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7.5 Sloping Agricultural Land Technology (SALT) in the Philippines

W.A. Laquihon and M.V. Pagbilao


Introduction
Historical Background
The Extension of SALT Nationwide
Soil Erosion Control
Crop Productivity
Labour Management
Conclusions
References


Introduction

The strategy of using tree legumes to improve the fertility and stability of agricultural soils is receiving increased attention in developing countries. It provides a means for resource-poor farmers to achieve sustainable production without the use of expensive, and often unavailable, chemical fertilisers.

In the southern part of the Philippines, the Mindanao Baptist Rural Life Center (MBRLC), a non-government organisation based in Kinuskusan, Bansalan, Davao del Sur, has developed a conservation farming scheme called Sloping Agricultural Land Technology (SALT), based on the use of tree and shrub legumes.

SALT is a simple, applicable, low-cost method of upland farming. It is a scheme developed for small farmers with few tools, little capital and little knowledge of modern agriculture.

SALT is a form of alley farming in which field and perennial crops are grown in bands 4-5 m wide between contoured rows of leguminous trees and shrubs. The latter are thickly planted in double rows to form hedgerows.

When the hedge reaches 1.5-2.0 m in height, it is cut back to 40 cm and the cuttings are placed in the alleys between the hedgerows to serve as mulch and organic fertiliser or green manure.

The species used in the hedgerows include Leucaena leucocephala, L. diversifolia, Calliandra calothyrsus, Gliricidia sepium, Flemingia macrophylla and Desmodium rensonii. Farmers are encouraged to use a combination of these species or other fast-growing, fast-coppicing and high-biomass leguminous trees or shrubs found to be suitable on their respective farms. Presently, the MBRLC is testing the performance of over 20 species of shrub and tree legumes for hedgerow and forage use.

Rows of perennial crops such as coffee, cacao, citrus and banana are planted on every third alley created by contoured hedgerows. The alleys not occupied by permanent crops are planted alternately to cereals (e.g. com, upland rice or sorghum) or other crops (e.g. sweet potato, melon or pineapple) and legumes (e.g. mungbean, string bean, soybean or peanut). This cyclical cropping provides the farmer with several harvests throughout the year. The average monthly income to one family from 1 ha of SALT farm is approximately P1,300 (1 US$ = P25).

On a SALT farm, a farmer can grow varieties of crops familiar to him. SALT can be adapted to incorporate new or traditional farming techniques. If farmers leave the land fallow for one or two cropping cycles, the leguminous trees and shrubs will continue to grow and may be harvested later for firewood and charcoal (Tacio 1991).

Historical Background

In the early 1970s, MBRLC staff members heard numerous complaints of low and declining farm income from upland farmers in Kinuskusan, Bansalan, Davao del Sur. In one area, corn production had declined from 3.5 to about 0.5 t/ha in a span of 10 years. Yields of other crops had also declined to unprofitable levels during the same period. It was found that the main reason for these low yields was depletion of soil and nutrients through erosion.

At first, the Center tried many standard ways to stop erosion and rebuild soil fertility. Nothing worked. Then, MBRLC obtained seeds of Leucaena leucocephala from the Nitrogen Fixing Tree Association (NFTA) in Hawaii. Double hedges of Leucaena leucocephala were planted on contours 4-5 m apart and crops and fruit trees were grown between the hedges.

This technique appeared to be successful. Soil erosion was minimised, soil fertility restored, crop yields were sustained and improved income for upland families was generated. Because of SALT's initial success, three more SALT variants have been developed. These are Simple Agro-Livestock Technology (SALT-2), Sustainable Agroforestry Land Technology (SALT-3) and Small Agro-fruit Livelihood Technology (SALT-4).

SALT-2 is a goat-based agroforestry project with a land use comprising 40% agriculture, 20% forestry and 40% livestock. SALT-3 is a small-scale reforestation technology with 40% of farm area devoted to agriculture and 60% to forestry (Figure 7.5.1). SALT-4 is a system of planting fruit trees and short-term crops at a ratio of 75%:25%. All of these variants utilise shrub and tree legumes in contour hedgerows.

The Extension of SALT Nationwide

Many public and private organisations in the Philippines believe in the potential of SALT for upland development (Table 7.5.1). These organisations have voluntarily disseminated the technology to their clientele. SALT farms, established with the help of these organisations, now occupy over 5,000 ha throughout the country.

Fig. 7.5.1. Sustainable Agroforestry Land Technology (SALT-3).

