Legume content of pastures in agroforestry systems
Abstract
White clover (Trifolium repens; cv. Demand), red clover (Trifolium pratense; cv. Pawera), subterranean clover (Trifolium subterranean; cv. Dalkeith, Karridale and Denmark) and Caucasian clover (Trifolium ambiguum; cv. Endura), were evaluated in a cocksfoot (Dactylis glomerata; cv. Wana) pasture in full sunlight and under 60% shade on Templeton silt loam of medium fertility at Lincoln University, Canterbury. Wana cocksfoot and the four clover species were sown in March 1995, in plots that were 6 x 8 m in size. The clover comparison experiment is a randomised complete block design, which was replicated three times. In this experiment, each clover mainplot had two subplots: full sunlight and shaded pasture created by placing two 1 x 1.5 m cages over matching areas in the main plot. Shade treatments were established on 15 September, 1996 with the first harvest occurring 27 days later on 11 October. Subsequent harvests on 20 November, 16 December and January 14 1997, had 24-30 days of growth between harvests.
Lower light intensity resulted in a reduction in mean daily pasture production from spring to mid-summer under shade of 8.8 g DM/m2 compared with 9.3 g DM/m2 in full sunlight. Through the duration of the experiment, total pasture production was reduced by 6% with shaded pasture production coming to 964 g DM/m2 compared with 1018 g DM/m2 in full sunlight. In the early stages of the experiment, the dry matter production of Wana was reduced under shade by 3-12%. However, in midsummer, dry matter yields increased under shade by 3-69%. The effects of shade on clover yields were more pronounced, with reductions in yields of 43-67%. Wana dominated, particularly under shade, where clover content was 10%, compared with 20% in full sunlight. Under shade, Wana increased in height by 25% and clovers by 15%. Increases in height and a reduction in vegetative tiller population by 26% under shade, led to reductions in Wana and clover density. In early/mid spring, subterranean clover excelled over other clovers with yields of 88 g DM/m2. Red clover production was greatest in mid-summer.
A supplementary study on the effects of sheep urine on the performance of Wana cocksfoot and white clover found that dry matter production of Wana increased by 54%, while white clover yields decreased by 56%. Increases in the height of Wana (311 mm) and reproductive tiller population (326/m2) occurred in urine patches. Reductions in forage digestibility were found in urine patches, while N% increased in Wana increased.
At the Lincoln University Agroforestry Trial, minimal differences were recorded between understorey and open pasture total dry matter production in summer, while pasture yields in urine patches increased by 59%. Wana yields did not decline, while clover yields were reduced to 0.8 g DM/m2 in the understorey compared to 8.7 g DM/m2 in open pasture. Increased grass heights were recorded in the understorey (247 mm) and urine patches (284 mm). Vegetative tiller populations decreased in the understorey by 33%. Increases in organic matter and dry matter digestibility and nitrogen content of Wana were recorded in both urine patches and the understorey. These findings suggest that the performance of clover in silvopastoral systems will be seriously impaired due to increased competition for sunlight by the presence of Pinus radiata and Wana cocksfoot.
