Conference Papers

Now showing 1 - 4 of 4

The effect of planting date on maize: Silage yield, starch content and leaf area
(2014) Tsimba, R; Edmeades, GO; Millner, JP; Kemp, PD; Morris, NJ
Four field experiments were established in the Waikato and Manawatu regions over two years to determine planting date (PD) influence on growth, silage yield (SY) and starch content of seven maize (Zea mays) hybrids. Silage yield response to PD was best described using quadratic regression models. The PD at which silage yield was maximised (optimum PD) was later in the cooler, high latitude environment of Manawatu (23 October) than the more northerly locations in Waikato (9-15 October). In both regions, planting 2 or 3 weeks either side of the optimum PD reduced SY by <5%. In Waikato, the optimum PD in a warmer than average spring (+1°C) was 1-2 weeks earlier. Under non-limiting moisture conditions later planting reduced yields in both Waikato (24.22 versus 21.06 t/ha) and Manawatu (30.09 versus 22.50 t/ha). This was attributed to decreased temperatures (<15°C) and radiation (<17 MJ/m2 /d) during grain filling. Due to more rapid reductions in autumn temperature and radiation in Manawatu, yield decline beyond the optimum PD was greater (-183 kg/ha/d (0.6%), R 2 =0.81) than Waikato (-50 to -85 kg/ha/d (0.3%), R 2 ≥0.67). Starch content was highest for plantings before 6 November, dropping thereafter with harvest index. Highest maximum leaf area index was observed at mean daily temperatures of 17-19°C.
Are root exudation or rainfall on treated plants likely causes of pasture damage after wiper application of herbicides?
(Weeds Society of Western Australia, 11/09/2016) Harrington, KC; Ghanizadeh, H; Moyo, C; Kemp, PD; Eerens, JPJ; Randall, R; Lloyd, S; Borger, C
Wiper application of herbicides to weeds sometimes causes damage to pasture plants, especially white clover, growing immediately under the wiped weeds. Two experiments were conducted to determine the potential for either exudation of herbicide from roots or rainfall washing herbicide off treated plants to cause damage to white clover after wiper application. In Experiment 1, Californian thistle and white clover were grown in the same pots within a glasshouse, then either metsulfuron or a triclopyr/picloram mixture were applied to the Californian thistle using a Rotowiper. White clover growing in pots below treated plants was significantly affected by the metsulfuron but not the triclopyr/picloram mixture, when compared with the untreated control plants. In Experiment 2, Californian thistle, white clover and perennial ryegrass were grown in separate pots within a glasshouse. Glyphosate, clopyralid, metsulfuron and a triclopyr/picloram mixture were applied to Californian thistle plants using a Rotowiper. The treated Californian thistle plants were then exposed to artificial rain from a rainfall simulator either 1 or 5 days after herbicide treatment, with pots of white clover and perennial ryegrass positioned under each Californian thistle plant during the rainfall event. All of the herbicides except glyphosate significantly affected white clover for both rainfall events, whereas only metsulfuron significantly affected perennial ryegrass for the Day 1 washing. Thus although damage from herbicide exudation does appear possible, rainfall following wiper applications is probably more likely to cause damage to clover growing under treated plants.
Effect of 10 years of organic dairy farming on weed populations
(2012) Harrington, KC; Osborne, MA; Kemp, PD
To determine whether converting to organic farming increases weed problems, a trial at Massey University in New Zealand split a dairy farm in half, with one half farmed conventionally for 10 years and the other half farmed using organic principles. Weed populations in selected paddocks of each farmlet were studied for 8 years to determine how these populations would differ between the two systems. After 10 years, weed problems differed little between the two farmlets. Both still had broad-leaved dock (Rumex obtusifolius L.) and hairy buttercup (Ranunculus sardous Crantz) as their main weed species. Weeds were most noticeable in pastures in the year following regrassing activities for either farmlet, but being unable to use glyphosate during seed-bed preparation or use selective herbicides after sowing of new swards, meant weeds were sometimes worse in organic pastures after resowing than in conventional pastures. These weed problems were dealt with over the first few years after resowing by good grazing management, and ensuring pastures were dense once the annual species hairy buttercup had flowered and died, thus minimising any further establishment. Re- sults from the trial suggest that weeds need not be an impediment to organic dairying.
Improved extension practices for sheep and beef farmers
(New Zealand Grassland Association Occasional Publication, 14/04/2016) Gray, DI; Sewell, AM; Hartnett, M; Wood, BA; Kemp, PD; Blair, HT; Kenyon, PR; Morris, ST
Innovation is critical for maintaining New Zealand’s competitive advantage in agriculture and central to this is farmer learning and practice change. Despite the importance of farmer learning, limited research has been undertaken in New Zealand. In this study, an extension programme was developed based upon educational theory and research and then evaluated over a 3 years to identify the factors that were important for farmer learning and practice change. This paper provides a brief overview of findings of a 3 year interdisciplinary study conducted at Massey University with 23 farmers that investigated the critical factors that support farmers’ learning. The five critical success factors and the seven educational principles identified from this study provide guidelines for how science should interact with farmers to foster effective innovation. These findings are also applicable to other extension approaches such discussion groups, monitor farms and sustainable farming fund initiatives where farmers work with scientists and/or rural professionals.

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