What We have Learned about Optimal Pasture Recovery in New Zealand
Updated: Nov 8, 2022
When I started my regenerative farming journey in 2008, I allowed my pastures to recover too long. Ian Mitchell-Innes came to my rescue in 2011 when I was applying over rest and saved my farm business. In the past fifteen years of regenerative farming and consulting I have learned:
1- The best soil Armour is a dense, diverse, green, and rapidly growing perennial pasture
(just ask Gabe Brown. I did.)
Since I farmed in a humid temperate climate, I could keep pasture green in the dry months unlike semi-arid places like Zimbabwe or Mexico where brown litter trampled on the soil is fine because it is all they have available. The context you are working in must be well understood.
2- Perennial pastures don’t need to go to seed on purpose to replenish the seed bank. Selective grazing and non-selective trampling with mob grazing allows more than enough seed from desirable species to form to replenish the seed bank. Five to ten percent of tillers going to seed is enough and if you are taking care of your perennial plants, they will be long lived by definition so why do you need so much seed?
3- Mimic nature. Do wild grazing animals ignore lush green grass and wait for it to turn brown before they graze it? Mimic nature by allowing pasture to recover long enough for the dung dropped during the previous graze to break down and not smell offensive to the stock. Natures brilliant design brings herbivores back to graze quicker in wet, kind weather such as springtime when grass is growing fast because dung breaks down fast as well. It takes more time for dung to decay in cold, hot, or dry conditions giving plants the extra time they need to recover. A holistic grazing plan helps farmers achieve the optimal recovery for their pasture all the time because it adapts to the ever changing weather.
4- Are long pasture recoveries good for the soil? Plants pump the most liquid carbon into the soil through their roots WHEN THEY ARE VEGETATIVE AND GROWING RAPIDLY according to Christine Jones. This means on temperate, humid grasslands found in New Zealand, the faster you keep your grass growing, the more soil carbon you can build. I have evidence from my farm (with 800-1000 mm of annual rainfall) that mob grazing pastures just at the end of the fast blaze of growth can lift soil organic matter at least 0.3% per year over ten years. I believe this occurred because the liquid carbon pathway is 2-13 times more efficient at creating long term soil carbon than litter. (Sokol, et al., 2018). If anyone has lifted soil organic matter quicker, please share with me how you did it.
5- If pasture recovery is too long, you will grow less grass. One of my sheep and beef clients in South Canterbury started her regenerative farming journey on a 90 day round in winter because that is what the neighbours did. We noticed if we were not decking the pastures, they recovered to our target four leaf stage of cocksfoot (orchard grass) in 75 days over winter June through August. The following year we set the winter target recovery for the grazing plan at 75 to 85 days and grew more pasture than she knew what to do with by September and some of the cattle had gained 2 kgs/day.
Broughams found out back in 1956 that some New Zealand farmers were missing out on potential pasture production by letting pasture over recover in the winter. They shut up pasture for winter April first in the central North Island. On one 126-day round, they grew 2,377 kgs Dm/Ha but on two 63 day rounds they grew 3,688 Kgs/Ha. They observed that grass growth curve flat lined after 60 days. (Langers, RHM., Pastures and Pasture Plants. 1973)
6- Over recovery slows nutrient cycling. On the highly productive ancient grasslands, rich diversity and an abundance of primary producing plants were maintained by teeming herds of grazing animals and their associated predators who collectively acted to cycle nutrients rapidly. I believe it was the power of animal impact which supercharged nutrient cycling and allowed the mammoth savanna to support many more animals than expected. Zimov et al. (2012) extrapolated high productivity from fossil records concluding “based on animal skeleton density in frozen soils of northern Siberia, mammoth-steppe animal biomass and plant productivity, even in these coldest and driest of the planet's grasslands were close to those of an African savanna”. How could this be?
Ocean productivity is a profound example to help us appreciate the power of rapid nutrient cycling. On land 450 gigatonnes of carbon (Gt C) in plant biomass, the primary producers, feed 20 Gt C of consumers such as animals and bacteria. The oceans on the other hand have an inverted food pyramid where only 1 Gt C of photosynthesizing plants and algae support 5 Gt C of consumers such as fish, mammals, and crustations. How is this possible? Rapid nutrient cycling of the photosynthesizing plankton and algae! Phytoplankton are very productive because the turnover is high. The same principle applies if you use a grazing plan to grow your pasture faster. Higher turnover and optimizing the rate of growth is the ticket to high productivity. Over recovery makes your farm less productive because your pastures grow slower and remember slow growing pasture feeds the soil less liquid carbon.
7- Optimal recovery
Context must inform the recovery you set depending on what you want to achieve, the time of year, the weather, what grows in your pasture, and the class of stock you run. Therefore the holistic grazing plan is so useful because it helps organize all this complexity.
8- My dairy clients have found recovery times to achieve the three-leaf stage of perennial ryegrass (prg) their first year, especially in the summer, can grow more grass. Even though NZ research says grazing at the three-leaf stage instead of the two-leaf stage can grow 1.1 more tonnes of DM/Ha, few farmers achieve it. Some of my clients in Canterbury cut their nitrogen fertilizer in half and grew 900 more kgs/HA their first year simply by achieving three new pointy leaves on their prg instead of the usual 2.5 leaves and leaving an 1800 Kg residual instead of 1700 or less. Grass grows much faster between the two and three leaf stage than is does between the one and two leaf stage. It is hard to nail the optimal recovery without a grazing plan especially in the summer. I recommend clients lift recovery by one half of a leaf stage per year to maintain quality while they regenerate their land. This allows everyone involved to adjust. (grass, cows, microbes, and people). It is low risk and will result in pasture diversity over time even of no new seed is sown.
9- My sheep and beef clients like Jason Southerland, Farm manager at Tinwald Farm, grew heavier lambs than the year before by setting their grazing plan rotation cruise control to the time it takes to get to two leaves of PRG until weaning. They had one mob of 1800 mixed age ewes with lambs eating selectively followed by 300 or so cattle in the paddock behind to selectively eat and non-selectively trample uneaten grass so it freshened up green. They shifted to a fresh paddock up to three times a day. Although only achieving two leaves it is a compromise for plant growth, it allows lambs to grow faster so more get away sooner. This is where understanding the context needs to be accounted for. To avoid shifting the whole paddock to brown top and dogstail with this continued overgrazing, it is important to achieve at least the three-leaf stage of recovery for prg or four-leaf stage of cocksfoot all summer on that block post weaning and send the lambs somewhere else or run them in front of a mob on maintenance. This allows plants which perform in dry weather to persist like cocksfoot, red clover, timothy, and lotus, and lucerne. He achieved the pasture quality you see below in a very dry February with no topping. They use irrigation in Central Otago.
Sokol, N.W., Kuebbing, S.E., Karlsen-Ayala, E. and Bradford, M.A. (2019), Evidence for the primacy of living root inputs, not root or shoot litter, in forming soil organic carbon. New Phytol, 221: 233-246. https://doi.org/10.1111/nph.15361
Zimov, S. A., Zimov, N. S., Tikhonov, A. N., & Chapin, F. S. (2012). Mammoth steppe: A high-productivity phenomenon. Quaternary Science Reviews, 57, 26–45. https://doi.org/10.1016/j.quascirev.2012.10.005