July 21, 2006

7-21 El Experimento: The Cavalry Arrives

Yesterday my experiment finally got off the ground. (You didnít think I came down here just to take pictures of bugs, did you?) Now thereís nothing to do for this part of my work here but to water the nursery bags and wait. Also, some pesticide will be sprayed around the greenhouse where the experimental blocks are set up. Iím not super thrilled about this, but lettuce isnít a native plant and it has little in the way of defenses for what can ail it around here. I didnít need much arm twisting. At this point Iím only going to be able to get about three and a half weeks worth of growth data even in the best case.

The bugs canít have these 192 plants.

Lettuce and radishes were chosen for, as shouldnít be surprising, their rapid growth. Each of three soil mixtures and a control with nothing but bare soil were to be added to 48 plastic nursery bags, with 24 planted in lettuce and 24 in radish. The lettuce got blue popsicle sticks and the radish, white. The soil treatments each got either green, yellow or red popsicle sticks, while the control bags only got a marker for the type of plant. Six lettuce and six radish bags from each treatment were then set into each of four groups that were packed back next to each other in a way that, if not exactly random in the proper sense, at least mixed up the treatments and the types of plants fairly well.

First though, the seeds had to be tested. Last Friday I set up rows of 100 seeds from each of four bags of seed on a layer of wet paper towels with another layer of wet paper towels laid on top. I got two bags each of radish and lettuce seeds, just in case Iíd ended up with a bum pack of seeds. The nearest agrochemical/garden supply store is 45 minutes to an hour away by bus and thereís a driversí strike going on right now, which means the route is down to two inconveniently timed buses a day. If they succeed in lobbying for some road repair, Iíll be cheering, but maybe not so much if they negotiate a fare increase. The seeds needed to germinate at a rate better than 80% to be useful for an experiment, so that any growth failure canít be attributed to the seeds.

Both radish packs had four failures and one seed that was growing significantly slower than the others. There were four failures in one of the lettuce packs and none in the other. I was so thrilled by the success rate of the second lettuce test that I just had to take a picture. For the planting, I used seed from the super lettuce and the pack of radish seeds whose sprouts seemed slightly more vigorous in terms of color and size than the other. Both of the better performing packs were from the lower of the two shelves I used and I donít know if that made any difference, but all the packs performed well enough to be useful. Leftover seeds have gone to good homes.

Radish seeds on trial. Finca Montezora, Costa Rica, 7-14-06 Ė natashaGermination rate trial. Finca Montezora, Costa Rica, 7-14-06 Ė natashaLettuce sprouts. Finca Montezora, Costa Rica, 7-17-06 - natasha

Next, the soil and treatments had to be prepared. It was suggested to me that I should get a mix of soils from around the area and combine them for use as a base soil in order to avoid biasing the results by using only one type of soil. This sounded like a great suggestion until I realized that for me, it would mean walking all over the area, up and down steep gravel roads in the heat of the morning, enough times to drag a range of soil samples back to the test site at the rate of one or two plastic grocery sacks full at a time. Did I mention that itís pretty humid here and the mountain air is a bit slim in the oxygen department? If I ever repeat this or a similar experiment and have enough funding to rent a truck, or even a pack horse, Iíll try getting more of a range of soils for trials.

Edge of the greenhouse and accompanying soil tested field. Finca Montezora, Costa Rica, 7-20-06 Ė natashaSifting the soil. Finca Montezora, Costa Rica, 7-20-06 - natashaFor this occasion, a field at Finca Montezora thatís had soil testing performed by a government lab is the sole donor. The soil was sifted through a screen to minimize roots and large insects before being measured into bags for the different treatments. The control trial should be a good indication of how much of the results depended on the base soil, low in phosphorus and potassium with a pH of 5.4, and Iíll hope thatís enough.

Weighing the soil. Finca Montezora, Costa Rica, 7-20-06 - natashaMy estimates for the percentages of large quantity additives were based on the weight of a filled nursery bag multiplied by 48. The other additives were obviously going to differ in terms of porosity and density, and there were leftovers from all the treatment mixes, but weight as calculated by a hanging milk scale is what I had to go by.

The bagged charcoal was pulverized by sledgehammer, the unfortunate bones from the carbonera experiment plus a few extra were torched thoroughly and then pulverized, then the individual treatments were mixed by shovel on a concrete barn floor that was as clear and uncontaminated a surface as was available.

Burned bones. Finca Montezora, Costa Rica, 7-20-06 Ė natashaPulverizing the charcoal. Finca Montezora, Costa Rica, 7-20-06 Ė natashaMixing the treatments. Finca Montezora, Costa Rica, 7-20-06 - natasha

Then the bags were filled, the seeds planted and the bags thoroughly mixed up with each other. By the time this was finished, the rain wasnít just hard, it was vengeful. The wind was blowing spray even into the center of the greenhouse and we all had to wait in the barn for a lull before heading back to the house. This was one of the other holdups getting everything started, not only navigating the weather but needing shelter for the plants. The Finca Montezora greenhouse was the only one anybody Iíve talked to knew about that didnít need new plastic for the roof, which would have had to come from San Vito by bus.

This project wouldnít have been possible without the help of the people at Rudolfo Arayaís Finca Montezora and his kind offer of the use of the facilities there. Iím very grateful for all their assistance.

Posted by natasha at July 21, 2006 11:41 AM | Costa Rica | Technorati links |