Wheat at 13.8% Moisture with Live Insects and Only 60 Tonnes of Headroom
A CWC godown receives 2,000 bags (100 tonnes net) of wheat from the mandi on 28 September. Moisture tested on the godown's capacitance meter reads 13.8% in 12 of 20 random samples and 12.4% in the remaining 8; the meter was last calibrated 15 months ago. Grain temperature at intake is 35 °C against an ambient of 33 °C and 72% relative humidity. While drawing samples, the helper finds live rice weevils and one lesser grain borer in three of the 20 bags.
The supplier disputes the finding, pointing out that the godown already holds 300 tonnes of wheat fumigated with aluminium phosphide 20 days ago, and says 'the insects must have come from your own stock'. The godown has spare covered space of 40 ft × 25 ft under a 12 ft eave, but its licensed capacity has only 60 tonnes of headroom. The regional office wants a decision the same day, because the supplier threatens to unload outside the gate if the lot is refused.
1. Compute the settled weight if the lot is dried to 12% moisture, and state how the disputed reading should be handled.
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Which figure to use. The lot is not uniformly 13.8%; the sample must be weighted, not judged by its worst bag:
Weighted moisture = (12 × 13.8 + 8 × 12.4) / 20 = (165.6 + 99.2) / 20 = 13.24%
Settlement weight at 12%. Dry matter is conserved; only water is removed.
- Dry matter = 100 × (1 − 0.1324) = 86.76 t
- At 12% moisture the final weight W satisfies W × 0.88 = 86.76 → W = 98.59 t
- Shrinkage = 100 − 98.59 = 1.41 t, about 1.4%
For contrast, settling every bag at 13.8% would give 86.2 / 0.88 = 97.95 t, i.e. 2.05 t - a further 0.64 t deduction that the samples do not support.
But do not sign on this meter. A capacitance meter 15 months out of calibration can drift by half a percentage point, which on 100 tonnes is about 0.6 t of grain. The defensible sequence is: (i) record the weighted 13.24% and issue a provisional weight; (ii) send a composite sample for the oven/reference method at the district laboratory; (iii) adjust the final bill against the reference result. Refusing the lot outright is not justified by moisture alone - 13.24% is storable after drying, and a refusal on an uncalibrated reading would not survive a grievance.
2. Does the lot fit? Work out the capacity and space position and state what should be accepted today.
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Licensed capacity. Headroom is 60 t against a 100 t lot, so 40 t has nowhere legal to go. Storing beyond licensed capacity is not a discretionary call - it breaches the registration under which the godown issues warehouse receipts and would invalidate insurance cover on the excess.
Floor space, as a cross-check. A 50 kg bag footprint is roughly 0.9 m × 0.6 m ≈ 5.8 sq ft. At a 10-bag stack height, 2,000 bags need 200 positions ≈ 1,160 sq ft of pure footprint before dunnage, gangways and inspection alleys, which normally consume 30–35% of a shed. Usable area here is about 650–700 sq ft of a 1,000 sq ft space, i.e. roughly 112 positions ≈ 1,120 bags ≈ 56 t. The space calculation independently confirms the licence figure.
Decision: accept up to 60 t (about 1,200 bags) into the licensed space on a provisional weight, and either (a) obtain same-day written approval to store the balance under tarpaulin in the covered yard, or (b) divert the balance to the nearest CWC godown with capacity and issue a receipt for a part lot. Tell the supplier in writing, before 17:00, that 60 t is being received and the balance is being diverted - the threat to unload outside the gate is a risk to the supplier's own stock, and a witnessed refusal note protects the godown either way.
3. Set out the treatment plan for the insects, including how to answer the supplier's claim about the 300 tonnes fumigated 20 days ago.
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Answering the claim. Phosphine leaves essentially no residual protection once the enclosure is ventilated. A stack fumigated 20 days ago is not 'protected'; it is merely a stack in which a kill was attempted. So the supplier's inference does not follow, and equally the godown cannot prove the insects came in with the new lot. The correct finding is 'live infestation present in the receiving lot, source not established' - recorded on the inspection slip, signed by both parties, with the infested bags retained as evidence.
Sequence, which matters:
- Dry and aerate first, fumigate second. Fumigation of damp grain at 13%+ moisture and 35 °C gives poor gas retention and invites condensation and hot spots; phosphine also acts poorly where grain is crusted. Bring the lot towards 12% and cool it.
- Physically separate the new lot from the existing 300 t and from any other stock until it has been treated; do not share dunnage or tarpaulins.
- Fumigate under gas-proof cover, both the new lot and, as a precaution, any adjacent stack showing live insects, using aluminium phosphide only under a licensed operator, with warning boards, sealing checked with sand snakes, and no occupancy of adjoining space. Exposure for bagged grain is typically 5–7 days at the prevailing 30 °C-plus temperatures, per the approved schedule.
- Verify, then ventilate and record the result; dispose of spent powder as directed and never in a drain or water source.
- Resistance management: do not treat the same stack repeatedly with sub-lethal doses behind a leaking sheet. Poor sealing, not the chemical, is the usual cause of a failed fumigation, and repeated under-dosing is how phosphine resistance develops.