Pasture degradation

This farm in previous years has been very heavily stocked. There s been a certain amount of pasture degradation. That s something we have seriously looked at in the last five years, just trying to re-estabhsh pastures. .. a lot of the other farms. .. particularly if they are ex-dairy they re very flat with not a tree in sight because they rotationally grow Lucerne and the farmers knocked down aU the trees because they didn t want to drive around trees. (TB2)... 

Dietary additives can affect the microbiota that are associated with the faeces of animals and degradation of the faeces may be impaired because of the influence of the excretory products on insects, microbes and fungi. The microbiota in the soil and waste material may be affected, thus altering the fertility of the pasture and sustainability of other wildlife. These microbiota can be used as dietary ingredients for animals, so inhibition of their production would be an unsatisfactory consequence of dietary additives. ... 

Bridge, B.J., Mott, J.J., Winter, W.H. Hartigan, R.J. (1983). Improvement in soil structure resulting from sown pastures on degraded areas in the dry savanna woodlands of northern Australia. Australian Journal of Soil Research, 21, 83-90. Cionco, R.M. (1972). A wind profile index for canopy flow. Boundary Layer Meteorology, 3, 255-63. 

Soils/Land surface About 10%—20% of agricultural lands have degraded in many respects (loss of fertility), which has brought a decrease (during the last 50 years) in yield by 18% on cultivated lands and by 4% on pastures. 

C Inputs Forest (tons C ha-l) Degraded Pasture (tons C ha l) Productive Pasture (tons C ha4)... 

Table 6.4 Dry matter production of a 12-year-old degraded Panicum maximum pasture after weeding and fertilizer application at Paragominas on a yellow latosol (Haplustox).

Table 6.6 P and nitrogen concentration (% of dry weight) of forage grass (Jiyparrhenia rufa), herbaceous weedy vegetation and litter of a 10-year-old degraded pasture in eastern Bra2ilian Amazonia.

If not grazed, or if the pasture is not burned, most of the P absorbed in plant tops will be immobilized by plant tissue and, thus, will be unavailable in the soil. Transfer of P and N by nutrient resorption in forage plants and in the weedy vegetation prior to leaf fall induces low nutrient concentration in litter (Table 6.6) and may in part explain the decreasing amount of available soil P often associated with an increase in the weed biomass of a degrading pasture or with pasture age. Without this biological immobilization, however, these nutrients would be more vulnerable to loss through runoff and erosion. 

The secondary forest at Paragominas has recovered much of the net N mineralization capacity that is characteristic of primary forest, and the improved (reformed) pasture has higher net nitrification than the degrad-... 

Table 6.7 Mineralization indices and N trace gas emissions for soils from primary forest, secondary forest, reformed pasture, and degraded pasture at Fazenda Vitoria. ...

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