Following the establishment phase of the Smarter Irrigation for Profit project, a Rural R&D for Profit initiative, participants identified that one of the key barriers to farmers using scheduling tools is the diversity of tools available, each with its own strengths and weaknesses, they expressed a need for a simple resource that could assist farmers and extension officers in the selection of an appropriate irrigation scheduling tool or tools for their needs. This project aimed to provide a summary of a range of irrigation scheduling tools that have been reviewed, tested or utilised by Smarter Irrigation for Profit participants.

Experience on the ground also found that if scheduling tools are to be adopted by industry, they need to be simple — simple to install, setup, use, interpret and respond to. Many of the tools tested required significant effort to learn how to use appropriately so as to achieve any potential benefit. Providing a simple way to compare and consider a range of tools to enable the selection of a suitable tool was proposed as the basis for this document.

It is envisaged that this resource will provide a starting point for others who need to review tools prior to implementing them on farm. This project is not endorsing any particular product. Any appropriate tool will need to be considered for the circumstances in which it is to be used.

Irrigation Scheduling

Crops that are kept within acceptable stress limits during their growth cycle have the potential to produce optimum yields of high quality. The aim of irrigation scheduling is to keep soil moisture within a desired range, usually between field capacity (full point) and a predetermined refill point for optimal growth.

The irrigation management decision-making process involves deciding “how much” to irrigate, at “what position” in the field, and “when” to irrigate by considering:

* the current water content of the soil

* the current rate of crop water use.

* the soil’s readily available water-holding (RAW) capacity and refill point

* the application rate (millimetres per hour) of the irrigation system. This allows the calculation of how many hours are needed to apply the required amount of water (in millimetres).

* the evenness of water application (uniformity) and efficiency of the irrigation equipment in your field

Irrigation scheduling tools seek to assist farmers to make informed decisions with either the current water content of the soil, the rate of crop water use, or both.

As a result the range of scheduling tools can be grouped into those that monitor the soil water content, those that use weather data to estimate how much water the plant has been consuming, and those that monitor the plant for water stress.Experience has shown that using multiple methods to assess the amount and timing of irrigations can improve scheduling decisions. The ability to manage and interpret data has improved considerably, and some scheduling tools are now combining a range of soil and plant data into one software platform in order to improve the ease the process of making irrigation scheduling.

This project provides a summary of tools used by participants in the Smarter Irrigation for Profit project grouped on the basis of measuring:

* soil water content

* weather based crop water use

* plant stress

* combinations of those above

Combination tools include the growing number of software delivery platforms that can connect to a range of different sensors and deliver data to web connected devices for growers and advisors.

This review has not sought to be comprehensive and cover every available tool, but instead focusses on those that have been used by participants in the Smarter Irrigation for Profit project. The following details the list of tools that have been included in this document. The project is not endorsing any particular product. Any appropriate tool will need to be considered for your own circumstances.

This funding supported the tour of a number of southern irrigators as part of the Maximising On-Farm Irrigation Profitability project, a sub-project under the Smarter Irrigation for Profit project. A group of irrigators from southern NSW and northern Victoria travelled to the Gwydir Valley to attend the Gwydir Valley Irrigators Association annual research field day as well as visit other irrigation properties and the ACRI/CSIRO Research site. The impact of the tour was immediate, both providing networking opportunities for growers of the north and south and providing exposure to new precision irrigation systems technology.

Cotton production in Australia is limited by the lack of water availability in most years. This project aimed to enable growers to adapt and tailor their irrigations to an uncertain future climate and water availability situations based on definitive data to manage risk. Earlier research supported by the CRDC enabled developing an irrigation scheduling method for furrow irrigated cotton based on canopy temperature monitoring. Through being strongly related to soil water availability, canopy temperature measurements enable continuous monitoring of a crop’s requirement for irrigation using a plant-based method that is practical to use on commercial farms. Through this project the canopy temperature method was further refined for fully irrigated systems and its use tested in partially irrigation situations. The three key areas of research for this project were:

