Water, water, water!

Thornleigh is being geared up to grow lots and lots of yummy things: Mangoes, pumpkins, tomatoes, avocados, rock-melons and so forth. All these yummy things will give Lord Howe Island visitors and residents the energy they need to perform strenuous island activities. For example, swimming with turtles at Old Settlement Beach. But where do all those vegetables, fruits, and other plants get all that energy from?

A turtle saying hello at Old Settlement beach
A turtle saying hello at Old Settlement beach

Photosynthesis, of course! Plants fuel their activities by converting light energy from the sun into chemical energy in the form of carbohydrates. Photosynthesis requires carbon dioxide, water, and photons. Cleverly, we have worked out that we can get photons by sticking Thornleigh’s crops out in the sun. Around about one sextillion (that’s 10^21!) photons per second hit every square metre of Thornleigh’s garden beds during the day. We’ve got photons, then!

Photosynthesised yumminess
Photosynthesised yumminess

How about carbon dioxide? A little back-of-the napkin maths reassures us that there are approximately 3.9 tonnes of carbon dioxide swirling around Thornleigh’s fields at any moment. If we do get worried that there isn’t enough carbon dioxide in Earth’s atmosphere, we could always leave Matilda idling in the paddock. We’ve now managed to acquire two out of three components necessary for photosynthesis. And we didn’t even have to do anything! This farming thing isn’t all that hard, so far. But of course, the third component is the tricky one.

Sweet potatoes sucking in carbon dioxide
Sweet potatoes sucking in carbon dioxide

There are two wells on Thornleigh, both of which may be used to access Lord Howe Island’s groundwater reserves. They are very old, the first being established by Phillip John English Dignam in the 1890’s. In the early 20th century his son, a young Phillip William Dignam, hauled water from the wells to the fields in a wheelbarrow. Later, Phillip W. employed flood irrigation techniques: Filling the trenches between planted rows with water.

Phil working in the Thornleigh gardens, mid 20th century
Phil working in the Thornleigh gardens, mid 20th century

Somewhat surprisingly, Robert and Lindy have not been able to convince their sons to spend all day carting water to the fields in wheelbarrows. Flooding is also much less efficient than modern irrigation methods, such as drip irrigation. The combination of drip lines, pipes, and pumps could supply Thornleigh’s fields with water, completing the trifecta of components we need for photosynthesis. But is using groundwater for general irrigation a good idea?

Irrigate me!
Irrigate me!

Groundwater is not an infinite resource: It varies in quantity and quality.  The amount of groundwater available depends on the volume of rainfall in local catchment areas. Lord Howe Island receives plenty of rain: The yearly average at the centre of the island is 1499mm, compared to 1212mm in Sydney’s CBD and 662mm in Melbourne’s botanical gardens. Slightly less rain falls in the northern settled areas than the south, where mounts Lidgebird and Gower induce orographic precipitaion. Look closely at the graphs below and you’ll notice another important characteristic: Rainfall drops significantly in the summer months.

Thornleigh
Map showing rainfall at different Lord Howe Island BOM monitoring stations

The drier summer months coincide with the peak season of Lord Howe Island’s most important industry: Tourism. During the tourist season, the population of the island doubles. Suddenly, there are 400 more people flushing toilets, taking showers, and washing clothes. Almost every residence and business on the island uses rainwater tanks, but in summer groundwater is an essential component of the water supply, especially for the big guest houses.

To keep the lagoon looking this beautiful, Lord Howe Island needs to manage water supplies carefully
To keep the lagoon looking this beautiful, Lord Howe Island needs to manage water supplies carefully

Back in 1996, groundwater studies revealed that during the summer months, groundwater extraction and septic waste disposal were causing elevated salinity and nutrient levels in Lord Howe Island groundwater. This poses potential risks to human health and, via runoff, the health of the islan’ds marine environment. Thornleigh is right in the middle of one of the zones identified as showing signs of strain. Evidently, a restored heritage farm pumping thousands of litres of water out of the ground in summer is not what Lord Howe Island’s water supply needs! But we need to photosynthesise in summer, so what to do?

nitrateamp

At first, the answer seems simple. Water tanks! By storing bucket-loads of rain water in the winter, Thornleigh’s drip irrigation systems could hum away through the summer without putting any additional strain on the island’s groundwater supplies. Polyurethane tanks of all shapes and sizes can be had for reasonable prices. To store rainwater, we could order a whole bunch of these tanks, attach them to shed roofs across the property, and complete the photosynthesis equation.

