Green Manure & Cover Crops for Philippine Rice | Kudzu Seeds Trading
Green Manure and Cover Crops for Philippine Rice
Kudzu Seeds Trading supplies tropical legume green-manure seed to Philippine rice growers in Cagayan Valley, Central Luzon (the rice granary), Western Visayas, Ilocos, and Bicol. A 60-to-90 day green-manure rotation before transplanted rice can supply 30 to 50 kg of nitrogen per hectare to the following crop, reducing the imported urea bill.
At a glance
- PH role: Rice is the staple food crop of the Philippines, with planted area concentrated in Central Luzon, Cagayan Valley, Western Visayas, and Ilocos.
- Institutions: The Philippine Rice Research Institute (PhilRice) leads PH rice research; the National Irrigation Administration (NIA) manages major irrigation systems.
- Green-manure benefit: Mucuna, Pueraria, Crotalaria, Sesbania, and Vigna grown as a 60-to-90 day rotation can supply roughly 30 to 50 kg of biologically fixed nitrogen per hectare to the next rice crop.
- Rotation context: Green-manure cover fits between the dry-season harvest and the wet-season transplant window (April to June) on irrigated land, or in the post-wet-season fallow on rainfed land.
- Primary species: Mucuna bracteata (MB), Pueraria javanica (PJ), Calopogonium mucunoides (CM).
Why green-manure cover crops matter for rice in the Philippines
The Philippines imports a large share of its synthetic nitrogen fertiliser as urea. Every kilogram of biologically fixed nitrogen that the soil delivers to the rice crop displaces a kilogram of imported urea. Across the 60-to-90 day fallow window between dry-season and wet-season rice (or between rice and the next planting on rainfed bunds), a tropical legume green manure can supply 30 to 50 kg of nitrogen per hectare to the following crop, depending on species, biomass, and incorporation method.
PhilRice and the broader irrigated-rice research community have long documented the agronomic value of legume green manure: Mucuna, Crotalaria, Sesbania, and Vigna species (mungbean, cowpea) have been studied in PH rice rotations for decades. Tropical climbing legumes like Mucuna bracteata, Pueraria javanica, and Calopogonium mucunoides extend that toolkit, especially on the rainfed and upland-rice systems where ground cover and erosion protection also matter.
The second value-driver is soil structure. Legume root systems and biomass turnover build organic matter on continuously cropped lowland rice soils, which would otherwise mineralise organic carbon under repeated puddling. Periodic green-manure rotations are a recognised counter to long-term soil organic matter decline in intensified Philippine rice systems.
Recommended species for Philippine rice rotation
Mucuna bracteata (MB)
Highest-biomass option for green-manure rotations on irrigated or rainfed bunds. Nursery-raised seedlings at around 320 per hectare (about 85 to 100 g seed per hectare). 67 to 84 percent Ndfa, around 150 to 200 kg N/ha/yr in standing biomass; a 60-to-90 day window in rice rotation will return a share of that to the next crop on incorporation.
Best biomass · transplanted, not broadcast
Pueraria javanica (PJ)
Broadcast 4 to 6 kg per hectare. Fast-establishing tropical climber for rainfed rice fallows and rice-upland transitions. Good ground cover with moderate biomass return.
Rotation crop · 4 to 6 kg/ha
Calopogonium mucunoides (CM)
Broadcast 6 to 10 kg per hectare. Pioneer for acidic and degraded rice land, including the upland fringes of Cagayan Valley and Bicol where Ultisols are common.
Pioneer · 6 to 10 kg/ha
Centrosema pubescens (CP)
Broadcast 4 to 6 kg per hectare. Persistent legume for paddy bunds, headlands, and irrigation canal banks. Rebuilds organic matter on edges where the rice crop does not reach.
Bunds and edges · 4 to 6 kg/ha
Calopogonium caeruleum (CC)
Broadcast 4 to 6 kg per hectare. Climbing legume for sloped upland-rice systems and rainfed margins.
