Comparison of three methods of weight loss determination on maize stored in two farmer environments under natural infestation

Common methods of weight loss assessment in stored grain include the standard volume weight (SVW), count and weigh (C&W), the thousand grain mass (TGM) and the indirect with a conversion factor (CF) which have been used in varying storage environments. Apart from accuracy and reliability, practical application may limit their use in rural areas. Three of the methods: (SVW) or Bulk density (BD), C&W and CF were evaluated on maize stored in two farmer environments exposed to natural infestation. Baseline damage parameters: bulk density, grain moisture, sieved dust, weevil damage and insect pests per kilogram were established and again after 24 weeks. Weight loss was calculated using Equations 1 to 3. Percent weight loss varied by wide margins between treated and untreated maize: 4.4 to 12.3% (in Crib) and 0.3 to 9.9% (in house) for BD; 2.3 to 5% (in Crib) and 2.2 to 13.4% (in house) for C&W and 2.5 to 6.6% (in Crib) and 2 to 7% (in house) for the CF method. Generally, the house environment favoured pest establishment resulting to higher sample and cumulative weight loss in untreated maize. All the three methods had closely related weight loss figures in the same storage environment suggesting the need for careful selection of the preferred method based on practical application. C&W and CF provided the lowest results for the crib storage, but the ease in BD made it the preferred method in both environments.