simple living, home grown food, clean air

sunn hemp as green manure


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We broadcast sunn hemp (crotalaria juncea) seeds on our rice field about six weeks before the rice is due to go in. We do it for two main reasons, it is a green manure that fixes nitrogen in the soil and produces a lot of biomass and it also has the welcome side effect of not allowing any weeds to establish after the field has been ploughed. We have been doing this every year before planting.

This time we tried a couple of ways to sow the seeds without turning the soil, but with little success. First we just broadcast them without digging or turning, but germination was very patchy, then we tried seeding in rows after manual digging but this proved way too slow and labour intensive, so we resorted to the tractor. I have not given up though and am determined to find a way….

This week we will cut down the fields and flood them and let the biomass decompose in the water for a couple of weeks, after which the fields will be prepared for rice planting. Last year we experimented with the SRI (System of Rice Intensification) system on a small area, transplanting individual seedlings when they are about a week to ten days old as opposed to the traditional way of planting clumps of five or more one month old seedlings. The results were very encouraging, so this year we are confident about using the system for our entire crop, which will allow us to control the water level more appropriately as required by the system.


Author: marco

growing food and making do with less

4 thoughts on “sunn hemp as green manure

  1. Marco, how is the SRI going this year? We’re interested in learning about people’s experience with SRI, Also, I’d be interested in knowing how you heard about it… Thanks for mentioning our website in your post. Also, here’s a new SRI news format we’re trying out:

    • Hi Lucy,

      Thank you for your message. Difficult for me to say much as far as yield is concerned as I am not an experienced rice grower. We heard about SRI through ECHO, an agriculture NGO from Florida who have an office in Chiang Mai and do many types of ag extension work in this area, they have been promoting it for years with mixed results.
      We started two years ago with a small patch, did all our fields the SRI way last year and just planted again this year.
      Slowly we are perfecting a number of details, this year we have been much more rigorous with the planting as last year we had to weed by hand and it was very time consuming and therefore expensive, we have acquired a CONO weeder and planted the seedlings 30 to 40cm apart in very straight lines.
      Another advantage this year is that the people who helped us with the planting are our regular workers and so they are more receptive to our requests, it would be difficult to do the same job with people that have never seen the technique before and are used to the traditional way, they think it is very slow and fiddly, which is true to an extent.
      From what I have heard there are a number of farmers planting SRI in central Thailand and they are developing a number of tricks and tools to render the process easier and faster.
      Last year we grew a 40 day green manure crop of crotalaria and planted 10day old seedlings, we used only a little cow manure and our own compost twice during the growing period, roughly 100/150 kg per acre, we never actually calculated it exactly.
      All our neighbours seemed to think our rice was very good, but I am not sure much can be read into it as there could be many variables.



  2. Where can I get Sunn Hemp seed from?

    • It tends to be available for free around April/May at local govt. agricultural extension offices. Or alternatively large commercial seed suppliers for around 1200B per 20kg.

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