Fifty years of sustained investment in research and development has left the Australian cotton industry well placed to manage nitrogen (N) fertiliser. The average production in the Australian cotton industry today is greater than two tonnes of lint per hectare due to improved plant genetics and crop management. However, this average yield is well below the yield that would be expected from the amount of N fertiliser used. It is clear from the recent studies that across all growing regions, conversion of fertiliser N into lint is not uniformly occurring at application rates greater than 200-240 kg•hm − 2 of N. This indicates that factors other than N availability are limiting yield, and that the observed nitrogen fertiliser use efficiency (NFUE) values may be caused by subsoil constraints such as sodicity and compaction. There is a need to investigate the impact of subsoil constraints on yield and NFUE. Gains in NFUE will be made through improved N fertiliser application timing, better targeting the amount of fertiliser applied for the expected yield, and improved soil N management. There is also a need to improve the ability and confidence of growers to estimate the contribution of soil N mineralisation to the crop N budget. Many Australian studies including data that could theoretically be collated in a meta-analysis suggest relative NFUE values as a function of irrigation technique; however, with the extensive list of uncontrolled variables and few studies using non-furrow irrigation, this would be a poor substitute for a single field-based study directly measuring their efficacies. In irrigated cotton, a re-examination of optimal NFUE is due because of the availability of new varieties and the potential management and long-term soil resilience implications of the continued removal of mineralised soil N suggested by high NFUE values. NFUE critical limits still need to be derived for dryland systems.
Before dealing with the marketing of livestock I will mention briefly the current arrangements for the disposal of our two main livestock products—milk and eggs. Milk is marketed through a Producers’ Marketing Board which operates on very much the same lines as the Milk Marketing Boards in Great Britain.In the marketing of eggs we have a unique system for the control of egg quality. The eggs are collected in the normal way by packers, or collectors acting on their behalf, and are graded on a quality basis in the packer’s store. The producer is paid on the result of this grading, deductions being made for second quality eggs, cracked eggs, soiled eggs, etc. The grading and packing are supervised by officers of the Ministry of Agriculture who also carry out further checks on the standard of packing and quality of eggs being shipped to Great Britain. These further checks are carried out at the ports of shipment, random samples of eggs being subjected to further quality tests.
Context Predicting the nitrogen (N) mineralisation from soil organic matter is a key aid to fertiliser decision-making and improving the N fertiliser use efficiency of a crop. Aims and methods Field experiments were conducted to assess the amount of inorganic N derived from soil organic matter mineralisation over two seasons (2017–2018 and 2018–2019) across treatments differing in irrigation frequency and amount. During both seasons, the plant line soil in each treatment was sequentially sampled at each irrigation event. Key results There was an effect of the soil water deficit on the measured accumulated soil inorganic N derived from mineralisation in both measurement years. It was observed that soil inorganic N accumulated in the plant line rather than in other hillside and furrow positions for all soil moisture deficit treatments in both years. In 2017–2018, N accumulated in the plant was significantly greater than the measured accumulated inorganic N (0–300 mm). Conclusions and implications The sequential soil sampling approach was challenging in irrigated systems and we propose a hybrid measurement of pre-season available soil N and/or plant N uptake in nil N fertiliser plots as a means of estimating N derived from soil organic matter mineralisation.
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