1. Integrated Irrigation Agronomy for High Yielding Systems:

To achieve the highest yields the irrigation management of the crop needs optimizing through the entire crop development period. We conducted detailed research trials at the Australian Cotton Research Institute (ACRI) near Wee Waa (NSW) to optimize irrigation strategies at planting and during early, mid and late season which are explained below:

We conducted a comparative investigation of pre-watering and watering up at the ACRI to determine the best irrigation strategies for crop establishment. Watering up one day after planting resulted in slower germination and 25% less plants established compared with the crop pre-irrigated a week before planting. Soil temperature in the watered up treatment was up to 2.4 °C cooler than in pre-watered soil which most likely affected germination and establishment. These results are important in that there was only one cold shock (i.e. minimum air temperature <12 °C) during this trial in 2015-16 season compared with 20 and 10 cold shocks in the following two years, respectively, yet plant establishment was affected. It is important to consider these effects of watering up in cotton and, where watering up is unavoidable because of other farm factors, planting time may be adjusted to avoid cooler soil temperatures.

The timing of first in-season irrigation (excluding at planting) drives the establishment of a plant with sufficient vegetative growth to support high yields. Bollgard® varieties with high fruit retention may benefit from vigorous plant growth translating into high yields. A trial conducted at ACRI during 2015-16 to optimize the timing of first irrigation did not generate the expected treatment differences in plant development and yield because of wet weather conditions. It was identified that thermal cameras can be an effective tool for monitoring plant water stress during early season when canopy temperature infrared sensors cannot be used because of smaller canopy.

Timely application of mid-season irrigations is most important in terms of its effect on yield. In practical situations most cotton farmers may have to make an irrigation decision few days in advance. We investigated integrating canopy temperature and short-term weather forecast to make an irrigation decision five days in advance. Irrigations were planned in advance by either using an average daily stress time value based on historic data (treatment 1), or applied earlier or later than the predicted date based on short term weather forecast using dynamic deficit approach (treatment 2). Both the treatments underestimated the canopy temperature stress time compared with the measured observations. It was concluded that an irrigation decision

made in advance should be based on canopy temperature that is predicted from short term weather forecast rather than historical climate data.

Detailed trials were conducted at the ACRI to optimize the timing of last irrigation using canopy temperature sensors in a fully irrigated cotton system. The results showed canopy temperature sensors can be used for scheduling last irrigation with a need for further testing in different weather conditions to build confidence in the results.

2. Irrigation scheduling with limited water

We conducted detailed trials to develop irrigation decision frameworks in limited water situations to limit the risk and seasonal variability. The utility of canopy temperature sensors was investigated in partially irrigated systems with three different row configurations commonly used in cotton industry. There were strong relationships between yield and canopy temperature (and its derivatives) in all row configurations. As canopy temperature is affected by a plant’s access to (or lack of) soil water, regardless of location of water within soil profile, this method may help improve irrigation scheduling in partially irrigated systems where different row configurations are used. We tested applying a single irrigation during flowering at canopy temperature stress thresholds higher than that used in fully irrigated systems. In the years we conducted these studies we could extend/delay our irrigations with little impact on yield and yield gains in one instance. Further research will be needed to understand how we can best utilize our ability to better quantify stress (using canopy temperature sensors) in years that are dissimilar to those experienced in this study to manage risk in limited water situations.

3. Research Support for high impact delivery and adoption

Research support was provided in collaboration with the Cottoninfo team through on-farm trials and field days. On-farm trials were conducted in different cotton growing valleys in New South Wales (Wee Waa, Rowena, Walgett) and Queensland (Emerald, St. George), where farmers integrated the canopy temperature approach in their irrigation decision making. The overarching philosophy of these trials was to provide farmers the opportunity to integrate different tools for making an irrigation decision. Trials in Emerald and St. George resulted in saving at least one irrigation on both farms using canopy temperature sensors without impacting yield. This research enabled farmers to use an irrigation scheduling tool that is based on real-time monitoring of a crop’s need for water. A commercial partner has been identified to extend canopy temperature approach of irrigation scheduling to the Australian cotton industry.

