Is your tree water stressed?

How do you know if your trees are moisture stressed? In spring it can be hard to tell, but it’s a crucial time to make sure your trees DON’T dry out, particularly if they’re still flowering.

Gala apple blossom
Gala apple blossom

Why is it a problem?

In spring while the fruit is forming it goes through cell division, and if it doesn’t have enough water, there won’t be enough cells formed in your fruit.

Once that has happened, then it doesn’t matter how much water your trees get later in the season – you can’t correct this problem because the cell division phase is well and truly over, and you’ll be sentenced to a year of small fruit.

We learned this the hard way during the millenial drought. In our district here in central Victoria, traditionally there’s enough winter rainfall that there’s plenty of water in the soil in spring, and fruit trees never get water stressed at this time.

Small Anzac peaches that didn't get enough water early in the season
Small Anzac peaches that didn’t get enough water early in the season

After one particularly dry winter during the drought we had to endure a year of tiny fruit (see the peaches above – urgh!) so we quickly learned that we had to start watering the trees much earlier than usual, and it’s now one of the conditions we keep an eye on as we come out of winter each year.

With much of Australia in drought and a hot summer predicted, it’s worth noting that heat waves are another time when it’s really important to monitor your fruit trees for water stress.

Here’s an extreme example of a really dry tree:

Apple trees that haven't been watered
Apple trees that haven’t been watered

We’ve always had heat waves here in Australia, but their frequency and severity seems to be increasing. There’s not much we can do about that (apart from trying to slow down climate change), but we can make sure our trees are adequately irrigated, particularly during a heat wave, to minimise the stress on the tree.

The easiest way to check whether your trees need water is the ‘boot test’ – kick the soil under the tree with your boot and if you see dust, the tree needs watering!

Going up one step in sophistication is to dig a hole a few cm deep near the trunk of the tree with a shovel; the soil should feel cool and moist. If it looks and feels hot and dry, and is very hard to dig into, it’s too dry. (There are also many more degrees of sophistication with moisture monitoring equipment, but in most cases it’s not necessary).

The most sustainable way to protect your trees from inadequate water is to continually improve your soil quality, which in turn increases the amount of water your soil can hold. Learn how to store water in your soil here, and how to improve the health of your soil without expensive additives here.

A tree with a blocked dripper
A tree with a blocked dripper

And finally, check your irrigation system regularly! A quick 5 minute check every couple of weeks can prevent this situation, where a blocked dripper was discovered because the leaves turned yellow and started to fall!

How do you plant a green manure?

We talk about green manures and how important they are for the soil all the time, but the logistics of getting the seed into the ground can be daunting, especially on a large scale, so we decided to share how we did it this week in the nursery.

The fallow nursery block after the disc plough has been used to turned in the weeds
The fallow nursery block after the disc plough has been used to turned in the weeds

Carr’s Organic Fruit Tree Nursery is made up of three different blocks, and at any given time one of them is fallow.

This is the perfect time to plant a green manure crop to restore soil fertility,
replenish the soil, and replace the organic matter we’ve removed by growing and harvesting hundreds of fruit trees.

After hearing soil scientist Dr. Christine Jones a couple of weeks ago and learning more about the importance of multi-species groundcovers, we got inspired to ramp up our green manure seed mix even more than usual. More on that in a moment, but first, how do you actually prepare the soil?

We’re lucky enough to have equipment, so Hugh jumped on the tractor and first up used the disc plough to turn in the weeds that were already growing. You can see the result in the first photo above.

Those weeds were in effect the first green manure crop, which we’re now following up with a more diverse plant mix that will hopefully stay green over summer.

We’re always wary about using equipment like discs, harrows or rotary hoes because of the way they smash up the soil and can damage microbes, particularly soil fungi.

But you’ve also got to find a way of getting the seed into the soil, and Dr. Jones was very much of the opinion that it’s worth disrupting the soil (albeit as minimally and infrequently as possible) to get diverse, perennial groundcover crops established. The benefit should quickly outweigh the initial cost.

The disc did a good job of turning most of the weeds in, but it was still too rough for the seeds to connect with the soil well enough, so next we put on the rotary hoe.

Hugh using the rotary hoe to prepare the soil for the green manure seed
Hugh using the rotary hoe to prepare the soil for the green manure seed

You can see the difference just one pass with the rotary hoe makes (on the left hand side of the photo above). It’s still not a super smooth seed bed, but it’s good enough for the seeds to hit the soil when they’re broadcast, rather than getting stuck on a clump of grass – where they definitely wouldn’t germinate and grow!

If we had seed-drilling equipment that could inject the seed straight into the soil we wouldn’t need to do this step, and in fact many innovative regenerative farmers are sowing seeds directly into pasture these days, with no soil disturbance of loss of ground cover at all, and getting excellent results.

