Pasture responses to phosphorus and nitrogen fertilisers on east coast hill country: 2. Clover and grass production from easy slopes

Abstract

From 2000 to 2002 a trial series was established on seven farms from Wairoa (northern Hawke's Bay) to Moeraki (North Otago), with contrasting amounts of spring-summer rainfall, to evaluate the pattern of pasture responses to a range of rates of nitrogen (N) fertiliser and a range of soil phosphorus (P) levels. Small plots excluded from grazing were established on flat to gently sloping land containing pastures that had been established for many years. This paper describes the clover and grass component production responses to N fertiliser and to a range in soil P status at each site. In early spring, in all years, the grass components of pasture at all sites except Marlborough, showed a significant response in dry matter (DM) production to N fertiliser applied in mid winter. These responses A07058; Online publication date 6 June 2008 Received 27 July 2007 accepted 13 March 2008 continued into late spring-autumn at most sites/ years. The consistency from year to year of the relative grass response in spring to N fertiliser allowed significant regression relationships to be developed for the 3-year dataset for the North Island sites. The same result did not occur in Marlborough, presumably because low rainfall limited pasture growth, or at Moeraki (not measured). The effects ofN fertiliser on clover production throughout the total season tended to be the opposite of those for grass production. There was generally no response to N fertiliser in early spring but a marked and consistent decline in clover production in late spring-autumn with increasing rate of N fertiliser application. Compared with clover production from plots that received 90 kg N ha -1 , the average clover production in late spring-autumn from plots that received zero N application, was up to the order of three times greater at the Wairoa, Puketapu and Wallingford sites, and about 50% greater at the Waipawa and Wairarapa sites. There was a consistent response by clover in both early spring and in the late spring-autumn seasons, to an increase in soil Olsen P test. On the four northern-most sites an increase in Olsen P test from less than 10 to about 20 raised clover production by about 100% in early spring and by a greater proportion in late spring-autumn. This was in direct contrast to the absence of a response by the grass component during the same period. The management implications of the contrasting effects of N and P fertilisers on pasture clover and grass composition are discussed.

Pasture responses to phosphorus and nitrogen fertilisers on east coast hill country: 3. Production from steep slopes

“…The response by pasture on steep slopes to increase in soil P was mainly limited to early spring, whereas on easy slopes most sites also responded in late spring-autumn (Gillingham et al 2008). The clover component of the pasture was responsive to increase in soil P test in both seasons on both land classes.…”

“…This was used to derive an estimate of clover production and, by difference, grass production. The limitations of this approach were discussed by Gillingham et al (2008). The pasture was then trimmed to approximately 900 kg Dm ha -1 residual pasture and clippings removed.…”

Influence of phosphorus inputs and sheep treading on soil macrofauna and mesofauna in hill pastures

“…At grass grub densities similar to those found in the Allophanic high-intensity pasture, productivity of ryegrass clover mixtures can be reduced by up to 50% (East et al 1982). Indeed, their feeding behaviour was apparent with a decline in root mass and legume contribution to the pasture (Table 2), as Gillingham et al (2008) observed an increase in legumes with increased phosphate application. Competition with other herbivorous fauna (i.e.…”

Pasture production from a long-term fertiliser trial under irrigation

“…This Olsen P concentration is just below the average of 20 mg/ml derived for sedimentary soils (Morton & Roberts 2010) and less than the critical level for sedimentary soils of 26Á32 mg/ml reported by Edmeades et al (2006), but falls within the scatter of field trial results presented in their paper. Furthermore, work by Sinclair et al (1997) and Gillingham et al (2007Gillingham et al ( , 2008 showed that there is little advantage in sheep pastures of Olsen P concentrations greater than 20 mg/ml. Nguyen et al (1989) showed that SSP application resulted in high-producing ryegrass and clover pastures in the initial years, and that cessation of fertiliser on some plots in 1958 resulted in an increase in weeds and poor producing/lower fertility grasses and a decrease in clover content.…”

“…There were several occasions over the duration of the trial when this irrigation scheduling system was not applied, for a variety of reasons. These occurred in 1954 and 1984 (Rickard & McBride 1987) and latterly in 2007and 2008. Between 1952and 1958, the trial evaluated the effects of five different SSP treatments (Rickard & Moss 2012) initially applied in autumn, but in later years applied in late winter (Rickard and McBride 1987;Nguyen et al 1989).…”