Table 7.5.1. List of organisations using SALT since 1981, and the estimated number of cooperators.

Adopting organisation

Category*

Year

Estimated no. of cooperators

Federation of Free Farmers

NGO

1981

15

US Peace Corps Volunteer

NGO

1981

30

Forest Management Bureaua

GO

1981

15

Southern Philippines Dev. Authority

GO

1982

15

Kilusang Kabuhayan at Kaunlaranb

GO

1982

100

Phil.-Australian Dev. Assistance Program

GO

1982

700

Department of Agrarian Reform

GO

1982

10

British Volunteers

NGO

1982

10

Agric. Education Outreach Projectc

GO

1983

150

Farm Systems Dev. Corporation

GO

1983

30

Davao Medical School Foundation

NGO

1983

20

Farmers Training Center for Rural Development

GO

1984

50

Department of Agriculture

GO

1984

500

Overseas Missionary Fellowship

NGO

1984

20

National Electrification Administration

GO

1985

503

Save the Children Foundation

NGO

1985

25

Support Technology Assisting Rural Transmigration

NGO

1985

10

Cotabato Rural Upliftment Movement

NGO

1985

15

International Human Assistance Program

NGO

1985

15

Catholic Santa Cruz Mission

NGO

1985

50

Regional Rainfed Development Program

GO

1985

30

Philippines Business for Social Progress

NGO

1986

50

Resources Ecology Foundation for Regeneration of Mindanao, Inc.

NGO

1987

100

DAR-UNDP-FAO

GO

1988

150

Central Visayas Regional Project

GO

1988

50

Meralco Foundation, Inc.

NGO

1989

200

Kapwa Upliftment Foundation, Inc.

NGO

1989

30

Mag-Uugmad Foundation

NGO

1989

50

Muslim-Christian Agency for Rural Development Inc.

NGO

1989

15

Soil and Water Conservation Foundation

NGO

1991

150

* NGO = non-government organisation
GO = government organisation
a Then known as Bureau of Forest Development
b This was under the Ministry of Human Settlements
c In collaboration with the United States Agency for International Development (USAID) and the Ministry of Education, Culture and Sports

The Department of Agriculture used SALT as the basis for its extension effort on sloping uplands. The Department of Environment and Natural Resources endorsed the concept for its social forestry pilot projects. A significant training effort for extension personnel was launched by the Philippine Government and demonstration plots of SALT were installed on farmers' fields throughout the country.

Soil Erosion Control

To verify the effectiveness of the SALT system for controlling soil erosion, an experiment was established in 1984 to compare the SALT system with a non-SALT system used by local farmers. There were two replications of each system with individual plots measuring 800 m2.

Soil losses in both systems were assessed using a staking method which measured changes in soil levels throughout the plots. This method was found to be relatively inaccurate and tended to overestimate erosion in the SALT treatment. A correction factor (E. Paningbatan and S.A. El-Swaify, personal communication) was applied to all measurements and the final results of the study are presented in Table 7.5.2.

Table 7.5.2. Soil losses In SALT* compared with non-SALT systems.

Months from start of test

SALT. (mm)

Non-SALT (mm)

SALT. (t/ha)

Non-SALT (t/ha)

0

0.0

0.0

0.0

0.0

5

0.5

4.0

6.2

53.8

34

0.8

20.9

10.6

278.0

45

1.2

46.5

15.6

618.1

50

1.6

58.4

21.3

776.2

57

1.7

71.4

22.0

950.1

60

1.7

77.1

23.1

1025.4

68

1.6

82.8

21.4

1101.1

72

1.5

87.4

20.2

1162.4

Mean loss/year

0.25

14.6

3.4

194.3

* SALT soil loss calculated with a correction factor

The SALT system was very effective in controlling soil erosion as there was almost 58 times less erosion in the SALT system than in the non-SALT treatment.

The annual rate of soil loss from the SALT system was 3.4 t/ha which is well within the tolerable limits for soil loss. Palmer (1991) suggested that acceptable soil loss limits for the tropics were within the range 10-12 t/ha/year.

Crop Productivity

MBRLC has also conducted tests on crop productivity with emphasis on corn, a traditional upland crop in the Philippines, particularly in Mindanao. The influence of leucaena mulch on corn yields and the effect of minimum inputs of inorganic fertiliser on productivity were of interest to MBRLC.

