26 IREC Farmers' Newsletter No. 199 — Autumn 2018 Stomp showed excellent activity on grasses, while Terbyne showed suppression only of barnyard grass but it controlled fleabane well. Eric stressed that farmers should follow the ‘2 + 2 & 0’ rule, which simply means: l  use 2 NON-glyphosate weed control options in fallow/winter crop l  use 2 NON-glyphosate control options in cotton l  ensure there are 0 survivors, i.e. weeds do not set seed and replenish the soil seed bank. Many weed seeds are short lived in the soil, so two to three years of zero seed set will eliminate problem weeds. Eric undertook a weed study tour in the US in 2017 and concluded his presentation at the field day with key lessons learnt from the tour. These were to retain pre-emergent herbicides as part of weed management strategies and to implement a residual and layby strategy so that glyphosate is not doing all the heavy lifting. Regulating cotton growth Steve Buster, Cotton Research Officer with NSW DPI, is investigating the impact that growth regulants have on fruit shedding and yield in cotton. Part of the challenge of growing cotton in the southern region is getting early growth from the plant while temperatures are still cool. Accumulated temperature influences plant/crop phenology, i.e. the timing of growth of leaves, squares and flowers. Plant hormones are also involved in growth stimulation, so the use of applied plant hormones (growth regulants) may be a way to encourage the cotton plant to grow in spite of cooler temperatures. Research in the USA in the 1990s had positive results in promoting plant growth from applications of a proprietary mix of plant growth hormones. One of Steve’s trials at the IREC field station uses a mixture of the plant hormones, gibberelic acid (GA3), indol-acetic acid (IAA) and cytokinin to promote early plant growth. The mixture was applied at sowing, first square and first flower. Data is still being collected as to the effectiveness of applying these hormones. Other plant hormones can be produced by the cotton plant in times of stress, such as ethylene. In good growing conditions the cotton plant produces ethylene to ripen bolls. But in times of stress, ethylene can also cause the plant to shed squares and bolls when the plant ‘thinks’ it cannot hold all the fruit it has. Stressors such as extreme temperature (both high and low), cloudy weather and waterlogged conditions can induce the production of ethylene in the plant, which then promotes fruit shedding. A second experiment conducted by Steve at the IREC Field Station is looking at various application rates and timing of applications of a product that inhibits the production of ethylene in the plant. It is hoped that by inhibiting the production of ethylene, the plant will hold more fruit and thereby increase yield. Data and results are still in the process of being collected. Predicting yield Kieran O’Keeffe spoke about remote sensing using drones and VARIwise software for yield prediction of cotton at the field station. This system was trialed last season with yield prediction proving quite accurate. For the 2017–18 season, the plan is to fly the area every two weeks from late January until picking, in order to determine the rigor and reliability of both the remote sensing equipment and the software. If available early in the season, a reliable system for yield prediction would enable growers to make more timely management and marketing decisions, with greater returns being the ultimate outcome. Reporting and continuation When the field day was held, 18 January 2018, the cotton crop was at the 20 nodes stage. The crop was growing well and good yields are anticipated. Results from all the trials and projects at the IREC Field Station will be available after picking and ginning, and there are plans to continue each of these projects next season. Acknowledgement I would like to acknowledge and thank Wendy Quayle, Emma Ayliffe, Eric Koetz, Steve Buster and Kieran O’Keeffe for running the trials at the IREC Field Station, contributing material presented at the field day and supplying information used in this article. Further information Iva Quarisa T: 02 6963 0936 E: [email protected]