Management practices involving legume leys, grain legumes, and no-tillage and stubble retention, along with nitrogen (N) fertiliser application for wheat cropping, were examined for their effectiveness in increasing soil organic matter (0-10 cm depth) from 1986 to 1993 in a field experiment on a Vertisol at Warra, Queensland. The treatments were (i) grass + legume leys (purple pigeon grass, Setaria incrassata; Rhodes grass, Chloris gayana; lucerne, Medicago sativa; annual medics, M. scutellata and M. truncatula) of 4 years duration followed by continuous wheat; (ii) 2-year rotation of annual medics and wheat (Triticum aestivum cv. Hartog); (iii) 2-year rotation of lucerne and wheat; (iv) 2-year rotation of chickpea (Cicer arietinum cv. Barwon) and wheat; (v) no-tillage (NT) wheat; and (vi) conventional tillage (CT) wheat. Fertiliser N as urea was applied to both NT wheat and CT wheat at 0,25, and 75 kg N/ha. year. The CT wheat also received N at 12.5 and 25kg N/ha. year. After 4 years, soil organic carbon (C) concentration under grass + legume leys increased by 20% (650 kg C/ha. year) relative to that under continuous CT wheat. Soil total N increased by 11, 18, and 22% after 2, 3, and 4 years, respectively, under grass + legume leys relative to continuous CT wheat. These increases in soil organic matter were mostly confined to the 0-2.5 cm layer. After the start of wheat cropping, organic C and total N levels declined steadily but were still higher than under CT wheat and higher than initial values in December 1985. Although 2-year rotations of lucerne-wheat and medic-wheat had a small effect on soil organic C, soil total N concentrations were higher than in the chickpea-wheat rotation and continuous CT wheat from November 1990 to November 1992. Soil under chickpea-wheat rotation had organic C and total N concentrations similar to continuous CT wheat, although from the former, about 70 kg/ha. year of extra N was removed in the grain from 1989 to 1993. No-tillage practice had a small effect on soil organic C, although total N concentration was higher than under CT wheat in November 1993. These effects were mainly confined to the surface 0-2.5 cm depth. The C to N ratio was only affected in soil under grass + legume leys, and no-tillage treatments. These data show that restoration of soil organic matter in Vertisol requires grass + legume leys, primarily due to increased root biomass, although soil total N can be enhanced by including legume leys for longer duration in cropping systems in the semi-arid and subtropical environment.

No abstract

No abstract

In 12 pregnant sows (Sus scrofa domestica), containing 144 live fetuses, placental blood flow was measured by the indicator fractionation technique using radioactive microspheres. In 8 of these litters, which contained 96 live fetuses, placental blood flow was obtained in absolute units. Significant positive correlations were observed between placental blood flow and placental weight, between placental blood flow and fetal weight, and between placental weight and fetal weight. It is clear that the runt, by comparison with his littermates, has a low birthweight in association with a small placenta and a low placental blood flow.