Ten years of grassland research at Kirwee

Press, 5 March 1982, Page 18

Ten years of grassland research at Kirwee

By

DR EUAN VARTHA and HOWARD BEZAR,

D.5.1.R., Lincoln.

Ten years ago this month, the Grasslands Division of the D.S.I.R. took up a lease of 30 hectares of the Woodlands Park property of Hugh and Helen Williams at Kirwee.

ent but as clover growth was poor during the drought, subsequent pasture growth was limited by low levels of nitrogen. Nitrogen being a major limitation of growth, Nui did , not get a chance to express its superiority in - dryland conditions. One major . advantage of the Nui systems was its ability to recover growth rapidly with the first rains in autum. This improved the ■ nutrition of ewes prior to tupping and resulted in . higher lambing percentages. However, the growth advantage did not continue long enough to reflect in higher yeidls of meat per hectare. . This dryland situation contrasts strongly with the extremely high production which can be obtained from Nui under irrigation. In another trial at Lincoln, on a light Templeton soil an irrigated Nui farmlet (with 30 per cent of the area in Matua prairie grass) produced an astounding 563 kg. meat per hectare which illustrates the very high yeilds attainable on irrigated soils. Such high potential reflects the advantages of irri-

gation promoting pasture growth,’, intensive utilisation and high performance stock.

The . challenge facing grasslands researchers at the time was ts find out what levels of production could be achieved with the then new grasslands cultivars Nui and Tama. Kirwee was chosen as a typical Canterbury dryland site with light droughty soils. With considerable interest in the Central Plains irrigation scheme, Kirwee was also a suitable site • for comparing production levels on irrigated and dryland farms. . Too frequently proposals for irrigation were based on the economics of dry matter comparisons from pasture rather than on the economics of whole farming systems. The Kirwee site, therefore, offered researchers an opportunity to provide farmers with some realistic information on grassland systems for Canterbury. Nui and Ruanui ryegrasses were compared on‘a dryland pasture over seven years. This showed that under severe test conditions Nui gave at least as good a performance as Ruanui. Both grasses were persist-

The use of Matua is complementary with perennial ryegrass as it produces a lot of feed in both autumn and early spring, which coincides with tupping and lambing. Thus with improved feed supplies during these crucial periods there is an opportunity to spell Nui before and after the winter break-graz-ing.

Tama was sown on 50 per cent of the farmlet. One paddock was a pure sowing of Tama and two paddocks were overdrilled into lucerne. The dryland lucerne farmlet produced approximately 30 per cent more meat/ hectare when Tama was satisfactorily established in autumn. The lucerne was persistent and with rotational grazing in autumn blue-green aphids were not a problem. Tama crops were established on cultivated ground satisfactorily, however, only in reasonably wet years, was it possible to establish Tama successfully from overdrilling. When Tama was successfully established, hay was made from the lucerne far in excess of requirements. When poor Tama establishment meant there was a feed deficit in spring, little hay could be made. Irrigation ensured the successful establishment of overdrilled Tama which yielded 400 per cent more herbage than the dryland Tama. However, under the wetter conditions the lucerne (Wairau and Saranac) did not persist satisfactorily beyond four years. High herbage yields of lucerne supported a very high

This system, combines the best features' of two grass species and illustrates the considerable. potential which, exists for intensification of sheep production by irrigation on light land. . Returning to the Kirwee work, the Grasslands Division was particuarly keen to measure the effectiveness of systems which were predominantly all-lucerne with some supplement from grasses for cool-season production. Tama being an annual ryegrass with growth from February to November, offered good potential for complementing the- summer growth of lucerne. Irrigated and dryland farmlets were established with Wairau lucerne, and

stocking rate of 27 ewes per hectare (11.2 ewes per acre) but lambing had to be delayed to late September to gain enough feed for lambing. Consequently with late lambing, most of the lambs had to be fattened after Christmas which proved difficult. At these high stocking rates, lambs are forced to graze more stem, with a subsequent drop in nutritive value and rate of growth. With this protracted lambfattening period subsequent difficulties were experienced in gaining sufficient feed for the ewe mating period such that it would have been difficult to sustain that high stocking rate if the research had been continued for much longer. By 1977 we had, therefore, concluded that the lucerneTama system proposed too many practical difficulties for it to be used long-term in a viable farming operation. We, therefore, returned to the concept of perennial grass-lucerne systems. A change was made to include a perennial rj'egrass component in the irrigated system to reduce the depend-

ence on hay and to provide an alternative feed at mating to preclude the oestrogenic effect of grazing lucerne at this time. This system would also allow earlier lambing from the earlier growth of the grasses and thus lambs would be able to be finished earlier. Paddocks with Matua prairie grass and lucerne, Maru phalaris and lucerne, and Nui ryegrass and white clover were added to the system with the stockingrate adjusted to 22 ewes per hectare. This was likely to be more sustainable stockingrate than the 27 ewes per ha of the previous system. However, as new lucerne

cultivars, Rere and other varieties, appeared about this stage it was unrealistic to continue the work in detail with outdated lucerne varieties. The potential of the perennial grass system was likely to approach the 480 kg mea't per hectare and to be sustained, but the more simple Nui-Matua system at Lincoln had begun to re-affirm the role of irrigated ryegrass pastures by the time the trial was underway, and the work was halted. In summarising, it has been shown that the characteristic of Nui to respond rapidly to autumn rain can

be capitalised upon by using' irrigation, thus giving very high levels of production. Dryland lucerne (especially the new varieties) still has an important role to play. In completing this series of research trials, it is appropriate to acknowledge the considerable co-operation of Mr and Mrs Williams and of the Malvern County Council in allowing us to use water for irrigation. We believe that the data obtained can usefully contribute to public awareness of what are the biological advantages of using irrigation in Canterbury.

Lamb meat production attained in Grasslands Division research at Kirwee Stocking Rate % lambing Calculated meat/ha Index Dryland Ruanui 13/ha 135 233 100 Nui 13/ha 138 225 98 Dryland Lucerne/Tama 17/ha. 125 300 129 Irrigated Lucerne/Tama Lucerne/Tama/ 27/ha 130 480 206 Perennial grasses 22/ha 134 390 167 Irrigated * Nui/Matua * On Templeton soil at Lincoln. 20/ha plus 5 hoggets for replacement 195 563 240