Erosion control, irrigation and fertiliser management and blueberry production: Expert interviews. Geoff Kaine and Jeremy Giddings

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1 Erosion control, irrigation and fertiliser management and blueberry production: Expert interviews Geoff Kaine and Jeremy Giddings

2 Author Dr Geoff Kaine Geoff Kaine Research Hauturu, Waikato, New Zealand Jeremy Giddings NSW Department of Primary Industries Dareton, NSW 2717 vember 2016 Acknowledgements We would like to thank Pia Dollmann of Coffs Harbour Regional Landcare for her support and assistance. Disclaimer: The author has prepared this report for the sole use of the clients and for the intended purposes stated between both parties. Others may not rely upon this report without the written agreement of the author and the clients. part of this report may be copied or duplicated without the express permission of the author or the clients. The author has exercised due and customary care in conducting this research. other warranty, express or implied is made in relation to the conduct of the authors or the content of this report. Therefore the author does not assume any liability for any loss resulting from errors, omissions or misrepresentations made by others. Any recommendations or opinions or findings stated in this report are based on the circumstances and facts at the time the research was conducted. Any changes in the circumstances and facts on which the report is based may affect the findings and recommendations presented. 2

3 Erosion control, irrigation and fertiliser management and blueberry production: Expert interview results Introduction There is concern over the potential for sediment and nutrients from blueberry farms to contaminate streams, lakes and marine environments in northern New South Wales. The extent to which nutrients and sediments are discharged from blueberry farms depends on the practices growers employ to manage irrigation and fertiliser, and to limit erosion. In this paper we describe the irrigation, fertiliser and erosion control practices growers employ, and the factors governing their choices in regard to these practices. The descriptions are based on an analysis of interviews with ten industry experts. The results of the analysis will be verified by interviewing a representative sample of blueberry growers. The theoretical framework underpining the study is described in Kaine and Johnson (2004). Blueberry production systems Blueberries are a relatively new high-value crop in the Coffs Harbour region. Most blueberry production is field-grown but an increasing proportion is grown hydroponically. Field blueberries are grown across a variety of soil types and topographies on the rth Coast ranging from flat country with sandy, well-draining soils through to extremely steep country with poorly draining, dispersive clay soils. The varieties grown on the rth Coast are shallow-rooted and are particularly sensitive to both under- and over-watering. To reduce the chance of waterlogging plants are grown in raised mounds or rows up to 90 metres in length. Rows are aligned with, rather than across, a slope to reduce the risk of accidents with machinery and to maximise efficiency in machinery operations. The rows are covered in weed mats or mulch to reduce weed infestation. In addition, to further reduce the risk of weed infestation, a narrow margin bordering the mats may be kept clear of vegetation by spraying with herbicides. Blueberries are also grown hydroponically in substrates contained in pots, usually under cover, or in bags in the field. Production under cover in Spanish tunnels provides greater control over watering and nutrient application, and the higher temperatures in tunnels promote plant growth and early production. Production under cover also provides greater flexibility in harvesting. However, 3

4 pest and disease pressure is greater when production is under cover because of the higher temperatures and humidity. Labour associated with pruning, picking and pest control constitute between 70 and 90 per cent of production cost. This means growers will change production systems and growing practices primarily for two reasons: to reduce labour costs and to increase yields. Growers are unlikely to change systems or practices to reduce costs other than labour because the resulting savings would have only a trivial impact on profitability. Erosion control and blueberries Field production The aligning of the rows along, rather than across, a slope creates situations where rainfall runoff is channeled between the rows. When rain is intense the channeling of runoff can result in rapid erosion, creating gullies in between or bordering the rows leading to the deposition of sediment in farm dams and nearby streams. In extreme cases rows may be damaged and plants washed away. The gullies are a hazard for machinery and a safety risk for labour. Erosion of this nature is most likely on steep slopes and sandy soils. The risk of erosion may be reduced by planting a cover crop between the rows, or by placing mulch or reflective weed mats between the rows, and by installing stop banks and shorter rows. Hydroponic production There is very little risk of erosion with hydroponic systems. Conclusion While repairing damage from erosion may be expensive these costs are likely to be only a relatively small component of total production costs. Consequently, there will be little motivation to make substantial investments to prevent erosion, unless it results in considerable production losses. This means growers are unlikely to be responsive to efforts to promote the adoption of technologies and practices to prevent erosion unless such technologies and practices can be linked to increased production (reflective weed mats, converting to hydroponic production, shifting to flat country) or avoiding higher labour costs (possibly in the form of occupational health and safety claims or the introduction of more stringent health and safety regulations). These results are summarised in Figure 1 where the population of blueberry growers is classified into four segments. To begin with the population is divided into those who have field-based production systems and those that have substrate-based production systems. The risk of soil erosion in regard to the latter is low. 4

