Human nature being what it is, a degree of nervousness about the amount of growth over the coming summer is to be expected, however past growth records combined with the digging of a few holes will help with feed budgeting.
Here in the Rotorua district the December growth figures since 1989 we have give a mean of 60kgDM/ha/day, with a range of 40 – 88kgDM/ha/day.
Figures from Edgecumbe district over the last 7 years show growth ranging from 47 – 86kgDM/ha/day with a mean of 66kgDM/ha/day. There are long term pasture growth figures for all districts.
Based on this information growth in December is quite reliable and the examination of physical soil structures and rooting depth will further help predictions.
Soil is a living breathing organism and therefore able to respond, often quite rapidly, to changing climatic conditions. After a prolonged dry period a crust may form on the soil surface, possibly in an attempt to limit moisture loss as it soon disappears after a small amount of rain.
Pasture plants have the ability to send roots to a depth of 0.8m enabling them to access moisture and nutrient from areas usually little affected by our typical short term dry spells over summer.
Recent digging on clients’ properties has shown strong root depth to spade depth (25cm). The bulk of the root is white indicating that it has formed during winter and early spring prior to the rapid growth phase which starts with soil temperatures reaching a daily minimum of 10°C.
There has been little evidence of roots matted in the top 7.5 – 10.0cm of the soil. Matting of root usually only occurs if there is hard layer at about 10.0cm. In some instances if water soluble fertiliser has been regularly applied plant roots may congregate close to the soil surface and this is often accompanied with a hard layer just below.
The ability of soil to withstand the pressure exerted by animal feet is due to the activity of beneficial soil dwellers, predominantly earthworms, bacteria, and fungi. For these essential workers to provide the assistance necessary there must be sufficient available calcium.
Where excess fertilizer nitrogen is applied soil calcium levels may reduce rapidly with soil pH levels declining to levels of less than 6.0. Soils may become compacted and unable to provide the moisture and nutrient necessary for strong clover growth over summer.
It is clover that provides strong growth over summer as most pasture grasses only remain in a vegetative stage at soil temperatures less than 20°C. Above that they become stressed and a seed head supported by a stalk rapidly forms, nearly always occurring in the first week in November.
Calcium is the nutrient most influential in clover growth as clovers are often 3 – 4 times higher in calcium than grasses.
Common to nearly all the properties visited recently is the annual application of dolomite at the rate required to provide magnesium lost to production. Dolomite also contains calcium, has a stronger pH modifying effect than lime, and is an outstanding conditioner of physical structures.