Mortality data on 5163 Romney X Suffolk lambs were collected at Winchmore Irrigation Research Station from 1976 to 1.981. M?rtality from birth to tailing (25 days) for single, twm, and triplet births was 14.1, 14.7, and 33.0% with mean birthweights of 5.2, 4.1, and 3.3 kg respectively. Ninety-four percent of all deaths occurred within 72 h ofbirth. Dystocia accounted for 50.4% of all single deaths and starvation/exposure for 45.0% ofall multiple deaths. The proportion ofewes assisted at lambing increased with birthweight above 4.5 kg to reach almost 19 and 8% for single and twin births respectively. If lambs that were assisted at birth, but survived to weaning, are regarded as potential deaths, the overall potential mortality of single and twin lambs was 27.9 and 20.2% respectively. Ewe liveweight gain during the last 6 weeks of pregnancy was associated with increased birthweights of single and twin lambs (P< 0.05). A liveweight change of approxi.mately 10 kg in ewes was required to alter birthweight by 0.5 kg in both single and twin lambs. Single l~mb mortality was not significantly affected by liveweight gain or ewe livewei~ht at lamb~ng on.either a between-mob or a within-mob basis. ThIS suggests that with single bearing ewes it may be more economical to save feed for lactation when feed requirements of ewes are high, rather tha~to offer it in late pregnancy. However, when multiple bearing ewes were offered additional feed in la~e pregnancy to increase liveweight, lamb mortality was reduced, suggesting merit in improved pre-lamb feeding for these ewes.

Sheep faeces containing strongylate eggs were applied to plots of perennial ryegrass, prairie grass, or chicory mixed with white clover, or lucerne without white clover. Plots were later harvested within four height zones and the herbage mass, numbers, and species of gastro-intestinal nematodes determined. Ryegrass, prairie grass, and lucerne plots produced similar yields of herbage dry matter (DM) (3580, 3180, and 3230 kg DM/ha respectively), whereas chicory produced 2250 kg DM/ha. Ryegrass-, prairie grass-, and chicory-based swards had similar proportions of herbage DM within each height zone, the quantities declining with increasing height. Lucerne swards had less DM in the central height zones than other swards but proportionally more above 125 mm from ground-level. Larvae from 0.73% of eggs were recovered, but the rate was influenced by herbage species. The grass-based swards had higher larval populations than had lucerne or chicory, and lucerne had more than chicory. Larval density tended to be higher in the 26-75 and 76-125 mm zones than in the 0--25 and greater than 125 mm zones, which were similar. Chicory swards offered the best opportunity to reduce larval intake in grazing animals as they had the lowest populations per unit of herbage mass. This was, however, associated with a lower herbage mass. A92043Lucerne offered low larval popUlations together with high nutritive value and herbage mass making it a highly suitable forage for growing lambs.

To determine the best method of pasture establishment on non-cultivable hill country (>20o slope), four treatments were compared in one year on north and south aspects at four sites with contrasting climates and soil types. Sites were located in Waikato (1), Hawke's Bay (2) and Canterbury (1). The treatments included seed mix (grasses, legumes and herbs (GLH); legumes only (LEG)) and sowing time (spring; autumn). Six weeks after sowing, seedling establishment, as a percentage of viable seeds sown, was: i) greater on south than north aspects for perennial ryegrass (31% vs 18%) and birdsfoot trefoil (5% vs 4%); ii) greater for total sown species (14% vs 8%), subterranean clover (7% vs 4%) and red clover (25% vs 14%) in the GLH than LEG mix, but greater for white clover in the LEG than GLH mix (17% vs 8%); iii) greater in autumn than spring for perennial ryegrass (36% vs 13%) and total sown grasses (22% vs 9%) but greater in spring than autumn for lotus (6% vs 3%). Plantain established well in spring in summer-wet environments, while in summer-dry environments establishment was greater in autumn. Broadcasting seed on south aspects during autumn is likely to result in the highest establishment of sown grasses and legumes, but not necessarily of herbs. The trials were conducted in an unusually wet season. Repeating a subset of the treatments at these sites will provide a greater understanding of responses to climatic variation. Keywords: pasture renewal; pasture establishment; pasture mixtures; oversowing.

No abstract

We determined decadal changes in soil carbon (C) and nitrogen (N) due to different irrigation regimes and phosphorus fertilization of pastures. Archived soil samples (0–75 mm) collected annually from two long‐term trials in New Zealand were analyzed for %C and %N from three P input treatments (ranging from 0 to 376 kg superphosphate ha−1 yr−1, 1952–2009) and three irrigation treatments (unirrigated and irrigated when soil moisture content fell below either 10 or 20%, 1959–2002). In the fertilizer trial, soil C increased linearly from 2.7 to 4.2%, and there was no difference in rates of increase in C between treatments, despite much greater aboveground production when P was added. This lack of difference was attributed to higher stocking rates on treatments with higher production, and to the possibility that root inputs (which differed less between treatments) was a more important control of soil C accumulation. Nitrogen (%) was lower in the unfertilized than fertilized treatments due to lower clover N fixation, which was constrained by P availability. Soil C (%) was significantly greater in the unirrigated treatment than the irrigated treatments throughout the trial. Aboveground production was much greater in the irrigated than dryland treatment but root biomass was lower. Irrigation must have increased C and N losses, possibly via increased respiration rates during seasonally dry periods. Our study showed that P fertilizer application did not result in an increase in surface soil C and that flood irrigation resulted in a constrained increase in surface soil C content.