By June, habagat rains arrive across Luzon and Visayas. On hilly terrain (the uplands of Benguet, sloped sectors of Nueva Ecija, banana plantations in Davao, coconut in Quezon), those weeks can strip topsoil, taking plant-available phosphorus, potassium and organic matter downslope. On hilly land in the Philippines, erosion plots under conventional farming lost 100 to 200 tonnes of soil per hectare per year (Paningbatan et al., 1995). The farm downstream gets richer. Yours thins. By August, yield is already compromised.
This is not a soil health essay. It is a statement of fact: soils rich in organic matter and kept under cover hold together through rain. Bare or thinly vegetated soils do not. And if your farm has been bare through April and May (fallow after harvest, before replanting, or cleared for new planting), you are losing the window to prevent the damage.
Why Topsoil Leaves Your Farm
Soil particles move when rain energy exceeds aggregate stability. On bare or fallow ground, the topsoil, where much of the phosphorus and potassium sits, has no protection from raindrop impact. A few intense storms can do most of the damage: on a 42% slope on volcanic-ash-derived soil in the Philippines, three rain events caused 47% of the total soil loss measured from 1995 to 1998 (Poudel et al., 1999). Soils low in organic matter have weaker aggregates and lose soil faster.
The cost of that loss is not just erosion; it is nutrient export. Sediment carries phosphorus, potassium and organic matter away, and most upland farms do not replace them. They mine soil year after year.
This happens fastest on upland rice, maize, or newly cleared coconut blocks. It happens on ratoon sugarcane where residue is removed for fuel. It happens on banana blocks where inter-row cultivation exposes soil. It happens anywhere roots and cover do not protect the topsoil through the wet season. By the time habagat arrives, the damage is largely decided by what you did or did not do in April and May.
Dense Cover Slows Runoff
Pueraria (PJ) grown as an intercrop or off-season cover crop takes months to close: in Malaysia, PJ reached 60 to 70% ground cover after about 4 months and 90 to 100% after 8 months (PROSEA 11). Mucuna bracteata (MB), drilled or planted in holes or raised as nursery seedlings, forms a dense, high-biomass cover once established. Ground cover intercepts raindrops before they hit bare soil, and roots and residues help water soak in rather than run off.
In a small plot study under 3-year-old oil palm in Riau, Indonesia, erosion in April averaged 26.44 t/ha without MB and 9.25 t/ha with MB (Wawan et al., 2019). The study had only two replicates and covered a few months, so treat it as an indication rather than a forecast. Contour barriers add to the effect of cover: on the Philippine hilly-land plots above, alley cropping with contour hedgerows cut soil loss to less than 5 t/ha per year (Paningbatan et al., 1995).
Keeping soil in place is far cheaper than trying to rebuild eroded topsoil, which may not be possible at all. A cover crop also protects soil depth and long-term productivity.
Where SoilBoost EA Fits
Even under cover, some rainfall percolates. Potassium and nitrate are mobile in soil solution and can leach, especially on sandy or low-organic-matter soils. Soil organic matter raises cation exchange capacity, which helps the soil hold cations such as K⁺ and NH₄⁺. SoilBoost EA is a humic acid soil conditioner that may support soil structure and root-zone conditions as part of that programme; no published trial has measured its effect on leaching or erosion in Philippine fields.
Our only trial data for SoilBoost EA come from a company-commissioned trial at PCA-Davao on banana seedlings, registered to Kudzu Seeds Trading under FPA Experimental Use Permit No. 3227. It was not an erosion or leaching trial, so test the product on your own blocks before you rely on it.
Five Steps for May Preparation
1. Map sloped blocks. Use phone GPS or visual inspection. Mark sloping blocks on a map or in your notebook. If you have satellite view on Google Earth or similar, you can see slopes from shading. Prioritize the steepest blocks first.
