Scientists in Bukidnon recently discovered that crop wastes from cabbage, cauliflower and other cruciferous vegetables mixed with the soil can effectively control soil-borne diseases such as bacterial wilt and root knot, which affect potato plants.

According to the Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD), the approach of using crop wastes from crucifers – plants with four-petaled flowers and long, narrow seed pods – is anchored on the concept of biofumigation.

“Biofumigation is a process by which soil-borne pests and pathogens are suppressed by naturally-occurring biocidal compounds called isothiocyanates,” PCARRD said, adding that the ITCs “are released into the soil when the tissues of crucifers such as brocolli, radish, cauliflower, (and) cabbage” decompose.

PCARRD said bacterial wilt caused by soil bacterium Ralstonia solanacearum and root knot caused by nematodes are “major constraints” in potato production.

“In Benguet, Bukidnon and Davao del Sur, bacterial wilt infection can reach up to 90 percent, while root knot accounts for 25 to 50 percent yield loss in many crops, including potato,” PCCARD said.

Following a PCARRD survey, which found that 60 to 80 percent of crucifer stems and leaves are left in the field after harvest in Bukidnon, Abragan’s team sought to evaluate the potential of these crop wastes as biofumigants against bacterial wilt and root knot.

They gathered and shredded the leaves, stems and roots of crucifers left over from the previous harvest, then mixed the shredded plants into the soil at a ratio of five kilos per square meter.

Abragan’s team found out that when a mix of different crucifers is incorporated into the soil, the incidence of bacterial wilt could be as low as 21 percent and the potato crop yield as high as 11 tons per hectare.

The incidence of bacterial wilt in untreated soil could be as high as 58 percent, and potato crop yield as low as six tons per hectare.

The results of farm trials in Lantapan, Bukidnon showed the use of mixed crucifers as biofumigants resulted in yields of eight to 11 tons per hectare, a net income between P198,000 and P286,000 and a return on investment (ROI) of 133 to 193 percent.

Without biofumigation, Abragan’s team found that the yield was at 6.67 tons per hectare, net income at P166,750 and the ROI was at only 114 percent.