Effect of rate and time of nitrogen application from autumn to midwinter on perennial ryegrass-white clover dairy pastures in western Victoria. 1. Growth and composition

Citation
Fr. Mckenzie et al., Effect of rate and time of nitrogen application from autumn to midwinter on perennial ryegrass-white clover dairy pastures in western Victoria. 1. Growth and composition, AUST J AGR, 50(6), 1999, pp. 1059-1065
Citations number
27
Categorie Soggetti
Agriculture/Agronomy
Journal title
AUSTRALIAN JOURNAL OF AGRICULTURAL RESEARCH
ISSN journal
00049409 → ACNP
Volume
50
Issue
6
Year of publication
1999
Pages
1059 - 1065
Database
ISI
SICI code
0004-9409(1999)50:6<1059:EORATO>2.0.ZU;2-2
Abstract
Field experiments were carried out at 2 sites to study the effects of time and rate of nitrogen (N) application from autumn to midwinter on perennial ryegrass-white clover pasture dry matter (DM) yield and species composition . Nitrogen (0, 15, 25, 30, 45, and 60 kg/ha) was applied in mid-April, earl y May, mid-May, early June, and mid-June 1996 onto a grazed pasture. Dry ma tter yield was estimated when perennial ryegrass in the 45 kg N/ha treatmen t reached the 3-leaf stage of development. Species composition estimates we re made on all plots in autumn, late winter, and late spring (November). A second DM yield estimate was taken one regrowth cycle after the primary DM yield estimate to determine residual N impact on pasture growth, and then t he pastures were returned to the grazing routine of the farm. Increasing levels of N fertiliser resulted in a linear (Site 1) and curvili near (Site 2) primary DM yield response. Residual DM yield responses were l inear at both sites. The highest primary DM yield response at Site 1 was 9. 1 kg DM/kg N (mid-April application), whereas the highest residual N respon se was 9.4 kg DM/kg N (mid-May application). The time taken for the 45 kg N /ha treatment to reach the 3-leaf stage of development ranged from 38 (earl y June application) to 47 (mid-April application) days for the primary harv est, and from 46 (early May application) to 72 (early June application) day s for the residual harvest. At Site 2, the highest primary DM yield respons e to N was 15.8 kg DM/kg N at 45 kg N/ha (mid-April application), whereas t he highest residual N response was 8.3 kg DM/kg N (mid-June application). T he time taken for the 45 kg N/ha treatment to reach the 3-leaf stage of dev elopment ranged from 24 (early June application) to 36 (mid-April and early May applications) days for the primary harvest, and from 30 (mid-April) to 57 (early June application) days for the residual harvest. Based on the cu rrent cost of urea, the study concluded that N fertiliser use during autumn to midwinter is economically viable for dairy farmers. Botanical composition was unaffected by N application. There were no treatm ent effects on botanical composition of the sward at either site the follow ing spring (November). It is concluded that a 'once-off' strategic N applic ation up to 60 kg N/ha during autumn to midwinter is not likely to influenc e dairy pasture composition in western Victoria.