2. Establish Mucuna bracteata or pueraria before the habagat rains set in. Drill the seed or plant it in holes. Recommended seeding rates, each for one species sown alone (our recommendation): pueraria 10 kg/hectare, Mucuna bracteata 1 kg/hectare. Broadcasting does not guarantee good germination, especially where the soil dries out easily. Mucuna bracteata can also be raised in a nursery and transplanted; in MPOB's trial on deep peat, 320 seedlings/hectare, two per palm point, were raised from about 500 seeds (75 g) (MPOB TT No. 501). No tillage if possible; this saves labor and avoids further soil disturbance. Rain will germinate seed sown in the field if the soil is moist. Because PJ takes months to close, the earlier you sow the better; on the steepest ground, mulch and contour barriers give protection while the cover establishes.
3. If you use SoilBoost EA, apply it before cover crop sowing at the rate on the product label or your quotation. Do not apply to standing water or waterlogged soil.
4. Mulch if available. Rice straw, banana trash, sugarcane trash, or coir over the cover crop root zone adds another physical barrier and slows water movement down the slope. Even a thin layer of dry mulch cuts evaporation and protects the legume seedlings from raindrop impact. If mulch is not available, avoid disturbing the young legume stand.
5. Monitor gully development through the wet season. Check if water is cutting channels or if rill erosion is visible. If so, place contour lines of coconut fronds, cut branches, or logs across the slope to catch sediment; on steep plots in Leyte, contour hedgerows approximately halved runoff (Presbitero et al., 1995). Small intervention now saves labor later and prevents active gullies from becoming permanent features.
This Is Not Optional on Steep Ground
Sloping farms lose productivity every wet season they stay bare, and lost topsoil does not come back on a farming timescale. Rehabilitating eroded terraces or bringing in replacement soil is costly. A cover crop, contour barriers and mulch are the low-cost defense, and they help prevent the irreversible damage of a gully that has to be filled or bypassed. Request a quote for cover crop seed and SoilBoost EA for your crop and hectarage.
Timing matters. May is the month to act. If you wait until June, the heavy rains have already arrived and any erosion from June rains cannot be prevented. Start this month if you have not already. If you planted rice or another crop in April, you still have time between crop rows if the spacing is wide enough. Even scattered legume is better than bare soil.
References
Halim, R.A. (1997). Pueraria phaseoloides (Roxb.) Benth. In: Faridah Hanum, I. & van der Maesen, L.J.G. (eds), Plant Resources of South-East Asia No. 11: Auxiliary plants. Backhuys Publishers, Leiden. Reproduced on Pl@ntUse: Pueraria phaseoloides (PROSEA)
Hasnol Othman, Farawahida Mohamad Darus & Zulkifli Hashim (2012). Best management practices for oil palm cultivation on peat: Mucuna bracteata as ground cover crop. MPOB Information Series 588 / MPOB TT No. 501. Malaysian Palm Oil Board.
Paningbatan, E.P., Ciesiolka, C.A., Coughlan, K.J. & Rose, C.W. (1995). Alley cropping for managing soil erosion of hilly lands in the Philippines. Soil Technology 8(3): 193-204. https://doi.org/10.1016/0933-3630(95)00019-4
Poudel, D.D., Midmore, D.J. & West, L.T. (1999). Erosion and productivity of vegetable systems on sloping volcanic ash-derived Philippine soils. Soil Science Society of America Journal 63(5): 1366-1376. https://doi.org/10.2136/sssaj1999.6351366x
Presbitero, A.L., Escalante, M.C., Rose, C.W., Coughlan, K.J. & Ciesiolka, C.A. (1995). Erodibility evaluation and the effect of land management practices on soil erosion from steep slopes in Leyte, the Philippines. Soil Technology 8(3): 205-213. https://doi.org/10.1016/0933-3630(95)00020-8
Wawan, Dini, I.R. & Hapsoh (2019). The effect of legume cover crop Mucuna bracteata on soil physical properties, runoff and erosion in three slopes of immature oil palm plantation. IOP Conference Series: Earth and Environmental Science 250: 012021. https://doi.org/10.1088/1755-1315/250/1/012021