Brenden re-positioning a polyurethane rainwater tank
Brenden re-positioning a polyurethane rainwater tank

There is a hitch though: Putting a water tank on Lord Howe Island is not like putting a water tank on the mainland. It’s not possible to order a tank and have it delivered on the back of a truck. Everything bigger than a human that comes to the island needs to come via ship, and that is an expensive exercise.

The Island Trader visits Lord Howe every few weeks, carrying essential cargo
The Island Trader visits Lord Howe every few weeks, carrying essential cargo

Polyutherane tanks are monolithic, and take up just as much space in a cargo hold as they do when installed. We will need well over one hundred thousands litres of water to reliably get through summer. Shipping that much plastic is just not feasible! Fortunately, there’s another option: The Stockman tank from Tankworks.

920kgs of environmentally responsible farming!
920kgs of environmentally responsible farming!

Stockman tanks are low profile, high volume, sturdy water tanks that come flat-packed in kit form. Instead of filling a ship’s cargo hold with plastic tanks full of air, the Stockman can be transported efficiently in a crate.

Robert Jeremy (left) and Rob "Bert" Simpson during tank 1's construction
Robert Jeremy (left) and Rob “Bert” Simpson during tank 1’s construction

The tanks selected for Thornleigh are 1.9 metres tall, 7.2m in diameter, and have a capacity of 77,000 litres. They are made of corrugated galvanised steel, and feature a polypropylene based woven fabric bladder.

Brenden enduring searing summer heat to install the bladder inside tank 1
Brenden enduring searing summer heat to install the bladder inside tank 1

Both tanks are now completed, in time for the 2015 winter rains. Their combined 154,000 litre capacity will ensure that Thornleigh’s drip irrigation systems can continue to feed water to the gardens through the summer months.

Brenden (Left) and Robert working on tank 2 under the supervision of Bill Retmock
Brenden (Left) and Robert working on tank 2 under the supervision of Bill Retmock

For more information about the Stockman tanks, head over to the Tankworks website. If you would like to hear more news from Thornleigh, sign up for the Thornleigh newsletter. See more photos of the tanks under construction in an extended album, right here on the Thornleigh website.

 

 

Newsletter April 2014

We live in a world that has practised violence for generations – violence to other creatures, violence to the planet, violence to ourselves. Yet in our garden, where we have nurtured a healthy soil-plant community, we see a model of a highly successful, non-violent system where we participate in gentle biological diplomacy rather than war. The garden has more to teach us than just how to grow food.

– Eliot Coleman
Four Seasons Harvest

Starting an Organic Market Garden

The big news since the Friends of Thornleigh visited the property in January has been Robert and Brenden’s three day intensive Milkwood Permaculture course on ‘How to Start an Organic Market Garden’. The course ran for 3 days at Milkwood Farm near Mudgee and covered every aspect of small farm organic market gardening – from developing the business and marketing plan to site preparation and organic growing techniques.

Brenden at Milkwood studying the art of incinerating bones and wood for phosphorus and calcium
Brenden at Milkwood studying the art of incinerating bones and wood for phosphorus and calcium

The teacher, Michael Hewins, is involved in a small 2.5 acre farm in Dural called ‘Common 2 Us’. Between what we saw and learned at Milkwood and heard about Common to Us, we are convinced that Thornleigh has a bright and productive future ahead and will make a real contribution to the Island’s sustainability.

Brenden outside the woolshed classroom during a break.
Brenden outside the woolshed classroom during a break.

Assessing our Site

One of the very first steps for building an organic market garden is assessing the site. We are fortunate that Thornleigh has its farming heritage to fall back on and the foundations are already there. The property is just the right size for a small market garden. The site aspect and topography are just right and the surrounding trees and forest (some natural, some man-made) provide excellent protection from wind and harsh weather. This, together with the Island’s temperate climate, creates an excellent micro-climate for growing produce.

We have continued work repairing garden infrastructure with fencing restored on the northern boundary (between the nursery and Hazel Payten’s place), and a gate installed on the boundary with the nursery. A large number of bags containing used peat moss, which had found their way onto the property from the former nursery operation, were returned to the nursery site. A second gate has been added to the fence on the southern boundary adjoining TC Douglass Drive.