Upland margins · 4 to 6 kg/ha
SoilBoost EA
Humic acid soil conditioner: 60.6 percent humic acid (CDFA method), 0.45 percent sulphur, pH 3.84. Broadcast 50 to 100 kg/ha at land preparation, or drench 10 to 15 kg/ha. Supports soil biology in continuously cropped lowland rice soils. Manufactured exclusively by Chemiseed Sdn. Bhd.
Amendment · supports soil biology
PH-specific establishment timing
Philippine rice runs two main calendars: irrigated double-cropping (dry season + wet season) and rainfed single-cropping (wet season only). Green-manure timing follows the available fallow window.
- Irrigated Central Luzon and Cagayan Valley: after dry-season harvest in April to May, broadcast PJ or CM (or transplant MB seedlings) into the fallow. Incorporate at land preparation in late June or early July before wet-season transplanting.
- Rainfed Western Visayas and Ilocos: after the wet-season harvest in November to December, the fallow window is short and dry. PJ and CM established with residual moisture can carry through to the next wet season's transplant; CP and CC make better bund-edge perennials.
- Upland rice (Cordillera, parts of Bicol, Mindanao): establish CM or PJ ahead of the rice crop as a true rotation, ploughing in two to three weeks before sowing.
Central Luzon and Cagayan Valley sit in the Type I climate with a pronounced dry season, suiting a short, fast green-manure rotation. Bicol, eastern Visayas, and parts of the Cordillera carry rain through more of the year and need timing that avoids saturated incorporation.
Common challenges in Philippine rice
- Imported urea cost. Biological N fixation from a green-manure rotation supplies 30 to 50 kg N/ha to the next rice crop, reducing the synthetic N requirement.
- Soil organic matter decline under intensified double-cropping. Periodic legume green manure rebuilds organic carbon between rice crops.
- Weed pressure in fallow paddies. A dense legume cover suppresses Echinochloa and other weed seedbanks compared with bare fallow.
- Acidic upland and rainfed soils. CM is the standout pioneer on the most degraded rainfed and upland-rice plots; SoilBoost EA supports nutrient availability where humic substances are depleted.
- Typhoon and flood exposure. Established legume cover on rice bunds and rainfed margins holds topsoil during high-rainfall events better than bare ground.
Frequently asked questions
How much nitrogen does a green-manure rotation supply to Philippine rice?
A 60-to-90 day tropical legume green-manure rotation (Mucuna, Pueraria, Crotalaria, Sesbania, Vigna) can supply roughly 30 to 50 kg of biologically fixed nitrogen per hectare to the following rice crop, depending on species, biomass, and incorporation method. This is a meaningful share of the typical 90-to-120 kg N/ha requirement for transplanted rice and directly reduces imported urea.
Which species fit best between dry-season and wet-season rice?
For the April-to-June fallow on irrigated land in Central Luzon and Cagayan Valley, Pueraria javanica (PJ) broadcast at 4 to 6 kg/ha establishes quickly. Calopogonium mucunoides (CM) at 6 to 10 kg/ha works on more acidic blocks. For higher biomass on longer fallows, Mucuna bracteata (MB) transplanted at around 320 seedlings per hectare delivers the largest nitrogen and biomass return.
Can I use legume cover crops on rainfed rice?
Yes. Rainfed rice systems in Western Visayas, Ilocos, and parts of Mindanao benefit particularly from legume cover because the off-season fallow is long enough to produce real biomass before the next crop. CM and PJ established with residual moisture in the closing rains carry through to the next planting cycle.
How do I incorporate the green manure before transplanting rice?
Standard practice is to plough or rotary-till the legume cover into the wet soil two to three weeks before transplanting. The incorporation window lets biomass start breaking down and nitrogen begin mineralising. Heavy biomass (Mucuna) may need an extra week. Avoid incorporating immediately before transplanting because freshly buried green matter can immobilise nitrogen short-term.
Do you deliver to Central Luzon, Cagayan Valley, and other rice regions?
Yes. Kudzu Seeds Trading dispatches from Davao City and consolidates Luzon orders through Manila. Seed ships under a phytosanitary certificate from the Philippine Bureau of Plant Industry (BPI) for inter-island movement. Bulk-order quotations are available for cooperatives, irrigators' associations, and PhilRice extension partners.
Related pages
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