Growth Rates Monitored

Growth Rates Monitored.

Peter Burton
7th December 2009


The three properties that Eco-Logic Soil Improvement monitors have produced fascinating results for the month of November.

Galatea (irrigated) 88kgDM/ha/day (79% increase over November ’08)
Reporoa 79kgDM/ha/day (20% increase over November ’08)
Edgecumbe 76kgDM/ha/day (22% increase over November ’08)

Grass growth is monitored with cages. Each month at intervals of approx. 30 days the grass in the cages is cut, weighed and dried, and the growth for the period calculated.

The process is as has been done since the 1960’s and although the accuracy and relevance to actual total farm growth can always be debated, the results do allow comparison with historic figures.

The use of multiple cages reduces the likelihood of rogue results, and with all data particularly where many factors have an effect on the outcome, the results are referenced against all other relevant information available.

The questions asked are, “Do these results make sense when related to pasture covers at the time of the last cuts and the known maintenance requirements for each property, and do they make sense when related to historic data and the results from the other monitor properties?”

Common to each monitor property at present is the strong clover growth and the minimal use of fertiliser nitrogen. The Edgecumbe property has received no fertiliser nitrogen since last autumn, and the two others received 15kgN/ha in late winter.

One of the reasons for the strong growth during November is the 30 days between cuttings. Rotational grazing, i.e. spelling of pasture between grazing, evolved because total growth is substantially, up to double, that of set stocked pastures.

A 30 day rotation means 30 days between grazing, or 3.3% of the farm grazed each day. There is no magic grazing interval figure, and the optimum changes with the rate of growth, but experience suggests that 30 days between grazings is likely to maximise growth over the summer period.

What we do know from experience this spring is that where grazings have been more frequent less total feed has been grown compared to growth on properties where a genuine 27 –30 day grazing interval has been maintained.

For maximum production grass needs to enter the rapid growing phase, often in spring around 3 weeks (21 days) after grazing. At this time growth can be very rapid, 100+kgDM/ha/day, energy in the plant rapidly increases with energy transferred to the root system providing the grunt for rapid regrowth after the next grazing.

To check the validity of this graze a small area to a low cover three times at one week intervals and observe the result, but only a small area!

The usual reason given for relatively short intervals between grazings is the need to control pasture quality.

On the properties monitored and the results from other properties regularly using DoloZest and CalciZest as part of their total nutrient input, quality remains high and optimum production is achieved even when pastures are quite long, up to an average of 6 inches in length with some stalk and seedhead.