Some important future research areas are: 1) Utility of plant-based method of irrigating such as canopy temperature for optimizing crop water use efficiency from the perspective of less water use; 2) capturing spatial variability on large farms with canopy temperature sensors, and/or how many canopy sensors per farm are required to make the best irrigation decisions? 3) Continuing research on utility of canopy temperature sensors in partially irrigated systems, and 4) Utility of thermal images in assessing crop stress during early cotton season.

This project was funded by the Department of Agriculture and Water Resources, and the Cotton Research and Development Corporation through Rural R & D for Profit program.

Grower-led irrigation system comparison in the Gwydir Valley aims to collect commercially relevant comparative data on different irrigation systems. There were two parts to this project, an irrigation system comparison and an implications for capital investment, management and the resource requirements (water, energy and labour) associated with different cotton irrigation systems and new technologies. Incorporated into this is the adoption of automation technology and different approaches to farming systems.

The CSIRO breeding program at the Australian Cotton Research Institute at Narrabri aims to develop locally adapted varieties for use by Australian farmers. The program has been very successful in developing varieties for all cotton growing areas with ten conventional and five INGARD varieties (the latter subject to regulatory approval) available through Cotton Seed Distributors (CSD) for 1996 planting. The products of the breeding program have brought many millions of extra dollars to farmers and have been vital in maintaining the strength of the cotton industry. Key advances from the CSIRO breeding program include the development varieties with okra leaf (for insect and mite tolerance), better disease resistance (particularly bacterial blight and Verticillium wilt), improved fibre quality and good adaptation to cool growing areas. For 1996 planting CSD have available two very promising new CSIRO varieties -Sicot 189 and Siokra S-101.

Weed management systems in cotton are continually evolving, particularly in response to reduced cultivation and chipping and increased use of herbicides. The use of permanent beds and reduced tillage is likely to cause a shift in the problem weed spectrum, towards perennial weeds and those with rhizomatous root systems, which have previously been controlled with cultivation. A survey of 23 properties found that most weeds were much worse on fully cultivated fields than permanent bed fields. The exceptions were rhyncho, datura, nutgrass and polymeria, which were much worse on permanent bed fields. These data support the use of permanent beds as a way of reducing over-all weed pressure, but emphasise the need to .develop control strategies targeted at perennial and rhizomatous weeds.

Fungal diseases, in particular Verticillium wilt, and, more recently, Fusarium wilt, have the potential to cause major losses in Australian cotton production. Research conducted by our group is focussed on genetic approaches to the improvement of cotton resistance to fungal attack.

A new project at Narrabri aims to develop methods of breeding cotton varieties that per/ orm better under dryland and limited water situations.

The cotton monocultural system in most of the production areas in Australia strongly discriminates against natural enemies and favours the development of pest outbreaks. Pest outbreaks in monocultural systems occur because insect predators and parasitoids usually have more complex food requirements than Helicoverpa and most other phytophagous insects. The latter usually mate and oviposit without any feeding, relying only on reserves transferred from their larval food whereas predatory insects and parasitoids require different sources of food in larval and adult stages to develop and survive through the season. Thus pests like Helicoverpa can rapidly infest crops through migration and lay their eggs with little opposition from natural enemies. To solve this problem the cotton system should be diversified by interplanting cotton with other crops. The alternate crop could serve as a refuge to beneficial insects. Crops like safflower, sunflower, sorghum, corn, tomato and Lucerne have been studied for the past 4 years and Lucerne was found to be suited for the cotton production system. We report here studies to integrate lucerne into the Envirofeast IPM program to serve as a refuge for beneficial insects.

The Australian cotton industry is at the dawn of a new age in cotton production: an age where most, if not all, of the cultivars in use will carry the products of gene technology. The expected release of INGARD cotton this season is specially satisfying to us as the beginning to the early promises of genetic engineering for cotton improvement. While the task is nowhere near completed, the first commercial release of a transgenic cotton plant represents a concerted effort on the part of the industry&#39;s researchers, research collaborators, seed producers, consultants and growers to provide the industry with a new product that will significantly reduce chemical pesticide usage. INGARD cotton should be followed in rapid succession by a variety of new cultivars with enhanced production attributes that together will revolutionise the way you grow cotton.