Conversion of forestry land back to productive pasture

Abstract

Large areas of pine forests have been logged and the land sold to farmers for converting to pasture in the South Waikato district. This land use change is expected to continue, given the present commodity prices. A trial was conducted on an ex-forest site at Rotorua to assess the feasibility of converting land from forestry to pastoral agriculture. The establishment of pasture (ryegrass and white clover) on an ex-forest site was successful and results after 4 years indicated there were no major problems with the conversion. An application of 4 t lime/ha lifted soil pH levels into the optimum range of 5.8-6.0 and an annual maintenance dressing of 40 kg phosphorus (P) /ha has more than maintained optimum Olsen P levels of 35-45 μg/ml for pasture growth. It is expected however that commercial sites where post-forest soil P levels were lower than on the Rotorua trial site, would require higher capital P fertiliser input. Soil fauna surveys indicated a recolonisation of some soil macro fauna e.g. earthworms, grass grubs and clover root weevil. Recommendations for converting pines to pasture include removal of stumps and forest debris (where practical), vigorous weed control and the application of nutrients such as phosphate that promote pasture production. Keywords: forestry, soil Olsen phosphorus, soil pH, pasture, Pinus radiata

Soil C and N sequestration and fertility development under land recently converted from plantation forest to pastoral farming

“…Intact soil cores, 100 mm diameter and 80 mm in height, were also taken from the middle of each sample depth, at each sampling position, for estimation of bulk density. annual pasture production was assessed from data collected between October 2004 and November 2006 at 4 6 week intervals using the single trim and cut technique from small pasture exclusion cages (3 × 0.22 m 2 per site) (Hawke 2004). annual dry matter (dm) yields are expressed per hectare.…”

Forage responses to lime and nitrogen fertiliser on land converted from pine forest to dryland pasture in Canterbury

“…It is also notable that DM production of the pasture that was established after the triticale was only increased by lime application in the last 4 months (spring and summer) of the reporting period. In a previous lime trial on a former forestry site, Hawke (2004) found that the application of 4 t lime/ha increased pasture production when measured in the second year after conversion. However, the soil in this case was yellow brown pumice and the effect of aluminium toxicity on pasture production was likely to be more pronounced.…”

Pasture composition and production from different cropping sequences in dryland pasture converted from Pinus radiata forest

“…The phenomenon of low reestablishment in balansa clover despite high seed yields in the summer after establishment has been evident at other experimental dryland sites in Canterbury and is the subject of current investigations. Hawke (2004) recorded some colonisation of a 1 ha area by earthworms 3 years after a forest site was converted to pasture in the South Waikato district. However at this 30 ha site, no earthworms were found in the soil 18 months after the first crops and pastures were established.…”

“…The conversion to pasture is subject to a range of constraints that may limit pasture establishment and productivity. These include a low soil pH (4.6. to 4.9) which may lead to toxic levels of available aluminium in the soil; a large soil seed bank of woody weeds such as gorse (Ulex europaeus), broom (Cytisus scoparius) and blackberry (Rubus fructicosus), that may compete with establishing pastures and crops; a large quantity of woody pine debris, leading to a high soil C:N ratio and immobilisation of N during wood decomposition; a poor soil structure due to mulching and cultivation, which may make soils prone to wind erosion in dryland environments; and a lack of earthworms (Hawke 2004;Lloyd et al 2007).…”