5 Field based growers are then divided into those that have sloping country and those that do not. Those that are on sloping country are classified as being at risk of erosion because of their topography. Growers on flat country are sub-divided into those that have sandy soils and those that do not. The former are classified as at risk of erosion because of their soils while the latter are classified as low risk. The end result is a classification of blueberry growers by the degree of erosion risk given their production context. Segments one and two consist of growers with systems that are at relatively high risk of experiencing erosion. The growers in these segments could be the targets of an extension program promoting technologies and methods to prevent erosion. The success of such a program will depend the extent to which a link can be established between these technologies and methods, and improving yields. Irrigation and fertiliser management in blueberries Field production Blueberries are watered using drip irrigation, typically with drip lines laid either side of the plants under weed mating. Two lines are required to obtain an even wetting of the mound, which ensures plants are balanced in their growth. Two lines also enable water to be applied more quickly and provide an element of redundancy should a dripper fail. On steep slopes water pressure varies in drip lines resulting in the uneven application of water along rows. Plants at the top of the row may receive too little water while plants at the bottom of the row may receive too much resulting in lower yields in both instances. The installation of pressure compensating drippers and drainage plugs at regular intervals along lines can improve the consistency of water pressure, within limits. Installing laterals and converting to shorter drip lines can also achieve more uniform pressures. Originally, blueberries were irrigated once or twice a week for up to three hours at a time. This schedule had an unfavourable affect on yields as the berries suffered from too little water between irrigations and too much water during irrigations. The waterlogging of plants meant that at irrigation water, and accompanying nutrients, passed rapidly through the root zone. Irrigation scheduling has changed over the past few years. Typically, plants in rows are now watered most days each week for between ten to thirty minutes. This schedule varies depending on the season and stage of plant growth with irrigations occurring less frequently in winter and more frequently in summer. The variety of blueberry and soil type will also affect the frequency and length of irrigations. Fertiliser is applied to the plants a couple of times a week over winter and most days in summer. 5

6 Yes Are blueberries grown in field rows? Yes Are blueberries grown on a slope? SEGMENT ONE High risk (slope) Yes Are blueberries growing on sandy soil? SEGMENT FOUR Little risk of erosion (substrate) SEGMENT TWO High risk (soil) SEGMENT THREE Low risk of erosion (flat) Figure One: Context diagram for erosion risk 6

7 The shift to more frequent irrigations with shorter run-times means there is less likelihood that plants are being under or over-watered. This shift has resulted in an increase in yields while reducing the volume of water applied by around 30 per cent. This means growers are less likely to run short of water in a drought, or are able to expand production. The shift to more frequent, shorter irrigations has probably substantially reduced the extent to which irrigation water, and accompanying nutrients, moves beyond the root zone. Most growers rely on harvesting rainfall runoff for irrigation water. In particularly dry seasons some growers have almost exhausted their irrigation supplies. Growers can employ a variety of tactics in these circumstances including drying-off one or more rows, limiting the irrigation of harvested rows, and reducing the irrigation of varieties that are more tolerant of dry conditions. Few growers rely on soil moisture monitoring equipment to schedule their irrigations. In the absence of substantial cost savings from reducing water use or severe restrictions on water supplies, previous studies (Kaine and Bewsell 2005; Hill et al. 2012) suggest that growers are only likely to employ monitoring equipment to assist them in either establishing a schedule in a new plantation or to diagnose the cause of a production problem in an established plantation. The uneven distribution of water along rows on steep slopes also limits the value of soil moisture monitoring. The same may also be said in regard to nutrient testing. Hydroponic production Pulse irrigation is applied to blueberries grown in substrate. The porosity of the substrate means the penetration of water through the substrate is quite uniform and predictable. This means wetting of the substrate can be tightly controlled enabling the precise application of water to the plant. Consequently, frequent, short irrigations are practical. Plants in substrate may be irrigated three or four times a day for two or three minutes at a time. Fertiliser is applied each irrigation except when substrates require periodic flushing to remove salts. Conclusion Given irrigation and fertiliser constitute a small fraction of the total costs of blueberry production, cost savings will not motivate growers to adopt water saving practices. However, there is substantial evidence that yields are quite sensitive to over or under-watering. Consequently, growers are likely to be responsive to efforts to promote the adoption of improved irrigation practices on the basis that those practices will increase yields. These results are summarised in Figure 2 where the population of growers is classified into four segments. To begin with the population is divided into those who have field-based production systems and those that have substrate-based production systems. The risk of water and nutrient discharge below the root zone in regard to the latter is low. Field based growers are then divided into those that have sloping country and those that do not. Those that are on sloping country are classified as being at high risk of discharging water and nutrient into the environment primarily 7

