Filing obligation for coffee growers limited when deemed business income is subject to reduced taxable portions, relieving small growers. Clarification that income from sale of coffee grown and cured by an individual is treated as deemed business income with a reduced taxable portion; individuals not covered by the first proviso need not file returns if their receipts from growing and curing coffee fall at or below the relief threshold corresponding to the lower taxable portion, and individuals engaged in growing, curing plus roasting and grinding need not file returns if their receipts fall at or below the lower threshold corresponding to the higher taxable portion.