Increasing competition on supply of fresh water for irrigation by agricultural, domestic, sports and industrial users demands water use efficient irrigation methods and compliance with environmental regulations. Drip irrigation (DI) and subsurface drip irrigation (SDI) are advocated for improvements in water use efficiency (WUE) and are increasingly being adopted by horticultural industries in Australia and overseas. Greater flexibility for automation and versatility of application of drip irrigation technology encourage wider-scale adoption by these industries. However, the higher initial investment for installation and lack of significant yield gains due to drip irrigation compared to conventional irrigation methods are somehow deterrents for broad-scale adoption.

Ways to optimise the use of DI and SDI will have multiplier effects on water savings for irrigation in agricultural and other industries and minimize environmental impacts associated with traditional irrigation methods. One of the significant areas where greater optimization of DI and SDI is realized is through the use of aerated water for irrigation (oxygation). Sustained wetting fronts around emitters associated with DI/SSDI impose hypoxia in the rhizosphere. This impedes root respiration leading to sub-optimal plant performance. As irrigation water exits an emitter, it purges soil pores of soil air (containing up to 20% by volume of oxygen) with water that contains less than 10 ppm oxygen, a quantity we have shown is used up quickly by roots and soil microbes. Rising soil temperatures, salinity, and soil compaction will exacerbate this effect, as may disease such as Phytophthora of pineapple. Plant roots and soil microbes require oxygen for respiration.

In soils with inadequate aeration the lack of oxygen results in reduced plant growth and diminished productivity for many reasons, including: reduced root growth and root size; reduced root ability to absorb minerals and water; reduced photosynthesis and plant growth due to stomatal closure; loss of soil N due to the in-activity of microbes; adverse changes in soil chemistry; increased susceptibility to disease, and an alteration of the balance and supply of plant growth regulators.

Aeration of the irrigation stream, a process termed ‘oxygation’, overcomes this constraint. Oxygation is a new innovation in irrigation technologies. Aerated DI and SDI by different methods, such as venturi for air injection, allows for the simultaneous application of water, air and other agro-chemicals directly to the crop root zone. Therefore, it can potentially improve crop yield and water use efficiency. Conventional irrigation methods such as flood irrigation have large inefficiencies due to run-off, drainage and evaporative loss. SDI can significantly improve the WUE over that of flood irrigation, and oxygation can significantly improve WUE of SDI.

Oxygation involves mixing air with water using a venturi and delivering via a surface or subsurface drip irrigation system. An oxygation system can be installed as part of a new SDI system or may be retrospectively fitted to any existing SDI system. A venturi air injector is installed within the pipeline and draws air directly into the water stream. A single venturi can be installed immediately after the pump outlet and the air distributed through the main line to sub mains and lateral drip lines, or a single injector may be fitted to the beginning of each drip line. The amount of air ingress depends on the pressure differential across the venturi and the motive flow through the venturi.

Mazzei or Netafim Air Injectors improve soil aeration by entraining air (in the form of micro-bubbles) into irrigation water. The added air improves growing conditions, increasing root respiration and microbial activity. These improved soil conditions have resulted in significant increase in yields. All NPSI funded project activities in this report utilized Mazzei air injectors.

System requirements include drip/subsurface drip irrigation, water flow must be 3.8 LPM - 30.3 LPM per drip line (for MI 384, 584 and 1583 injectors) and the terrain must be level to moderately sloped. We are also evaluating alternative approaches for super saturating irrigation water with air using twin vortex, oxysolver and Seair diffusing systems and plan researching benefits on furrow and sprinkler irrigation. We also present our research progress on diversifying the use of oxygation in landscape (lawn) and sports industries (sport grounds) to improve the WUE of these industries and to minimize the offsite movement of pesticides and nutrient from such hidden landscapes.

A number of controlled environments studies in pots and the glasshouse showed positive response to oxygation in medium and heavy textured soils. With this recent innovation of aerating the irrigation stream (oxygation), returns, yields and water use efficiencies (WUE) of SDI crops all increase (see Advances in Agronomy 88: 313-377 (2005)). This preliminary research clearly highlighted the opportunities of harnessing the potential benefits of oxygation for yield, quality and crop water use efficiency in Australian horticultural industries across diverse crops, soil types and irrigation water qualities. On large-scale field trials with SDI and surface drip, yield increases in cotton of 19% and in cucurbits of 12-60% were achieved, with significant improvements in product quality as measured by increase in ºBrix percentage of the fruit (sweetness). We have undertaken trials on heavy clays and lighter soils and for surface trickle under mulch, and trickle above the ground, showing positive and beneficial effects of aerated water irrigation. In this report we summarize the outcomes of oxygation research carried out by CQUniversity Australia in collaboration with Australian primary industries in a range of annual and perennial crops, and suggest the approach for large-scale adoption by irrigation industries in Australia.

