The profitability and risk of dairy cow wintering strategies in the Southland region of New Zealand

A survey amongst stakeholders in 2007 identified wintering systems with less environmental impact and a reliable supply of high quality feed, which are cost effective and simple to implement, as one of the top three issues requiring research and demonstration in the Southland region of New Zealand. This study used a modelling approach to examine the cost effectiveness, exposure to climate-induced risk and major economic drivers of four selected wintering strategies, i.e. (1) grazing a forage brassica crop on support land (Brassica system), (2) grazing pasture on support land (All pasture system), (3) cows fed grass silage, made on the support land, on a loafing pad where effluent is captured (Standoff system), and (4) cows fed grass silage, made on the support land, in a housed facility where effluent is captured (Housed system). The model was driven by virtual climate data generated by the National Institute of Water and Atmospheric Research and economic input data from the DairyNZ Economics Group for the 08/09 season with a milk price of NZ$4.551/kg milksolids (fat + protein). The Housed system had the highest average (± STDEV) operating profit (profit after depreciation but before interest charges) over 35 independently simulated climate years (NZ$743 ± 122/ha), followed by All pasture (NZ$681 ± 197/ha), Standoff (NZ$613 ± 135/ha) and Brassica (NZ$599 ± 212/ha). This ranking was sensitive to the assumptions and treatment of capital costs. The Housed system was the least exposed to climate-induced risk with a coefficient of variation of operating profit of 16% compared to 35% of the Brassica system. The four systems demonstrated different financial strengths and weaknesses that largely balanced out in the end. The Brassica system is a high risk system from an environmental perspective and the All pasture system an unlikely alternative because of scarcity of suitable land. Both the Housed and Standoff systems appear to be cost effective alternatives that allow high control over cow feeding, body condition and comfort over winter. Furthermore, both systems have the potential to provide high control over the storage and release of animal effluent onto land, thus saving fertiliser costs and reducing environmental footprint.Simulation modelling Housed wintering Loafing area Brassica Profitability Pasture-based

The Kaapvaal Craton, South Africa: no evidence for a supercontinental affinity prior to 2.0 Ga?

We briefly examine the possible antiquity of the supercontinental cycle while noting the likely unreliability of palaeomagnetic data >ca.1.8 Ga, assuming a gradual change from a magmatically dominated Hadean Earth to a plate tectonically dominated Neoarchaean system. A brief review of one of Earth’s oldest cratons, Kaapvaal, where accent is placed on the lithostratigraphic and geodynamic-chronological history of its cover rocks from ca. 3.1 to 2.05 Ga, forms the factual basis for this article. The ca. 3.1–2.8 Ga Witwatersrand–Pongola (Supergroups) complex retroarc flexural foreland basin developed while growth and stabilization of the craton were still underway. Accretion of relatively small composite granite-gneiss-greenstone terranes (island arc complexes) from both north and west does not support the formation of a Neoarchaean supercontinent, but may well have been related to a mantle plume which enhanced primary gold sources in the accreted terranes and possibly controlled the timing and rate of craton growth through plate convergent processes. Subsequent deformation of the Witwatersrand Basin fill with concomitant loss of ≤1.5 km of stratigraphy must have been due to far-field tectonic effects, but no known mobile belt or even greenstone belts can be related to this contractional event. At ca. 2714–2709 Ma, a large mantle plume impinged beneath the thinned crust underlying theWitwatersrand Basin forming thick, locally komatiitic flood basalts at the base of the Ventersdorp Supergroup, with subsequent thermal doming leading to graben basins within which medial bimodal volcanics and immature sediments accumulated. Finally (possibly at ca. 2.66–2.68 Ga), thermal subsidence enabled the deposition of uppermost Ventersdorp sheet-like lavas and sediments, with minor komatiites still present. Ongoing plume-related influences are thus inferred, and an analogous cause is ascribed to a ca. 2.66–2.68 Ga dike swarm to the north of the Ventersdorp, where associated rifting allowed formation of discrete ‘protobasinal’ depositories of the Transvaal (ca. 2.6–2.05 Ga Supergroup, preserved in three basins). Thin fluvial sheet sandstones (Black Reef Formation, undated) above these lowermost rift fills show an association with localized compressive deformation along the palaeo-Rand anticline, north of Johannesburg, but again with no evidence of any major terrane amalgamations with the Kaapvaal. From ca. 2642 to 2432 Ma, the craton was drowned with a long-lived epeiric marine carbonate-banded iron formation platform covering much of it and preserved in all three Transvaal Basins (TB). During this general period, at ca. 2691–2610 Ma, the Kaapvaal Craton collided with a small exotic terrane [the Central Zone (CZ), Limpopo Belt] in the north. Although farfield tectonic effects are likely implicit in TB geodynamics, again there is no case to be made for supercontinent formation. Following an 80–200 million years (?) hiatus, with localized deformation and removal of large thicknesses of chemically precipitated sediments along the palaeo-Rand anticline, the uppermost Pretoria Group of the Transvaal Supergroup was deposited. This reflects two episodes of rifting associated with volcanism, and subsequent thermal subsidence within a sag basin setting; an association of the second such event with flood basalts supports a plume affinity. At ca. 2050 Ma the Bushveld Complex intruded the northern Kaapvaal Craton and reflects a major plume, following which Kaapvaal–CZ collided with the Zimbabwe Craton, when for the first time, strong evidence exists for a small supercontinent assembly, at ca. 2.0 Ga. We postulate that the long-lived evidence in favour of active mantle (cf. plume) influences with subordinate and localized tectonic shortening, implicit within the review of ca. 3.1–2.05 Ga geological history of the Kaapvaal Craton, might reflect the influence of earlier Precambrian mantle-dominated thermal systems, at least for this craton.University of Pretoria and the National Research Foundation of South Africa.http://www.tandfonline.com/loi/tigr20nf201