One trial studied the effect of organic and inorganic nitrogen sources (leucaena mulch and fertiliser) on DMR-2 corn production over eight croppings. There was a significant increase in corn yields when either leucaena or fertiliser was used with the fertiliser being more effective than leucaena (Table 7.5.3). However, the leucaena mulch treatment produced double the yield of the no-fertiliser plots. Fertiliser treatments increased yield three-fold.

Table 7.5.3 Effect of nitrogen sources on DMR-2 corn production over eight croppings.

Treatment

Corn yield (t/ha)

No fertiliser

1.3

Leucaena mulch from hedgerow*

2.7

Fertiliser** + leucaena mulch

3.7

Leucaena mulch = fertiliser

2.6

Fertiliser only*

3.7

LSD 5%

0.7

* 8.7 t dry matter/ha/year
** 100 kg N. so kg P/ha

Another trial was conducted to determine if continuous corn production on the same piece of land (using leucaena mulch as fertiliser) would eventually deplete the soil of nutrients. Results revealed that after ten continuous crops of corn over a period of 39 months, the yield was slightly lower than at the start but significantly higher than the national average. This indicated that leucaena mulch can sustain reasonable yields of corn over time.

A ten-year economic study (1981-1990) conducted at the MBRLC farm showed that a 1 ha SALT area can increase an upland farmer's income substantially. The average net annual income for upland farmers in the Bansalan area was about P4,000 (US$1 = P25) with most farmers tilling more than 1 ha of land. After adopting SALT, farmers' net incomes increased from P4,595 to P15,981 ha/year.

Labour Management

Based on observations of the first few years of implementation of SALT, MBRLC staff estimated that management of 1 ha of SALT required much more labour than management of a 1 ha farm planted to corn.

MBRLC's observations were based upon the relatively high amount of labour required to establish a SALT project (locating contour lines, seedbed preparation, planting the leguminous trees and shrubs, trimming the hedgerows, etc.). However, further studies showed that when averaged over a longer period of time, 1 ha of SALT may involve less labour input than 1 ha of corn under the traditional management system.

Several factors contributed to the decrease of labour requirements in SALT with time. Firstly, there was a build-up of rich organic mulch from the trimmings of the hedgerows. This helped in control of weed growth and reduced labour requirement for weeding. Also, as the permanent crops on the SALT farm became established, there was less area for planting, harvesting and caring for annual crops. This reduced labour input as less labour was required for permanent perennial crops than for seasonal crops such as corn.

A cost and return analysis for 5 years for the Simple Agro-Livestock Technology (SALT-2) showed that the system generated a monthly net profit of P5,320/ha, which was 7-8 times higher than the traditional method of upland farming. In addition to this financial benefit, the farming family became more self-sufficient growing a wider range of food crops and producing approximately 4,700 litres of goat's milk per year for sale or consumption. The soil was protected and fertilised with up to 16 t of goat manure per year thus further enhancing productivity and sustainability.

The small-scale, long-term, 2 ha reforestation model called Sustainable Agroforest Land Technology (SALT-3), in its fifth year realised a net profit of P2,393.33 per month. The return on investment was 42%. Like the first two SALT schemes, SALT-3 controlled soil erosion and provided food, fuelwood and timber to the farmers.

Conclusions

Despite the many benefits of this shrub and tree legume-based alley farming system (e.g. soil protection and amelioration, landscape stability, sustained production and economic benefits), there are still many upland farmers in the Philippines who are not adopting the SALT scheme. Thus, Watson and Laquihon (1985) stressed:

'There is not and never will be one system for all farmers. SALT is not a miracle system or a panacea To establish a one-hectare SALT farm requires much hard work and discipline. It took many years to deplete the soil of nutrients and lose the topsoil; no system can bring depleted, eroded soils back into production in a few short years. The price of soil loss is poverty, but we have seen land restored to a reasonable level of productivity by using SALT.'

References

Palmer, J.J. (1991) The Sloping Agricultural Land Technology (SALT) Experience. Paper presented at The Sloping Agricultural Land Technology (SALT) Workshop, Xavier Institute of Management, Bhubaneswar, Orissa India

Tacio, H.D. (1991) Save the topsoil from erosion. The PCARRD Monitor, 19, No. 5, September-October 1991. Philippine Council for Agricultural Resources Research and Development, Los Banos, Philippines.

Watson, H.R. and Laquihon, W.A. (1985) Sloping Agricultural Land Technology (SALT) as developed by the Mindanao Baptist Rural Life Center. Paper presented at the Workshop on Site Protection and Amelioration, Institute of Forest Conservation of the University of the Philippines, Los Banos, Philippines.


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