Research and trials on the real cost of N application

Ginning update, MyBMPVerticillium wilt, Volunteer cotton trials soil health workshops, Reniform nematode rotation trial at Theodore

Latest weather news Observed rainfall analysis (for the week ending 14 Dec): Summary of climate indicators: Rainfall and temperature guidance summary: Madden-Julian Oscillation (MJO): Australian Sea Surface Temperatures: El Niño-Southern Oscillation (ENSO) outlook for 2015

First irrigation timing, Researchers and consultants thoughts

Latest weather news: Rainfall analysis (for the month of November): Tasman Sea Atmospheric Blocking ; Summary of climate indicators; Rainfall and temperature guidance summary; Madden-Julian Oscillation (MJO); Australian Sea Surface Temperatures

Spider mites are small arthropods that feed on the underside of cotton leaves using their piercing mouthparts to suck out the contents of leaf cells. This removes chlorophyll from the leaves and causes a reduction in photosynthesis. There are three types of spider mites twospotted spider mites (the main pest species; pale green with two distinct dark green spots on either side); bean spider mite (red in colour) and strawberry spider mite (pale green with three dark green spots on either side). They all cause different amounts of damage, so correct identification is important to help you make the correct control decision.

A knowledge system model to improve the effectiveness of the transfer of(irrigation)

information to growers was developed and tested. Knowledge can be described as

information combined with experience, context, interpretation, and reflection. A frequent

misconception is to equate it with information. The knowledge system depends on the way

in which information is applied. Industry extension programs need to facilitate opportunities

for knowledge sharing and transfer. This is significantly more complex than typical irrigation

extension programs. The central feature of the model was to employ more of the five

extension models rather than only the two commonly used. The main vehicle was the

concept of cohesive, self-directing groups that form the core around which activities under

the other models are conducted. This was achieved by production of an innovative Cotton

& Grains Irrigation Workshop Series containing 7 modules; establishment of a pathway for

accreditation in irrigation management; development of a model for delivering commercial

irrigation services; production of a range of information resources; creation of a dedicated

irrigated cotton and grains web site.

Drip irrigation/fertigation (“advanced fertigation”, “open hydroponics”) is being adopted by

the Australian citrus industry. Hardware sophistication and the complexity of management

regimes being used vary enormously; from old paradigms applied using modern equipment,

through to approaches used overseas, but untested under Australian conditions. Generally,

these technologies are being adopted without support. This project aimed to address

knowledge gaps and test assumptions regarding the application of modern approaches to the

delivery of water and dissolved mineral fertilisers to citrus trees under Australian conditions.

Seedling rootstocks growing in sand culture were used to investigate the impact of variations

in nutrient solution composition. Relative vigour of the rootstocks was maintained

irrespective of nutritional treatment. The rootstock genotypes differed in their rate of

response to increasing N supply and the efficiency with which N was used in the shoots. The

most vigorous rootstock responded to small increments in N supply and achieved maximum

growth with lower tissue N than less vigorous rootstocks. Across all rootstocks, more than 45

mg N/L in the nutrient solution conferred no additional advantage. Further, optimum

potassium concentration appeared to be around 23 mg/L. Neither shoot biomass production

nor macronutrient accumulation were advantaged by acidification of the nutrient solution.

Some aspects of modern irrigation/fertigation practices were compared using young navel

oranges at Dareton. Similar amounts of water and fertiliser were supplied in either a “best

practice” approach or an “open hydroponics” approach. The strongest influence on tree

behaviour was season. Neither irrigation nor fertiliser management influenced tree behaviour

to any great extent. The composition of soil solutions was extremely variable. Despite best

practice ETo scheduling, high concentrations of N in the irrigation water resulted in a gradual

movement of NO3

- down the soil profile. In a fertigation program based on reduced and

oxidised forms of N, nitrate-N greater than ~34-45 mg/L was clearly in excess of the roots’

ability to take up NO3

- Water and solute movement in lysimeters was quantified and compared to field

measurements. Various scenarios were explored using a 2D/3D water and solute

movement model (“Hydrus”) that evaluated NO3

- movement under different fertigation application patterns, involving pulsed and non-pulsed irrigation, and variable timing of fertigation applications across the daily irrigation pattern. The simulations suggested that injection of NO3

- into the irrigation water in the early or middle pulses of daily irrigation resulted in less NO3

- being retained in the rootzone for uptake by tree roots, and concomitant greater leaching losses than application of fertigation in the later part of irrigation pulses, or at a low level across the whole day.

The application of modern fertigation strategies is unsupported by objective public-domain

data, and the long term impact of such strategies under Australian conditions is unknown. A

field site was established to quantify the long term responses of three selections of navel

oranges on five different rootstocks to fertiliser delivered using modern delivery technology.

The site will serve as a research and technology transfer resource well into the future, and is

probably unique in the world. Industry support in the future will be needed to take full

advantage of the potential benefits of this site.

Two Excel spreadsheet-based decision support tools were developed to assist irrigators to

make more informed decisions regarding irrigation scheduling and fertilisers use. One of

these, E-Schedule, an irrigation scheduling decision support tool, was developed to make it

simpler to bring together all the disparate pieces of information, including weather

predictions, needed to make informed irrigation scheduling decisions. E-Schedule has

nationwide applicability.

Latest weather news Observed rainfall deciles (for the month of October): The Southern Annular Mode, Summary of climate indicators; Rainfall and temperature guidance summary; What sort of monsoon can we expect this summer?

Deep drainage and runoff, combined with poor nitrogen fertiliser practice, is resulting in significant nitrogen losses in early season irrigation. Currently 33% of growers are applying over 300kg N/ha, with research showing as little as 20% of this being taken up by the plants (Grace 2016). In an effort to keep the dialogue between researchers and growers active in the face of increasing nitrogen fertiliser costs and the industry need of responsible nitrogen management, CottonInfo established trials during the 2017/18 season quantify the runoff component of the nitrogen loss pathway and highlight the relationship between irrigation and nitrogen management.

Boosting the nitrogen use efficiency of cotton farms within Australia is a key objective of the Australian cotton industry. The movement of nitrogen with irrigation water has been anecdotally found by many growers with differences in crop growth and yields along the length of the field, from head ditch to tail drain. Nitrogen is also lost from the field through deep drainage and runoff totalling more than 10% of the applied N (MacDonald 2017). Both factors are influenced by irrigation management. Additionally, it has been highlighted through experiments in the Upper Namoi region by Baird (2016) that losses of 20 to 30 kg of pre-applied N can occur in the first irrigation alone. In the same study it was also found that irrigation intensity also affected Water Use Efficiency (WUE) and NUE.