Applying suitable seed mixtures, minerals, and time-controlled grazing are regenerative practices used to improve pastures, but we often overlook the decline in pasture productivity simply due to plants stopping photosynthesizing during hot, dry conditions.

Photosynthesis is the process plants use to capture solar energy and convert it into stored energy. They do this by combining carbon dioxide and water into carbohydrates.

When grasses curl up their leaves and other plants wilt, it’s a sign that they have closed the air holes (stomata) on the underside of their leaves to conserve water. Unfortunately, this also means that they cut off the supply of carbon dioxide for photosynthesis. This reduces the amount of solar energy the plant can convert into stored energy. Every time this happens, our pasture productivity declines.Image of a stomata on the underside of a leaf

Open stoma in the Epidermis of a Leaf  © bccoer

What to do in Hot, Dry Conditions

We can reduce the downtime when plants aren’t photosynthesizing using C4 plants (e.g. corn, sugar cane, millet, and sorghum). They can continue to photosynthesize for a while with closed stomata.[i]

But we can also improve pasture productivity by increasing water availability to our plants. Irrigation is the standard solution – but it doesn’t get to the root cause of the problem.

By improving our water cycle, we enhance water availability long-term and cost-effectively by increasing water infiltration and storage in our soil and reducing water loss from evaporation.[ii]

Diagram of Water cycleIn most climates, because of the improvements trees make to our water cycle, pasture grown under a well-designed open canopy will capture more solar energy and produce higher yields than grown in full sun.

  1. Trees produce shade and act as windbreaks, reducing water loss from soil and pasture through evaporation and evapotranspiration (the water released into the air as water vapour from the stomata)
  2. Trees reduce water loss from soil and vegetation by creating natural air conditioning – the cooling effect of evaporation of water from the surface of leaves and transpiration by plants
  3. Tree roots create channels for water to move down through the soil and deep roots take water further down into the soil where less gets evaporated.[iii]
  4. Reduce water loss through evaporation by providing wind protection and shade
  5. Trees store water and capture extra dew

Watch how we use trees to improve pasture on our farm

Note – Refractometers (Brix Meters) are a standard piece of equipment used for measuring dissolved sugars and solids in a liquid.

Extra Benefits Guaranteed

Improving the capacity of our soil to absorb and store water enables our soil ecosystem to provide other ecological services. These include recycling nutrients and supplying them to our plants when needed, and reducing the pest and disease issues our plants get from poorly functioning soil.[iv]

References for How to Improve Pasture – Photosynthesis

[i] C4 and CAM plants use different pathways to fix carbon. For more information see Carbon Fixation on Wikipedia.

[ii] Wendy Seabrook, 2019, Drought-Proof your Farm. Published by Learning from Nature.

[iii] Neumann R.B and Cardon, Z. G, 2012, The magnitude of hydraulic redistribution by plant roots: a review and synthesis of empirical and modeling studies. New Phytol., 194 (2012), pp. 337-352

[iv] Wendy Seabrook, 2019, Ecological Farming Handbook, Published by Learning from Nature

Front cover - How to Drought-Proof Your FarmFront cover Feed plants without Fertilisers