The current status of nitrogen fertiliser use efficiency and future research directions for the Australian cotton industry

Abstract

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.

Yield Response, Quality Traits, and Nitrogen-Use Efficiency of a Burley Tobacco Crop Grown in Mediterranean Areas (Southern Italy) as Affected by Intensive N Management

“…Nowadays, the priority goal of modern and sustainable agriculture is to reduce N losses to the environment; this result might be reached by improving the efficiency of N use [8,9]. Several research studies were carried out in the last 20 years to investigate N-use efficiency of many crops such as maize [10][11][12], wheat [13][14][15][16][17][18], tomato [19][20][21][22][23], potato [24][25][26], sunflower [27][28][29], industrial crops [8,30,31] or non-edible and biofuel crops [32]. All of them are currently fertilized with a high amount of N. Various Nuse indexes were proposed, generally measuring both N fertilizer efficiency (yield/N apply) or crop N efficiency.…”

Machine Learning Optimised Hyperspectral Remote Sensing Retrieves Cotton Nitrogen Status

“…It's been widely reported for decades that nitrate leaching into the groundwater [5] and emission as oxides into the atmosphere [6] cause extensive local and global environmental damage, with, for example, intensive agriculture in the USA contributing to~400 hypoxic zones in coastal marine ecosystems from farms upstream [7]. Within the cotton industry, lint yields have increased through improved plant genetics and management, however, there is a need to investigate ways to improve nitrogen use efficiency as yield quantities are not uniformly responsive to the high levels of N applied [8]. By identifying N concentration spatially across a cotton crop the factors influencing N use efficiency can be studied, leading to more tailored N management strategies.…”

Predicting within‐field cotton yields using publicly available datasets and machine learning

“…However, this is a time‐consuming, labor‐intensive, and spatially restricted method. By the time stage bolls begin to develop, the implementation of any in‐season management, such as N fertilizer applications, is going to be too late to impact yield (Macdonald et al., 2018), particularly when current N fertilizer applications occur between the squaring and flowering growth stages (CRDC & CottonInfo, 2018).…”