8 because of the uneven application of water along rows on steep slopes. These growers may be responsive to the promotion of practices that improve yields by providing better uniformity of water application and reducing the likelihood of under or over-watering plants. These practices include installing pressure compensating drippers and drain plugs, and converting to smaller rows. These growers are unlikely to adopt soil moisture monitoring equipment to assist in scheduling irrigations as they have limited control over the uniformity of water application within rows. Growers on flat country are sub-divided into those that have sandy soils and those that do not. Both are classified as at some risk of discharging water and nutrients into the environment. These growers may be responsive to the promotion of irrigation scheduling practices that improve yields by better matching water applications to plant requirements. These practices include using soil moisture monitoring equipment to assist in determining the water and nutrition requirements of plant at different stages and through the season, and scheduling irrigation and fertigation accordingly. Growers on sandy soils would probably need to schedule more frequent irrigations than growers on heavier soils. The end result is a classification of blueberry growers by the degree of water and nutrient discharge risk given their production context. Segments one, two and three consists of growers with systems that are at risk some risk of discharging water and nutrients into the environment. The growers in segments could be the targets of an extension program promoting irrigation technologies and practices to reduce the risk of discharge because these will improve yields. Conclusion Using information from interviews with ten industry experts we have identified the set of factors that are thought to influence the risk of water and nutrient discharge, and the risk of erosion, from blueberry farms. Given that blueberries are a high value crop and irrigation and fertiliser constitute a small fraction of the costs of production, we propose growers will be strongly motivated to adopt erosion control, irrigation and fertigation technologies and practices that improve yields. Conversely we propose growers will only be weakly motivated, if at all, to adopt erosion control, irrigation and fertigation technologies and practices that may reduce erosion control, irrigation and fertigation costs but do not improve yields. The set of factors we identified that are thought to influence the risk of water and nutrient discharge, and the risk of erosion, from blueberry farms will be validated by interviewing a sample of blueberry growers. These interviews will also allow us to test our proposals in regard to the motivation of growers to adopt erosion control, irrigation and fertigation technologies and practices. 8

9 Yes Are blueberries grown in field rows? Yes Are blueberries grown on a slope? SEGMENT ONE High risk of discharge (slope) Yes Are blueberries growing on sandy soil? SEGMENT FOUR Little risk of discharge (substrate) SEGMENT TWO Some risk of discharge (sandy soil) SEGMENT THREE Some risk of discharge (heavy soil) Figure Two: Context diagram for water and nutrient discharge risk

10 References Hill M, Rowbottom B and Kaine G (2012) The use of soil and petiole nutrient testing by Australian wine grape growers, Extension Farming Systems Journal, 8 (1): 1-9 Kaine G and Bewsell D (2005) Adoption of Integrated Fruit Production: A Quantitative Study, Client Report to the Victorian Department of Primary Industries, AgResearch, Hamilton, New Zealand Kaine G and Johnson F (2004) Applying Marketing Principles to Policy Design and Implementation, Social Research Working Paper 02/04, AgResearch, Hamilton, New Zealand 10