Tendifferent crop industries (cotton, pineapple, lucernes, capsicum, strawberry, fig, table grapes, melons, vegetables and apricot), plus crops consultants and irrigation businesses in QLD were involved in testing the benefits of oxygation in field scale research. Data collected over 2- 4 seasons on yield and water use efficiency suggested that yield benefits of 4 – 19% were achievable with oxygation. Oxygation involves installation of an air injector (pressure differential venturi) in-line for mixing air with irrigation water. The installation cost of air injector can be AU$ 600-1000 per hectare depending on size of air injectors and requirements of accessories and fittings. Air injectors can be installed into new irrigation installations or retrofitted into existing drip irrigation systems.

The response to oxygation varies with crop and soil types, quality of irrigation water and type of drip irrigation. Horticulture industries in Australia span the range of these variables, therefore there is need for collaborative research, industry engagement and involvement of multidisciplinary research teams in the field of oxygation research to harness the full potential benefits of this technology to the industry.The project has resulted in significant benefits to cotton, with an average lint yield increase of 14%. Large cotton areas in Australia are furrow irrigated, hence, adoption of oxygation within the realms of existing cotton irrigation practices is currently limited. Future research is therefore suggested on use of aerated water with furrow irrigation, the primary method for irrigation of cotton. Increase in yield (6% in industry yield and 26% in total yield) and suppression of Phytophthora has been recorded on pineapple. In other crops (capsicum, strawberry, grapes) yield increases by 4-10% have been recorded. In apricot and fig the crop is still in the juvenile stage, and will be ready for harvest in 2012/2013 season only. Data will be collected from these crops beyond the funded project duration.

Oxygation as a tool delivers air into the crop root zone. Oxygen limitations can be significant in compacted, saline, and water logged soil, and with high BOD effluent irrigation water. Therefore, potential applications of oxygation can go beyond the improvement of water use efficiency and increased yields with ordinary drip and subsurface drip irrigated crops, into amelioration of other conditions that impede the diffusion of oxygen in the rhizosphere.Air within the irrigation water is a two phase flow fluid, hence, it imposes challenges for uniformity of air distribution along the irrigation line. This situation may be severe particularly when the drip irrigation is run over long row distances. Development of monitoring tools for measurement of air fraction and ways to minimize the heterogeneity of air bubbles distribution are currently underway. A number (7) of refereed journal articles have been published, postgraduate and undergraduate students have been involved (8), active collaboration with irrigation business, crop and irrigation consultants has been developed, and more field testing by independent crop consultants is underway, suggesting a gradual dissemination of the technology beyond the project timelines and resources. The following pictures highlight industries under collaboration for oxygation research in Queensland, Australia, showing diversity in terms of crops and focus in terms of soil aeration.

Attendance and presention of my paper on long-term cotton experiments and changes in soil organic carbon in Australian cotton soils at the European Geosciences Union (EGU) Assembly, Vienna, Austria. I presented results on changes in SOC in the long-term experiments being conducted at ACRI in fields C1, D1 and F6. Soil Organic Carbon(SOC) decreased with depth, with the exception of rotations that had standing or incorporated stubble, however there was no one rotation that stood out from the others. Differences between the experiments at ACRI reflected the fact that two had subsoil constraint while the third did not. Also, the starting level in SOC differed between the three experiments and this is reflected in the rate of change in SOC levels in the 0-30 cm depth over time. Including tillage resulted in a decline in SOC, while rotations increased SOC over time.

Final Report Executive Summary

The sustainability of crop production is a key issue for agricultural systems. Maintaining soil

biodiversity is important for promoting soil health and sustainable crop production. The root zone

is rich with microorganisms and nutrients. Soil type and agricultural management practices have

great influence on soil biodiversity. Mixed vegetation contributes to an increase in soil

biodiversity, while intense mono-cropping supports the growth of only a subset of soil microbes and

suggested to be causing a decrease in biodiversity. Furthermore, increased use of fertilisers and

pesticides might compromise both the activity and survival of certain microbes in the soil. The

first aim of this study was to test cotton-growing soils in Australia that are under different

management strategies for the abundance of microbes involved in nitrogen fixation and

denitrification. It has been achieved using the quantitative PCR technique – extracting DNA from

soils and measuring the presence of nitrogen fixation genes (nifH) and denitrification genes (nirK,

nirS and nosZ). Soils that were relatively poor or rich in nitrogen cycling genes were identified.

