No abstract

There has been a marked increase in the use of cereals for supplementary grazing and silage for the developing dairy industry in the South Island. Cereals provide high energy supplement in autumn/winter or can be used as a high fibre source in spring. Variation in yield potential in cultivar trials in Canterbury was assessed for autumn and spring-sown crops. The aim was to produce high quality cereal feeds with good yield potential by examining the variation among species and cultivar selections in well managed trials. Single-bite crops sown in early autumn in Canterbury provide up to 5.5 t/ha herbage DM yield with at least 17.5 % protein, 12% total soluble carbohydrate including starch (TSC) and metabolisable energy (ME) of 11.3 MJ/kg in mid-June. Multiple graze types (eg. Doubletake triticale) with similar winter productivity and quality to single-bite crops produced an additional 13.5 t/ha biomass for a silage crop. At ensiling, this cultivar had 9.3 MJ/kg ME with mean 19.5% total soluble carbohydrates. Spring-sown cereals for silage produced up to 20 t/ha. Harvest timing was a significant factor in the wide range in quality of herbage for ensiling. Cultivar means ranged from 7.0 - 12.8% DM for protein, 8.7- 31.6% DM for TSC and 8.3-10.5 MJ/kg DM for ME. More mature herbage had reduced organic matter digestibility and higher TSC but reduced ensilability at DM content in excess of 40%. Keywords: dairying, fibre, forage, herbage quality, metabolisable energy, near infrared reflectance spectroscopy, supplements

Fifty-eight spring malting barley crops (Hordeum vulgare L. 'Triumph') were monitored in the Rangitikei district, New Zealand (40°20'S), over three seasons beginning 1987/88 and covering a wide variation in soil moisture conditions during grain filling but small deficits before anthesis. The objectives were to: (1) document the range of variability of grain yield among locations and years; (2) determine if systematic patterns occurred in the dry matter (DM) accumulation and nitrogen (N) uptake; and (3) evaluate the effects these processes have on the partitioning of DM and N between the grain and the rest of the plant. Mean yearly grain yields (14% moisture) were 6.85, 5.12, and 5.07 t/ha, respectively. Grain number/m 2 accounted for 79% of the variation in grain yield. On average, 63% of the N in the above ground crop was derived from soil reserves, and 87% of the total N uptake occurred before anthesis. Pre-anthesis processes had a major effect on crop characteristics at maturity. For example, the level of crop N at anthesis (indicative of pre-anthesis N uptake) was a good predictor of the extent of post-anthesis partitioning H93059Received 30 August 1993; accepted 30 November 1993 of N to the grain (r = -0.75). Conversely, high postanthesis N uptake was generally not related to grain N concentration. Therefore, under dryland conditions, there is scope for improving yield by late applications of N without causing grain quality reductions. Management options for obtaining high yields of malting barley under non-irrigated conditions are discussed. These include the use of crop N concentration at anthesis as an indicator of crop N status.

Variation in yield and quality of malting barley (Hordeum vulgare L. 'Triumph') are major problems for both producers and processors in the Manawatu, New Zealand. Climatic variation is partially responsible for this. However, crop management options may enable the variation to be reduced. The effects of sowing date and nitrogen (N) fertiliser on yield and quality of malting barley were evaluated over two seasons. In 1987/88, a grain yield of 7.0 t/ha was achieved with optimal management. Yields in 1988/89 were approximately half those in the previous season because of drier conditions during grain filling and a greater incidence of disease. N uptake was lower in the second season, but this did not result in lower grain N content and, therefore, improved quality because dry matter (DM) yield was also lower. Grain N concentrations were significantly higher in the late sowings in both seasons. Differences in grain N concentrations were related to the timing of N accumulation in the plant. Over all sowings, the contribution of post-anthesis N uptake relative to total grain N was negatively related to grain N concentration (r =-0.78). This indicated that late N uptake may not always be detrimental to quality as the processes of carbon and N accumulation are closely linked during grain filling. The maintenance of green leaf area by fungal disease control or timely irrigation is considered important for maintaining high grain quality as these prolong the accumulation of DM during grain filling.