove course material and harrowing to remove dead matter and open the sward, both of which will encourage tillering.
  • Managing grazing effectively to avoid damage and minimise rejection.