The green manure seed mix spread on the soil
The green manure seed mix spread on the soil

But needs must, so the next step is broadcasting the seed by hand. It’s always a challenge to scatter the seed evenly over a patch this size, but by dividing the patch into sections and weighing out portions of the seed mix we got a pretty even spread.

The last step is raking the whole patch to get a light cover of soil over the seeds, and finally give the whole patch a really good watering in.

Raking the seeds to get a light cover of soil over them
Raking the seeds to get a light cover of soil over them

We’ve always used a fairly diverse mix of seeds for the green manure, but this year we went nuts! We were also influenced by Dr. Jones to make a couple of other modifications – we mixed in a good dose of worm castings out of our worm farm, and then we soaked the seeds in raw whey (sourced of course from Sellar Farmhouse Creamery) for a couple of hours before we sowed. These are both great sources of microbial innoculation to help the seeds get the best possible germination rate, and because we had access to both we gave it a double whammy!

The green manure seed mix, mixed with worm castings and soaked in whey
The green manure seed mix, mixed with worm castings and soaked in whey

This left the seed mix pretty wet, so then we mixed it with enough dry sand to make it spreadable.

The reason we were inspired to increase the diversity of our green manure seed mix was that Dr Jones explained that prior to European invasion, “the natural grasslands that once covered vast tracts of the Australian, North American, South American and sub-Saharan African continents – plus the ‘meadows’ of Europe – contained several hundred different kinds of grasses and forbs.”

Several hundred species! Imagine that!

A multi-species crop is an entire community of plants working together to convert sunlight into liquid carbon (remember learning about photosynthesis at school?) which it feeds the microbes in the soil. It’s called the plant-microbe bridge, and it builds soil, converts carbon from the air into stable compounds in the soil and holds far more water in the soil.

So, feeling inspired, we set out to create our own multi-species crop. We didn’t quite get to 100 species, but we managed 40:

  • Alfalfa (lucerne)
  • Amaranth
  • Basil
  • Beetroot
  • Broad bean
  • Buckwheat
  • Butterfly pea
  • Chia
  • Cocksfoot
  • Coriander
  • Corn
  • Dill
  • Endive
  • Fenugreek
  • Kidney beans
  • Lab lab bean
  • Linseed
  • Medic
  • Millet – French white
  • Mung bean
  • Mustard
  • Purslane
  • Quinoa
  • Radish
  • Rocket
  • Sesame
  • Soy bean
  • Sunflower
  • Turnip
  • Vetch

Now we just have to get them to grow! Stay tuned for photos….and if you’d like to find out more about how to quickly build fertile soil at your place using green manures, we’ve packed a lot more detail into this short course.

Capeweed – love it or hate it?

Capeweed - pretty yellow flowers, but is it a desirable plant?
Capeweed – pretty yellow flowers, but is it a desirable plant?

We’re often asked what we think of capeweed, which is often seen growing in great abundance all over the countryside (and our farm) in spring.

If you’ve been following us for a while, you’ll know we’re generally big fans of weeds (we even wrote a short course about it called Learn to Love Your Weeds,) but does the same apply to a huge monoculture of one weed?

A yellow carpet of capeweed in the orchard
A yellow carpet of capeweed in the orchard

Capeweed germinates in autumn and winter, so is most evident in spring, dying off in summer – and that creates a problem right there, because where you have an over-abundance of capeweed, you end up with bare ground in summer – which is a terrible thing for the soil.

It’s basically a weed of cultivation, pastures, lawns and disturbed areas. Stock will eat it but don’t like it (and the woolly seeds can cause impaction), it can taint milk and where it’s the dominant feed, nitrate poisoning of stock is possible.

Sounds terrible doesn’t it?

A bee gathering pollen from capeweed flowers
A bee gathering pollen from capeweed flowers

But the problem is not the capeweed itself. It can actually play a useful role in covering bare soil and keeping it cool, attracting bees, and – when part of a rich biodiversity of plants – filling a niche in the ecosystem.

The problem is the soil – and even more importantly, the practices that have led to soil and diversity imbalances that result in this kind of destructive monoculture.

A carpet of capeweed is a stark visual reminder that whatever we’ve been doing to the soil is all wrong! It’s an indicator of acid soil, compaction and can be an indicator of waterlogging or salinity.

It’s telling us to sit up, take notice and change our practices immediately.

We need to get more organic matter into the soil, rebuild a wide diversity of plants, and particularly focus on including plants that will stay green throughout summer.

The work of eminent Australian soil scientist Dr Christine Jones (www.amazingcarbon.com) tells us that bare soil should be avoided at all costs as it heats up to at least 60C in summer, which causes it to rapidly lose moisture, kill soil microbes, and contribute to climate change!

So, that’s the long answer!

The short answer is that while a mooculture of capeweed (or any plant) has its drawbacks, it’s a fantastic indicator plant, a good bee attractor, and can be a very useful member of a healthy biodiverse garden or pasture.