It has been noted that soils richer in nitrogen cyclers had also a more intense and diverse carbon

utilization patters, indicating larger microbial community with higher biodiversity. Soil N content

did not vary much under the different management strategies, but higher soil organic carbon was

associated with increased functional capacity. Possible factors influencing the nitrogen cycler

community in the tested soils that should be further investigated are the use of organic

amendments, soil enhancers and rotation with other crops as well as the intensity of nitrogen

fertilisation.

Every soil has potential to promote plant growth, with the most important players being the soil

microbial communities. Plant growth promoting microbes contribute to biofertilization, biocontrol,

and phytostimulation. Cotton seedling-disease complexes reduce crop establishment and lead to yield

loss by causing stunted growth and, in severe cases, plant mortality. The period from seed

germination to the establishment of cotton seedling is a critical stage in plant development. The

seedling at this stage, lasting up until the development of two to four leaves, is particularly

susceptible to soil-borne diseases. Improved plant nutrition and use of plant growth promoting

microbes as inoculants could sustainably increase the success of crop establishment and reduce the

impact of soil-borne diseases in cotton growing systems. The second aim of this project was to

isolate indigenous plant growth promoting microbes from Australian cotton-growing soils with the

aim of developing successful isolates into inoculants for local soils. Methods for direct and rapid

isolation of pathogen-suppressive bacteria and fungi were developed in this project and used in an

related project for further isolation of a collection of microbes, suppressing black root rot

caused by Thielaviopsis basicola and pathogens of other seedling diseases such as Rhizoctonia and

Verticillium wilts. The collection is ready for testing under field conditions. Selecting for

indigenous beneficial microbes increase the chances of survival of the re- introduced microbes in

the soil. Other plant-growth-promoting microbes of interest were those that influence water

retention and soil aggregation, secrete plant growth hormones, mediate stress response, solubilise

phosphate or suppress pathogen growth. Methods for the isolation of such beneficial microbes were

optimised for cotton-growing soils and then fine- tuned and used in a related project for producing

a collection of beneficial bacteria is ready for testing under field conditions.

In recent years soil scientists have made enormous progress toward understanding soil organisms and

their roles in ecosystems. Nonetheless, much remains to be discovered to allow the development of

practices that will promote the sustainable use of soils. Understanding what causes changes in the

belowground biodiversity and how diversity is linked to soil function, as well as how it influences

crops, would contribute to sustainable

agriculture and restoration of ecosystems.

Each year, Crop Consultants Australia - with support from CRDC - conduct a qualitative survey of cotton consultants regarding their practices and attitudes, as well as those of their cotton grower clients. The resulting report provides valuable information to the Australian cotton industry regarding on-farm practices , helping to benchmark the industry's performance in a range of key areas over time. This report, published in November 2017, looks at the 2016-17 cotton growing season.

Crop Consultants Australia Inc (CCA) is the national association

covering agronomists working in the cotton industry throughout

NSW and Queensland. CCA commenced surveying its members

and their clients in 1982 in response to a need for reliable product

usage records (quantities) and forecasts of product requirements

for the following seasons, and to provide key indicators to

chemical manufacturers of usage trends. In previous years, surveys

have been conducted of both CCA consultants and cotton

growers; however, the 2009 survey involved 23 consultants with

questions about themselves and the growers they consult for.

OverwhelmingIy, respondents were independent consultants, with

two employed by resellers. Reports from seasons 08/09 and 09/10 are included in this projects Final Reports.

Survey results for the 2008-2009 season were conducted in May and June 2009. This season was still under

drought conditions, and it should be noted that limited water

would have affected a number of management decisions.

The 2009-2010 season qualitative survey marked the second year in which the survey

was conducted with cotton consultants rather than growers. A total of

34 consultants undertook the 2010 survey - almost 50% more than in

2009 - with questions about themselves as well as their grower clients'.

An estimated total of 182,000 hectares of irrigated and dryland

cotton were grown in the 2009-10 season (source: Cotton Australia,

Australion Cotton Production Forecast March 2010 Post Flood). The 34

consultants in the 2010 survey represented about 74% of the industry

hectares and 312 growers, who represented 38% of all 2009-10

growers (source: Monsanto). The surveyed hectares comprised

approximately 86% irrigated and 14% dryland.

