Is Browntop Creeping into your Pasture?
Updated: Nov 8, 2022
Last week a friend asked why I thought browntop was creeping into her timothy/red clover paddocks. On my farm, timothy and red clover did not persist until I lifted my summer pasture recovery to 3.5 leaves of perennial ryegrass and used non-selective trampling to control quality instead of non-selective eating. Leaving enough residual so your livestock have something to trample retains moisture and shades out weedy sod forming grasses even right after the grazing event. Sod forming grasses like browntop will want to spread when we remove competition and let light down to soil level where their growing points are. This NZ study looked at Timothy persistence. They believe the issues would be the same for perennial ryegrass (prg). file:///C:/Users/User/Downloads/https___www.grassland.org.nz_publications_nzgrassland_publication_2235.pdf
They found the combination of hard grazing in summer and dry weather reduced timothy tiller numbers below what is required for persistence.
"any event such as a drought or severe grazing, combining with moisture deficit, insect, and other stresses to cause a period of tiller death in summer might be seriously detrimental to sward persistence and farmers should be mindful about this when making decisions on summer management options"
I have attached a photo from my farm showing what abundant tillering for persistence with timothy looks like in summer. Notice the tillers are thick and how dark it is down near the soil. This is living, growing, green soil armor which is actively feeding the soil.
Just because optimal recovery is good doesn’t mean more rest time is always better. If the grass in the photo had been allowed to go to seed, it would have slowed down its growth and would pump less liquid carbon into the soil via roots to feed the soil biology. We lifted our soil organic matter from 6% to 9% over five years by keeping pasture green and growing. There was no need to let perennial pasture over recover and go to seed in our humid temperate climate (we got 700 to 1000 mm of rain per year). Green growing plants are the best soil armor if you have the climate to grow them. Brown litter is great soil protection for semi-arid regions because for several months of the year they can’t grow anything green so have to use what they have. Over recovery in our humid climate slows nutrient cycling. When we trample our residual down to feed the soil by mobbing our livestock, we want it to be green too for a more fertile C:N ratio. Too much brown material would make less nitrogen available to your growing pasture and nitrogen is usually the limiting nutrient in growing pasture.
green trampled residual from a deferred pasture which shades sod forming weeds like browntop
This study also looks at the phenomenon we have noticed of stressed grasses bolting to seed quicker. They found when grasses like timothy and prg were eaten low below the collar on the tiller (where the leaf meets the stem) they subsequently sent up a seeding tiller with few to no leaves. This is another reason decking a pasture works against you. Another NZ study by W. Harris looked at how browntop creeps into set stocked pastures.
They feel you can outcompete sod forming weeds like browntop by providing longer recovery times in summer which allows bunch forming grasses like prg to canopy over the browntop and capture light before it gets down to the low growing weed.
“the intense shade developed under a fully formed canopy of ryegrass-white clover far exceeds the shade tolerance of browntop.” Achieving optimal recovery for the plants you want will get you to full canopy. I needed a grazing plan to prevent my cows from getting ahead of the grass in the summer and apparently NZ farmers do to because I know very few farmers who achieve optimal recovery in the summer and their pasture grows slower as a result. A sure-fire way to grow a good crop of browntop and dogstail is to deck your paddocks with livestock in the summer because it removes the competition which could potentially form that competitive canopy. For the same reason if you need to top paddocks do so before the heat and dry of summertime. The researchers also conclude that keeping on top of the springtime vegetative growth in brown top infested paddocks prevents a brown thatch mat from developing. Set stocking usually results in ineffective mosaics where browntop creates a sod bound mass where other plants can't establish. A grazing plan cruise control can help you determine more accurately when you reach a surplus in spring so you can proactively shut up paddocks if required to stay on top of quality while still providing the optimal recovery for the plants you want.
To sum it up if you have a browntop problem it is loving your management! If you want higher quality pasture plants, reduce set stocking after lambing and manage for the optimal residuals and recovery times the bunch forming plants you want need especially in the summer. This will allow them to develop a healthy full canopy to intercept light before it gets down to the near soil surface growing points of sod forming weeds. When grass is growing slow, you need longer recoveries and if it is growing strong shift faster.
Remember don't overcook your recovery times! We are not farming in New Mexico or Zimbabwe. Over recovered pastures grow less tonnage per year and feed your soil less liquid carbon. Repeated over recovery reduces nutrient cycling and leads to more bare soil and thinner tiller density.
Since every month is different, we plan for different recovery times. What makes the holistic planned grazing different is that decisions are made using the round speed for optimal recovery as the benchmark to monitor against. For instance, if a flock of ewes and lambs are on a 16 day round in November and they cannot eat the grass well enough to avoid less than 15% ineffective mosaic, then some paddocks need to be dropped out (shut up for deferred or for hay) or more animals brought into the round. The knee jerk response is to keep the sheep in the paddock another day to tidy up but then the farmer has fallen off the plan and more paddocks will lose quality ahead.
In summer when livestock often get ahead of the grass, the knee jerk response is to speed up the round to feed them, but the farmer will not achieve optimal recovery and the grass on the whole block will grow slower and slower. Being on a grazing plan cruise control gives the farmer the benchmark to know where stock need to stay and for how long to achieve the fastest pasture growth. Then as soon as residuals get lower than their target residual, the farmer knows when they need to get animals away or add paddocks (such as previously deferred grass) or supplement. It is this proactive management that allows farmers to manage dry spells quickly while they still have options and why holistic grazing is sometimes called adaptive planned grazing. This is also why there is no magic number for best recovery time because it depends on the weather and must be adjusted in real time proactively. You can't control the weather but you can grow grass faster than your neighbors with a grazing plan in place as a benchmark for your management. Happy grazing.