The soil at Thornleigh is obviously good stuff, but we need to take a look inside to find out whether it’s ready for vegetables after lying fallow for so long.

Soil samples have been forwarded to SWEP Laboratories in Melbourne for analysis to determine their nutrient and PH levels (acidity/alkalinity). Water samples from the two wells will be forwarded shortly to determine its suitability and how we might need to treat it for irrigation.

A big challenge for us will be finding resources on the Island to provide nutrients to the soil. Organic market gardens on the mainland have access to all the nutrients and minerals they need but shipping large quantities to the Island will be prohibitive. Here’s an example of lateral thinking learned from Milkwood:

Plants need phosphorus for cell division and development of new tissue. Phosphorus is also associated with complex energy transformations in the plant. Adding phosphorus to soil low in available phosphorus promotes root growth and winter hardiness, and often hastens maturity. An organic gardener on the mainland would solve phosphate deficiency by adding phosphate rock from the local farm store. At Thornleigh we can avoid shipping costs and act sustainably by burning and crushing animal bones to source phosphate (and calcium). In fact, this is just the bone in good old ‘Blood and Bone’ fertiliser.

What’s Growing

The passionfruit which Brenden planted in January have started to flourish with the recent rains. And the old banana grove in the first garden is making a strong comeback.

Some of the old avocado trees threw off a large crop recently. We think these trees might be the heritage ‘Duke’ variety from California which has been described as the ‘heirloom of heirloom avocados’. The variety was popular in the early 1900’s but it didn’t transport well because of its thin skin. Many of the modern varieties such as Haas are now grafted onto Duke rootstock because of Duke’s resistance to Phytophthora root rot. If we are right about this, the avocados at Thornleigh will be one of only a few known remaining gardens in the world with this variety of avocado.

Over winter we will be planting a cool season green manure in the first garden. Green manures help to restore bulk organic matter and fix nitrogen from the atmosphere back into the soil. The green manure will be slashed and ploughed back into the soil before preparing beds for vegetables. In summer we will plant a warm season green manure on the second garden and in parts of the paddock to improve nutrition and suppress the kikuyu.

We are pleased that the Board has given approval for the importation of a large number of citrus trees which we will start planting over the next 12 months.

Our Heritage

A lovely photo of Thornleigh has been located in a photo album recently donated to the Island Museum. The album was assembled by Harold Rabone, an early Island historian, as a gift presentation for State Governor, Sir Dudley Rawson De Chair, who visited Lord Howe aboard HMAS Melbourne in September 1927. The album contains a commentary on Island life and history plus many superb photos of the Island. (Harold Rabone was a gifted photographer, as well as being a capable writer.) The photos are mostly scenic, but some show activities like unloading the ‘Makambo’, fishing parties, island picnics and Islanders’ homes – including the original home at Thornleigh.

Thornleigh in September 1927
Thornleigh in September 1927

During his most recent visit Robert unearthed an old newspaper article from The Town and Country Journal (March 1908) which included the following description of Thornleigh:

“…islanders, even when they give scarcely any attention to the matter, easily keep their clearings well stocked with maize, lemons, peaches, passionfruit, apples, tomatoes, Cape gooseberries, cucumbers, melons, guavas, pomegranates, chokoes, grapes, beetroot, cabbage, pumpkins and other types of vegetables. But in some cases, notably in that of Mr Phil Dignam – a former resident of Goulburn, N.S.W. – extra care and skill have resulted in the formation of gardens that are indeed pleasant to see. Huge quadrangles have been chopped out of the dense dark-green forest, and the deep chocolate soil artistically laid out in a succession of neat square beds, that are fenced off from each other by straight-clipped hedges of oleander, 10 ft high and 30 in thick, which shield the gardens from high winds.”

This description has been added to the history of the property currently being written. It is Robert, Lindy and Brenden’s greatest hope that they will be able to recreate this amazing ‘picture’ of the property so that residents and visitors can again enjoy Thornleigh’s agricultural bounty.

Our Next Issue

In the next issue we will talk about our plans for water infrastructure, the meaning of results of the soil and water testing, how we are going to manage fruit fly so we can bring the old fruit trees on the property back to production, and more about David Jeremy’s cataloguing of the hundreds of old photos found at Thornleigh.