Legume before rice: lifting Philippine paddy yield

Growing a legume before rice raises the following rice crop's yield by about 15.7 percent and lets you cut synthetic nitrogen substantially. A global meta-analysis of legume-rice rotations across 1,483 data pairs found a 15.7 percent yield advantage in the rice that follows a legume, compared with rice without that rotation. The legume fixes nitrogen and feeds the soil, so the rice starts on richer ground. For Philippine paddy farmers, this is a way to lift yield and trim fertiliser cost at the same time. Here is how it works and how to put it into practice.

How much does a legume before rice raise yield?

A legume before rice raises the next rice crop's yield by about 15.7 percent on average, based on a global meta-analysis of 1,483 paired comparisons of legume-rice rotations. That figure is an average across many sites and systems, so your result will vary with soil, the legume used, and how well it is grown and incorporated. But the direction and size of the effect are well supported across a large dataset: rice following a legume reliably outyields rice that does not. The gain comes mainly from the nitrogen and organic matter the legume leaves behind.

How much synthetic nitrogen can I save?

You can cut synthetic nitrogen substantially when a legume green manure precedes rice, with the rotation research showing synthetic nitrogen reduced from around 100 kg N per hectare to about 40 kg N per hectare while maintaining yield. That is a large saving on fertiliser, because the legume has already fixed and supplied much of the nitrogen the rice needs. The exact reduction depends on how much biomass the legume produced and how well it was incorporated, so treat the 100-to-40 figure as what is achievable under good green-manure management rather than a guarantee. Even a partial cut in nitrogen fertiliser is real money saved per hectare each season.

Why does a legume rotation also help the soil?

A legume rotation helps the soil by adding nitrogen, organic matter, and carbon, which builds fertility beyond the single following crop. The legume-rice rotation research found these rotations increase yields and soil carbon globally, not just the next rice yield. Fixed nitrogen feeds the rice; the legume residue adds organic matter that improves soil structure, biology, and the soil's capacity to hold nutrients and water. Over repeated cycles this compounds: better soil supports better crops with less external input. So the benefit is both immediate, the yield bump and nitrogen saving on the next rice, and cumulative, a soil that gets steadily healthier.

How do I fit a legume into a Philippine rice system?

Fit a legume into the fallow or off-season window before rice, grow it for biomass, then incorporate it as green manure ahead of transplanting. The practical sequence is: sow a suitable green-manure legume in the gap before the rice crop, let it grow and fix nitrogen, then turn it into the soil before it sets seed so the nitrogen-rich biomass breaks down for the rice. Time the incorporation so the residue has begun decomposing when the rice goes in. Inoculate the legume seed with the right rhizobia on acid soils so it fixes nitrogen well. Then reduce your nitrogen fertiliser to reflect what the legume has supplied, and watch the rice over the season.

FAQ

How much more rice will I get after a legume?

On average about 15.7 percent more, based on a global meta-analysis of 1,483 paired comparisons of legume-rice rotations. Your result varies with soil, the legume, and how well it is grown and incorporated, but rice following a legume reliably outyields rice that does not, mainly because of the nitrogen and organic matter the legume leaves behind.

Can a legume green manure replace my nitrogen fertiliser?

It can replace a large part of it. The rotation research shows synthetic nitrogen reduced from around 100 to about 40 kg N per hectare while maintaining yield when a legume green manure precedes rice. The actual saving depends on how much legume biomass you grow and incorporate, so treat it as achievable under good management rather than guaranteed.

When should I incorporate the legume before rice?

Incorporate the legume as green manure before it sets seed and ahead of transplanting, timing it so the nitrogen-rich biomass has begun to decompose when the rice goes in. This releases the fixed nitrogen and organic matter into the soil for the rice crop. On acid soils, inoculate the legume seed first so it fixes nitrogen well.

Get green-manure legume seed for your paddy rotation

We supply green-manure and cover-crop legume seed tested to ISTA and AOSA methods, with inoculation advice for acid soils, to fit a legume into your rice rotation. To get seeding rates or request a quote, message us on WhatsApp at +60 17-237 4058.

Sources

• Legume-rice rotations increase yields and carbon globally, ScienceDirect: https://www.sciencedirect.com/science/article/pii/S2590332224006006
• Global meta-analysis of yield advantage of legume rotations, PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC9395539/