The concept of a climax in relation to the fertiliser input of a pastoral ecosystem

Estimation of potassium losses from a grazed dairy farm in Taranaki

“…Adding these two components together gives a mean annual product loss of 0.65 kg K/stock unit (SU) ( Table 2). This is similar to the 0.61 kg K/SU estimated by Middleton & Smith (1978).…”

“…The size of the farmlet, number of Friesian-Jersey crossbred cows grazed and relevant production data is presented in Assume milk contains 0.13OJo K (Hutton et al 1967) Assume 18.25 kg calf at 0.17010 K and 100 kg cow replacement at 0.15% K (Middleton Smith 1978) was measured as the difference between pre-grazing and post-grazing herbage mass for each paddock in the farmlet. Soil samples were collected from each paddock for K analysis by the MAF Quick test (Cornforth 1980) every January.…”

“…During these 4 years the cow produces three calves each at a liveweight of 25 kg or 18.75 kg/year. The body tissue of cows and calves contains 0.15070 and 0.17% K respectively (Middleton & Smith 1978), which equates to an annual loss of 0.18 kg K/cow.…”

“…The principles for modelling the K losses and gains from dairy farms are well known but few attempts have been made to validate the model under field conditions. In New Zealand, only Middleton & Smith (1978) have produced an estimate of the K losses and gains which are likely to occur on a typical Waikato dairy farm.…”

A note on the losses from a phosphate cycle under grazed pasture

“…Middleton & Smith (1978) have drawn up balance sheets for phosphate and other nutrients in a pastoral ecosystem at a climax, and the model is extended here to include important soil components.…”