Effects of soil fertility on the persistence of dryland cocksfoot and tall fescue pastures

Abstract

<jats:p>The persistence of pastures sown with tall fescue, cocksfoot or mixtures of the two species was evaluated by tiller core measurements on 106 paddocks that had been sown in 1989 or 1991 on dryland east coast sheep/beef farms. In both North and South Island paddocks, cocksfoot was the dominant grass in mixtures of tall fescue and cocksfoot. Tall fescue presence was usually much lower than that of ryegrass and other unsown grasses, regardless of sowing mixture. High levels of cocksfoot were associated with low levels of ryegress, browntop and other perennial grasses. North Island paddocks had higher P levels (Olsen P=25) than South Island paddocks (Olsen P=21) but had lower levels of clover (32%) and higher levels of browntop (26%) than South Island paddocks (52% clover, 13% browntop). In North Island paddocks sown with cocksfoot, there were weak, negative associations of white clover with fertiliser N inputs (r = -0.45) and soil P levels (r = - 0.41). These effects of P and N on clover appeared to be owing to increased cocksfoot dominance at high fertility. In the North Island, the best white clover presence was found in pastures that were low in cocksfoot but high in ryegrass, browntop and other unsown perennial grasses. In the South Island there was no significant association of clover with soil test levels or fertiliser history. Comparison of 1996 measurements made on North Island paddocks with 1991 measurements on the same paddocks indicated that establishment effects could have long-term effects on the persistence of tall fescue and cocksfoot. Inclusion of cocksfoot in the seed mix reduced tall fescue persistence. High levels of perennial ryegrass at establishment were also associated with poor tall fescue persistence. These effects appeared to be more important than soil fertility constraints in reducing tall fescue persistence. The presence of other vigorous grasses, such as ryegrass, during establishment may also reduce or delay cocksfoot dominance and thus improve white clover persistence. Keywords: cocksfoot, dryland, pasture persistence, soil fertility, tall fescue</jats:p>

What factors lead to poor pasture persistence and weed ingress?

“…In 1996, a survey of beef and sheep pastures in the North Island showed that while cocksfoot tolerated low fertility, it responded well to high fertility, was more competitive and suppressed grasses such as browntop and sweet vernal, which grew best at lower fertility. However, at high fertility, cocksfoot also suppressed white clover and tall fescue (Schedonorus phoenix) (Festuca arundinacea) (Smith et al 1998). Similarly, in Waikato hill pastures grazed by cattle, there was an increase in ryegrass and white clover content and decline in weedy grasses, such as browntop, in response to increasing phosphorus application (Ledgard & Brier 1993).…”

“…Ninety-seven percent of the new pastures established well. This resulted in 112% more grazing and farmers reported greater animal production on the new pastures than the resident (mainly) perennial ryegrass-based pastures (Smith et al 1998). Greater drought tolerance and vigour of cocksfoot in a dryland system may also explain why the establishment of vulpia and soft brome (Bromus hordeaceus) was lower in cocksfoot than perennial ryegrass pastures in Canterbury, which is subject to hot, dry summers (Tozer et al 2010d).…”

Can pasture persistence be improved through the use of nonryegrass species?

“…Over time, this leads to a dominance of weeds, and this can be an indicator of poor pasture persistence. Other grass species like cocksfoot have a reputation of being more tolerant of lower soil fertility, and being able to compete better with weeds, resulting in better persistence (Smith et al 1998). Production of cocksfoot however, is still responsive to increasing soil fertility (Smith et al 1998).…”

“…Other grass species like cocksfoot have a reputation of being more tolerant of lower soil fertility, and being able to compete better with weeds, resulting in better persistence (Smith et al 1998). Production of cocksfoot however, is still responsive to increasing soil fertility (Smith et al 1998). Some alternative grasses to ryegrass have a similar or higher requirement for soil fertility (e.g.…”

“…Cocksfoot is a more persistent grass than perennial ryegrass in dryland (Mills & Moot 2010) and lower soil fertility (Smith et al 1998) environments. Earlier survey results (Korte et al 1991) indicated that in ryegrass/cocksfoot mixtures, high rates of cocksfoot (>3 kg/ha) in the seed mix had a negative long-term effect on the ryegrass and white clover presence.…”