Early performance of oversown pasture mixtures on non-cultivable hill country at four geo-climatically different sites

Abstract

Abstract A trial was conducted on non-cultivable hill country (>20o slope) at four sites to determine the effect of seed mixture (grass+legume+herb vs legume) and sowing time (spring vs autumn) on plant establishment. Sites were in Canterbury (1 site), Hawke's Bay (2) and Waikato (1) on north and south aspects and differed predominantly in climate. In the first spring after sowing (12 months after spring sowing; 6 months after autumn sowing), sown legume and total sown species contributions (% of total dry matter (DM)) were: greater in the grass+legume+herb than legume mixtures; greater when sown in spring than autumn (15 vs 7% for sown legumes and 41 vs 21% for total sown species); and similar on north and south aspects. Sown grass contribution was greater from autumn than spring sowing (79 vs 65%) while sown herb contribution was greater from spring than autumn sowing (15 vs 1%), but both were similar across aspects. The contribution of unsown species was high, averaging 59% in springsown swards and 78% in autumn-sown swards. There was no effect of seed mixture or sowing time on DM production in spring (September-November; averaging 2660 kg DM/ha in Canterbury and 5080 kg DM/ha at a Hawke's Bay summer-moist site). However, DM production was greater in spring- than autumn-sown swards in summer at both sites (December-February; Canterbury: 1980 vs 1520 kg DM/ha; Hawke's Bay: 3980 vs 2670 kg DM/ha). In a wet year, broadcasting seed during spring rather than autumn is likely to result in the highest early DM production and contribution of sown species (sown grasses, legumes and herbs) in the sward. The high unsown species contribution emphasises the importance of dealing with the seed bank before establishment, especially when sowing in autumn. Keywords: seed mixture; pasture establishment; botanical composition; unsown species ingress; pasture improvement.