Peak oil demands and declining oil reserves, increased greenhouse emissions and global warming

and economic drivers for operational and cost efficiencies promote energy efficiency as one of the

most important global issues. Meeting the demands of an expanding world population is becoming

increasingly difficult not only as the global climate changes but as further limits are placed on water,

land, energy and other resources. Rising energy costs are particularly acute for agriculture, which

relies on energy intensive process to produce necessary fertilisers and chemicals. Because cotton is

a highly mechanised and high-input crop which relies on diesel, fertilisers, chemicals, water and land,

meeting the energy challenge is particularly important to Australian cotton production.

Energy efficiency is an important consideration for agriculture both in terms of rising energy costs.

Australia’s electricity prices have increased by 80% in the last 5 years, which has far exceeded the

increases in consumer price index changes in the same period. It is projected that electricity prices in

Australia will further increase by another 30% in the next 2 years. Hence, there is increased

importance in quantifying energy use, as a step toward encouraging efficient energy use on the

farm.

The CRDC has previously funded the NCEA to conduct a desktop study of on-farm energy use for a

number of case study cotton farms to understand the range, costs and contributions of energy use

to cotton production and greenhouse gas emissions. The results from this work showed that energy

use varies depending on the cropping enterprise and the farming system and that there are

significant opportunities to reduce energy and costs. While direct on-farm energy use is a small

component of the total energy used in the production of cotton lint, any savings made flow directly

to the grower. The largest energy consumption in field to factory production of finished lint is the fertilisers used in cotton production, which is the on-farm indirect energy use shown in figure 3,

below.

A more detailed study undertaken by the NCEA on a large cotton farm in the Gwydir Valley identified

significant reductions in energy resulting from the adoption of reduced tillage systems. The study

showed that the adoption of a minimum tillage system had reduced energy costs (and greenhouse

emissions) by 12% since 2000 and developing a “near zero till” system had the potential to reduce

this to 24% less than 2000 energy costs.

It is evident from this work that there is substantial scope to improve energy use efficiency in cotton

production systems, but to enable more growers to identify where they can improve, further

development of tools, processes and human capacity is required.

Energy efficiency may be one of the fastest, cheapest and easiest ways to cut farmers energy

expenditure and greenhouse gas emissions. Measuring or estimating energy use across an

enterprise is the most important first step in this process because it identifies the major energy

consuming operations across the enterprise and hence defines where the largest gains may be

made. This same process can be used to assess the net worth of any changes.

Case study of Mungindi farm managing Riparian vegetation for multiple benefits

During my two visits to the emerging cotton areas in southern NSW early January and early March, 2012, I was able to meet with all but three of the key people supplying agronomic advice to the cotton area. Two of the three, Allen Jones (Agronomic Business Solutions) and Joran Millyard (MIA Rural), I was able to have a long phone conversation with. Danielle McKay (farm agronomist with Peter Touhey Farm), I was unable to contact.

I had meetings with Heath McWhirter, Junice McCosker and John Ronan (all from Elders), Peter Hill (Yenda Prods), Brett Hay and mark Zanatta(MIA Rural), Jemma Maslem (Twynam, Gundaline) and tom Webb (agronomic business Solutions). I was able to catch up with Patrick McInnes from Hillston, who is a private consultant, whose major client is Harris Farms.

These meetings all revolved around IPM earliness, PIX management and late insects. In the case of Yenda Prods, we had a formal office meeting in the mnorning, followed by a farm inspection in the afternoon. In most cases, we met with the grower and most of his neighbours.

Elders held a shed meeting las tMonday with 25 growers turning up. Points of discussion were IPM, Boll development and late insects.

I was fortunate on both occasions to have time with Kieran O'Keefe (District Agronomist, Coleambally). Kieran is doing the Cotton Production Course at University of New England and sees cotton as an alternative crop to rice.

WEEDpak synthesizes the results of extensive research on IWM in Australian cotton farming systems from research . The WEEDpak manual includes extensive reference material to help identify weeds, an important first step in IWM. WEEDpak then discusses a number of other issues involved with IWM including herbicide resistance, herbicides and their application, farm hygiene, the control of volunteer cotton, and weed control in rotation crops. Since the main thrust of IWM is management, WEEDpak , the management of specific problem weeds

CD comprises a series of papers written for the Land & Water Australia Integration Symposium held May 2004. The symposium brought together critical thinkers from academic, policy and natural resource management sectors across Australia.