Indigo green manuring technology: socioeconomic and technical dimensions

Green manuring involves the incorporation into the soil of any field crop while green (fresh and relatively young) for the purpose of soil improvement. Among the good green manure crops is indigo (Indigofera tinctoria L.) It produces large amounts of biomass ranging from 2.19 to 2.57 t/ha in 210 days, which contributes 38-71 kg N/ha.

Indigo green manuring is a century-old indigenous practice that dates back to the late 19th century. The indigo is planted in time with the schedule of irrigation of the dry season crop and the indigo biomass is incorporated in the soil simultaneously with the land preparation for the wet season rice crop. This farming practice can be observed today in five provinces of northwestern Luzon, namely: Ilocos Norte, Ilocos Sur, Abra, La Union and Pangasinan. However, its social acceptability by the present generation farmers is in question. Hence, Agustin and co-workers (MMSU, PHILRICE and IRRI) conducted a survey of indigo users and non-users in Bado, Ilocos Norte to determine the technical and social factors that explain the low adoption of indigo as green manure crop. In addition to the survey, an on-farm trial was conducted to demonstrate the effects of indigo green manuring on rice yield and prove the economic viability of the technology.

Findings

• The survey gave the following information:

  - Most indigo users were older than the non-users. Indigo users had an average age of 62 while the non-users’ average age was 53. This points to older farmers being familiar with the technology and they could have appreciated the benefits from the technology.
  - None of the indigo users was a pure tenant. Of the 15 indigo users, 33% were farm owners, 53% were owner-tenants and 14% were either owner-leasee or owner-tenant-leasee. Of the 19 non-users, 29% were farm-owners, 21% were pure tenants and 53% were owner-tenants. These suggests that lack of land tenure security deter farmers from undertaking soil protection measures.
  - All respondents practiced rice-based cropping system, i.e., rice during the wet season followed by dry season cash crops, such as onion, garlic, peanut, mungbean and corn.
  - Indigo users usually devoted half of their farms, or an average of 0.56 ha, to indigo green manuring. However, the use of indigo was dictated by the availability of water and indigo planting materials.
  - Indigo users cited both positive and negative feedbacks from applying indigo green manuring. The positive feedbacks included the following: it enhanced soil fertility; improved soil tilth; reduced the amount of chemical fertilizer input; and increased rice grain yield. The negative feedbacks were: suppression or injury or death of the newly transplanted seedlings; weed growth; and difficulty in land preparation.
  - The non-users cited the following reasons for non-adoption: limited supply and high cost of indigo seeds; difficulty in land preparation and transplanting; limited water supply; availability of chemical fertilizers; and lack of farm machinery for green manure incorporation.

• The on-farm trial showed that rice grain yields in the indigo green manure plots (5,444 kg/ha) were significantly higher than those in plots without indigo (4,197 kg/ha).
• The cost-and-return analysis of the wet-season rice crop showed that the indigo green manure technology was more profitable, giving a net income of P21,845.60/ha, as compared with the non-indigo farmers’ practice, which gave P8,538.60/ha. The increase in rice yields and savings from the reduction in the use of chemical fertilizers have contributed to the increase in net income.

Source: PCARRD, 2001. Highlights 2000, Los Banos, Laguna.

Organic Farming Information Network
Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD)
©2006