Beginning a Walnut Production project is like starting a marathon of endless decision-making:
Location, land, soil, water, crop, variety, rootstock, irrigation method, team... Answers to each of these questions determine the potential of your plantation throughout its life cycle. Impact of these initial decisions are generally very difficult and costly, if not impossible to change later on. These are the big decisions that you really need to make very carefully, and you cannot afford to outsource making them. You can hire the best technical advisor, but chances are, he or she will not be around in 10 years time, when your orchard is just becoming a young producing orchard and you are realising the effects of these initial decisions. So get as much advice you can, from people who have positive proven track records, as well as from people who have failed. But in the end, make sure to reach to a level of understanding that you can not only make your own decisions, but also own those decisions in every detail, as you will need to live with their consequences for as long as your orchard continues to exist.
There is a popular saying among sailors that I like to repeat: "Every new sailor begins with luck, but only smart ones gain experience before their luck run out." I have seen many failed walnut projects, because their owners/managers did not push themselves to gain experience and knowledge, continuing their operations entirely relying others´ recommendations.
Land, location, soil:
I can almost say that there is no perfect orchard. Even the orchards that would get the highest marks in most parameters have challenges, "achilles tendons" you may call them. Choosing the "right" land, is navigating through several parameters, making a choice in which to compromise, and to what extend, while taking measures to manage these compromises.
To give a general idea, among the key "agronomical" parameters you can list, soil fertility, water infiltration, manageability of the terrain, physical and chemical characteristics of the soil. These are soil-related technical parameters that should also be considered along with others, such as micro climate, chilling hours, land availability, price, safety, availability of electricity, labor and perhaps the most important of all of these parameters WATER.
And finally, you can have non-technical parameters, like proximity of the orchard to your residence, having a nice scenery, or anticipating a price increase of land in a specific area. All of these parameters may impact your decisions, but if the real intention is to establish successful orchard, obviously your "hierarchy of decision making" should prioritise the strategic needs, such as water availability, soil characteristics and climate. Most other parameters can be modified in time, with additional costs and consistent effort.
Water - Water - Water:
Among all of these, water availability is so critical, that it deserves to be separated from all the rest. In fact, looking for a walnut property is very much looking for long term security of abundance of water source. Do not listen to people who may tell you that:
"a particular land has enough water",
"and that walnut plants in fact do not need much water",
"or even if they do, this is just for the first few years".
Such remarks made without real experience are usually unreliable, biased if not derived from other commercial motivations. Instead, make sure to get the facts from reliable resources.
Start by making an effort in learning the importance of water, and trying to build a realistic and conservative long term water budget that should be your guidance in planning and diversifying your water sources. Understand the strengths and weaknesses of each of these water resource types, taking into account their quality as well as their quantity.
Let us just begin by emphasising that "a commercial level productive walnut orchard" needs, throughout its commercial life span lots of water, which will increase every year, until reaching a maximum value. At this point, it is important to put an objective value to this "lots of" quantity. Your water budget, should identify, at least initially, the flow rates of your resources, wells, irrigation networks, lakes and your water reservoirs, etc. You must take into account the replenishment of these resources. On top of this, try to build a model of amount of water that you will need during different years of your plantation. You will need to notice that the amount of water needed will increase every year, reaching to a maximum level as your orchard canopy (leaf coverage area when viewed from above) reaches its maximum level as water loss in your orchard occurs by evaporation as well as by perspiration from leaves (similar to sweating by animals, in order to cool themselves).
Always base orchard water need on plantation area and canopy, rather than number of plants. You should create a mathematical model of the amount of water your operation can be supplied with (in +) and the amount of water you will use (in -). Of course, taking one step forward, you can also take into account the amount of rain that will be received on the orchard during the irrigation period. However, be very careful as mm of rain received should be considered using a "discount" factor, as some of the rain water, especially in short intensive ones", will be discharge from the soil, in surface runoff, rather than being absorbed by the soil.
Here is a simple example for a water budget model, which you should build based on your orchards realities.
I think the safe way of establishing this water budget is to begin figuring out the amount of water need when your trees are full grown. In doing so, you should learn
The mechanism of water running inside the plant,
How/why water is being used by the plants,
How water is lost from the orchard,
The concepts of Evapotranspiration, Crop Coefficient,
Plant moisture stress (PMS), and the effect of Relative Humidity on it,
Midday leaf water potential.
A safe, rule of thumb number will be between 6,000 - 8,000 m3 of water per every Ha of plantation per year (when plants reach their full maturity). This is (based on an average of 7,000m3): 7,000 / 10,000 = 0.7 m or about 700 mm of water per m2 of plantation area per year. The amount of water you need in years prior to reaching full maturity depends mostly on the leaf coverage area.
You can have a basic model of:
Year m3/Ha
1 1,500
2 2,000
3 3,250
4 4,000
5 5,000
6 6,000
7 7,000 - 8,000
This is just an oversimplified presentation of the water need per Ha of plantation in years. Do not fall into the mistake of using these figures, your actual figures will be different. But come up with an accurate calculation based on your climate, soil characteristics and the canopy of your orchards in every year.
Availability of the amount of water that you will need when you reach your cruise production levels (8-10th year), is probably the single most important factor that you must take into account before making a final decision on your orchard. Do not rely on what others think and tell you on the availability of water and its sufficiency for Walnut. This information is publicly available. Depending on climate, the safe quantity to secure in the long term is about 7,000 - 8,000 m3/Ha of plantation per year. Learn about the basic concepts of how plants and orchards loose water, in what amounts and when, and plan according to that. Evapotranspiration, capillary action, etc. There is a fantastic book on this subject giving you clear descriptions on these concepts but also has chapters that focus on water needs for many crops, including Walnuts.
Crop yield response to water
When evaluating your potential land, in general, you should be looking for good fertility. Among many other parameters, high organic matter is an important indicator for this. A chemically balanced soil without excess salt or boron must be your preference.
Good fertigily is often, but not always, associated with soils with higher clay percentage. Clay, the smallest of the three physical particles that makes of the soil is often the cause of a major problem: Poor drainage.
Of many different characteristics that are popular among land-searchers, two very important ones are often missed:
Walnut plants do not tolerate well excess water in their root zones. By using certain (mostly clonal or hybrid) rootstocks you can manage this situation to a certain extend, but in general soils with good infiltration rate should be a clear choice. The shape of the orchard surface is also important in discharging accummulated water after heavy rains. Having deeper areas surrounded by higher surfaces causes water accumulation. Make an effort in soil preparation in flattenting these surfaces so the excess of water will be discharged from your plantation areas with gravity. There will be other areas where drainage ditches should be designed and built. Making a 3D topographic map of your land is a valuable investment that you will not regret in identifying areas that requires drainage work. Having small but manageable slopes in your land, especially in a single direction will help manage and avoid excess water accumulation.
It may sound contradictory to my last sentence, but you should avoid significant elevation changes in your potential plantation area. As too flat plots have challenges, so do too steep ones. Throughout the project, you will be walking hundreds, if not thousands of times in every cm of the land. Whether on foot or with machinery, any type of excess slope will make the land more difficult to manage, harvest, increase your cost, and even make it more difficult to identify problems. In addition to challanges in mobility, excess elevation changes will make it a lot more difficult to manage stabilizing the pressure in your irrigation lines resulting in irrigation problems.
As flat as you can, but with mild slopes, enough to prevent water accumulation will be a good balance in terrain choice.
Oct. 2, 2022
Lisbon
Next: Ep. 3 - The expectant grower
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