Fertilization can be tricky

Almost all the seedlings survived so far , many of them starting developing the third leaf. We noticed that in some rows of a couple of plots, there were 2-5 seedlings planted together. We separated every individual seedlings when uprooting them from the nursery, so it was definitely not due to difficulty of taking them apart. Our transplanting team was a mix of iF Foundation staff and hired local farmers. It is possible that the farmers did not completely follow the “single seedling” transplanting technique because they might not understand SRI concepts. We went through all the plots to thin the seedlings and replace a few weak ones.

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(3 seedlings planted at the same hill, 2 of which were removed later.)

I was planning to incorporate compost during land preparation, but after learning how people prepare the land, I figured out that it might not be a good idea. The land preparation includes overturning soil, flooding, puddling, and leveling. The soil is 30-40 cm deep. There would be a big chance that the compost would be washed away or stirred deep down that the young roots could not reach. We were to apply compost around March 28th, right after transplanting. Yet we got heavy rain over the nights of March 26 and 27. The plots were a bit flooded. We spent much time opening more drainages for the plots on the 28th. We left the field to dry over the weekend.

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(Draining the plot)

We came back to the field on Tuesday, April 1, to check the soil moisture condition. It was kind of trick. The soil seemed to be very dry as there were cracks on the surface. I stuck my finger into the soil, and it was actually moist inside. The water table did not fully drop back. The surface was kind of firm, like a soft crust, and it was not really difficult walking on it. The soil was diagnosed as a heavy clay vertisol by USDA scientists in an earlier soil survey. The surface cracks easily once it starts drying. I think it is actually beneficial for the SRI plots to have this cracks because the openings allow soil aeration and create a channel for nutrient absorption. Otherwise the compacted surface will block out oxygen and slows down the diffusion of additional soil nutrients from compost into the soil.

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(Soil cracks when it starts to dry)

The majority of the seedlings looked yellowish, and they really need some nutrient. We decided to slightly water the plots to soften the surface so that it would be easier for nutrients to get into the soil. We were planning water them Wednesday morning, but there was a thunderstorm on Tuesday night. We were worried about flooding, but we found that the water drained well. All the plots were moist but not submerged. Considering the fact that it has been 10 days after transplanting, and compost releases nutrients slowly, we agreed on putting some nitrogen fertilizer for them to facilitate establishment. On Wednesday afternoon we spread 2.5 kg nitrogen fertilizer (40:0:0
) to the SRI plots, about 3.5 g per square meter, as a bit “fast food” for them. We planned to apply compost soon afterward as a continuous nutrient supply. A major challenge for soil fertility management here is that there is no weather forecast service in this area, probably even no such thing countrywide. We have no idea when there will be a precipitation, how much it will probably rain, how much area it will cover, and how long it might last, etc. We completely rely on observation of cloud and assumption. A medium to heavy rain can wash away any kind of soil nutrient amendment, which is our biggest concern. We have been postpone applying compost because there have been nimbus every afternoon.This is another reason why we drizzled just a little bit N fertilizer–compost and extra chemical fertilizer will be gone when water draining out from the plots. We hoped that the chemical can dissolve and be taken up fast enough before the field hit by another heavy rain. Fortunately there was not much rain that night.

This morning we eventually applied compost to all the SRI plots. It did not rain last night and the sky is clear today. All the plots were moist, and soil has been softened.  We used vermicompost produced at the iF Foundation, and spread 10 kg on soil surface in each plot.

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(SRI plot fertilized with vermicompost)

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(seedling at 3-leaf stage)

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