Anyone?

Ceth, the plants looked very healthy at 25 days... so the question would be, what changed after that time?

It sounds like bad weather is the most likely explanation for the chlorosis. Yardlongs thrive in heat & full sun, and plentiful moisture... as long as the soil is well drained. Cool nights & excessively cloudy days would slow them down.

As a rule, beans don't need nitrogen, so I would avoid applying manure around them. Fresh manure, in particular, can cause root damage.

Applying wood ashes directly to the soil around living plants is generally not a good idea. The ashes are highly alkaline, and can burn roots. But your observations make me wonder. Tropical soils are often acidic (low pH) and wood ashes would increase the soil pH. If you can test your soil pH, I would recommend doing so. Wood ashes in moderate amounts would help to neutralize acidity, but the best time to apply them would be to dig them in several weeks before planting, which would hopefully give them time to dissolve.

I grow many different yardlongs here, most are varieties from Southeast Asia or the Philippines. Those that are not daylength sensitive generally do well for me. They only grow when the weather is warm, though; because of my short growing season, I can only harvest beans for a month or two.

While I have been to Southeast Asia many times, and am familiar with your climate, I don't have experience gardening there... so that is the best advice I can offer.

Thanks zeedman.

I would think that sulfur would be the opposite direction to go on ph for you. Wood ashes raises the "sweetness" of the soil, sulfur makes it more acid or "sour". (a quick test kit would tell you for sure which way you need to go.)

My limestone soil is perpetually too "sweet" or too alkaline, so I have to add sulfur to my garden. I notice alot of chlorosis when some extra acid is needed, but unfortunately adding sulfur won't help for the quick fix...just as wood ashes probably wouldn't be for you. These must be added a season ahead of time so the microbes in the soil can break them down and adjust the actual soil ph. For a quick fix for me I add some horticulture grade vinegar to the watering can. For you, I'm thinking you might want to invest in a bottle of PH-UP. This is what nurseries and greenhouses use to adjust the water for their operations. Aquarium people use it too. It's very safe for fish and plants as long as you follow directions.

The point about sulfur is well taken. Sulfur is used to lower pH, such as in my area, where the limestone bedrock typically raises the soil to a pH of 8.0 or above. There is very little sulfur in wood ash, though; the primary component is potassium salts.

Tropical soils are more likely to be acidic (low pH), so the goal would be to raise pH. Wood ashes would accomplish this. If there are pieces of natural charcoal embedded in the ash, so much the better... they will help to increase soil fertility (see "terra preta" soils). My only reservation would be the source of the ash - scrap building materials & commercial charcoal might have additional chemicals which would not be suitable for a vegetable garden.

While I also advise digging ashes into the soil the year before, I believe this has little to do with microbial action. The object is to diffuse the highly-concentrated salts (which can cause root damage in their undiluted form) evenly, so they can neutralize the soil pH throughout the root zone. For you & I, RWS, applying ashes in the Fall accomplishes this naturally over time, as rain & snow melt leech the minerals deeper into the soil. The original poster has a year-round growing season, so this may not be practical for them. Digging the ashes as deeply into the soil as possible (I would recommend double digging), plus several weeks of either rain or irrigation, should spread the ashes well enough to allow planting.