I’m working in Chinandega, Nicaragua with some local farmers. We’re hoping to grow tomatoes, and I was wondering if anyone has good resources on growing organic tomatoes. Here are some of the questions I have:
What’s the best spacing for trellised tomatoes? We’re planning on pruning to one lead.
General fertilizer recommendations? Tomatoes are heavy feeders, and we’re working on doing some soil tests, but I’d love more about what the specific needs of the tomato plant are (NPK, micro- and macro- nutrients, timing of fertilizer… should we change fertilizers once they start producing flowers, etc. etc.).
How to avoid tomato splitting in the rainy season? Is it just best to grow tomatoes in hoop-house conditions?
Thanks so much, in advance, for your willingness to help!
~Sarah
You will need to grow either a locally adapted variety or one like Tropic VFN or Homestead or Neptune or Matt’s Wild Cherry that was either bread for or originated in the humid tropics. Even so, you will probably have better luck growing them during the winter months. You are also correct that they are heavy feeders and do best with an abundant supply of all three - NPK. In addition they need particularly high available soil Calcium, which means that the calcium must be present and the soil needs to be mildly acidic so that the plants can absorb it. Otherwise you get blossom end rot, especially during the rainy season.
Since Ca neutralizes pH, how do you get both high Ca and slightly acid soils? We are rinsing, drying and grinding egg shells and adding them to a rotating composter. Will the compost be acidic enough to keep the calcium “available” or will it neutralize the acidity?
I am looking for advice, too, because I have not had any luck with tomatoes in the tropics myself, although in Haiti I had team members who did amazing things. Now we live outside of San José, CR at approximately 1400 m a s l and we had three volunteer tomatoes volunteer in a large pot full of rich organic soil. I thought we had it made (lower temperatures, dry season) but bottom end rot and viruses killed them all before we got even one tomato.
One question for Sara–what elevation are you at in Chinandega and do you have any of the data about average monthly temperatures?
Oh, and I guess I do have one bit of practical advice from experiences of the team members in Haiti. Grow marigolds along with the tomatoes, intercropped, or use them as part of the rotation. Tomatoes are highly susceptible to all kinds of nematodes and marigolds can help suppress many different species. In Haiti, my friend Moccéne had excellent success incorporating the biomass into the soil that had been highly infected with nematodes. What I just read is that the living roots, in the vegetative phase (before flowering) are the most effective at controlling nematodes, but incorporating the biomass does help some, improves organic matter and increases activity of certain nematode pathogens. Protecting crops from nematode pests: Using marigolds (PDF download)
ECHO’s Walter tomato grows very well here in the subtropics with little care. Tropic and cherry varieties also grow well and Roma and san marzano in ‘winter’. We also have a clear plastic shelter (roof only) over them which means we can grow them all year round whereas before that they would just rot in the wet season.
Here are some things to consider in organic tomato production.
I prefer wide spacing, very wide spacing up to 5 or more feet apart per plant. You can fill the space with a crop like onions which allow more air to flow which dries out the leaf faster.
Planting borders or edges if farming on a small scale is great because this is where the air flows most quickly.
Crop rotation and avoiding areas with Sodom Apple is important.
Mulch with clean (no dirt) thick (2 inches) will suppress weeds and conserve moisture.
Begin pruning lowest leaves and branches, particularly those touching mulch and stake when gets 12 or more inches tall. Use chlorine or alcohol solution to sterilize every few plants or you will spread disease. Pruning and leaf removal
Is not needed as much in the dry season.
I use wood ash one or two teaspoons at higher pH and at lower pH one or two tablespoons or charcoal dust or by product from charcoal production. Charcoal dust or debris does not change the pH much so you can add more.
Never enter when wet, work with youngest plants first.
Consider Single row tunnels with plastic you can raise when the clouds get dark before rain and lower the rest of the time. If you are raising in a hoop house plant only the very highest value crops to recoup your investment.
Tomatoes are not heavy nitrogen feeders and too much nitrogen is not good (favors vegetative growth over fruit production). I use human urine for fertilizer but that could be for smaller to intermediate size growers. This gives me a balanced fertilizer with micronutrients.
Using the same planting hole each year has advantages if you ameliorating the soil in the planting hole if using hand labor.
When growing transplants use soil which is high in organic matter but not high in nitrogen. You want your transplants to grow slowly so they can have thick stems. Too much shade in nursery bed reduces potential to survival in the field, but shade after transplanting greatly increases survival or reduces transplant shock. The transplants grown in a nursery bed should be kept more on the dry side to stress them and exposed to as much sun as possible the last 2 or three weeks before planting. A little manure tea is great at planting time. Then a couple weeks after transplanting start fertilizer such as urine or other. Too much shade is not good.
Wilting diseased areas should be isolated and not hoed or walked through if possible because this spreads the disease
These are the methods I teach here in South Sudan and are based on personal experience.
Yes urine is an awesome fertiliser and I also use the charcoal dust. If I need to make it more acidic after adding lime or ash I use coffee grounds which I guess is only helpful where coffee beans are used.
Wow! Thank y’all so much. This is all great information!
@John_Rancken Excellent! Great point about the tension there between Calcium and acidity there.
@Mark, we’re almost at sea level where I’m working and average at 90 or above almost all-year-round, although there are pockets of higher elevation/remaining forest that push those temps down a bit more into the 80s. Great point about the marigolds! We haven’t had a lot of trouble with nematodes so far, but I’ll definitely keep that in mind if we do start to have problems.
@lara_wieland Good to know about those varieties! We’ve had luck using hoop-houses as well. When you added coffee grounds, how do you incorporate them into the soil? Just surface or did you side-dress?
@Dan_Janzen Wow–awesome advice. I love the idea of intercropping onions. Tell me more about Sodom Apple–I haven’t heard of that before. As far as pruning suckers or just letting them do their thing without pruning, what do you tend to do? Love that point about human urine. The guys never use our restroom facilities, so maybe I’ll just direct them over to the tomatoes. On a practical side, how do y’all manage the application of human urine? Do you collect and then apply or direct?
Sodom apple has yellow fruits and resembles an eggplant, actually just a wild type of eggplant but it carries the disease in the soil like other solanum weeds. In the rainy season I prune them if you have a history of trouble with blight and in the dry season I often don’t prune them unless there is a blight problem from overhead irrigation or careless splashing of dirty water onto the plant from improper mulching and I don’t plant them that far apart. I apply the urine in the rain, particularly if I am trying to avoid others detecting I am using it and avoid the smell. No smell–it will not bother people much. Most people collect urine at night but if you need lots of it you collect at any opportunity and others can contribute too. It was a traditional fertilizer that even the poor people could make a little money from selling to the farmer. I apply it straight during rain events but others mix with water, still others just use less but when there is no rain then there is some smell and also potential burning and getting it on leaves or root crops is objectionable if those parts are consumed.
I’m sure there are better ways but I am a lazy gardener so I just pour the diluted grounds around the tomato plants. Digging them into the soil is probably better though.