Use by Asian Farmers of Soil Testing Services
Most Asian governments operate a national soil testing service. How does it benefit farmers, and how farmers make better use of it?
Role of Soil Testing
In the early years of national soil testing programs, the main aim was to identify any nutrient deficiencies of the soil. This is still a very important function. However, in some industrialized countries such as Japan and Korea, farmers have been applying large amounts of fertilizer for several decades. The soil nutrient status is already high. The main aim of soil testing in this situation is sustainable agriculture.
The Cost of Soil Testing
The cost of soil testing is high in relation to the average incomes of Asian farms. Some industrialized countries can afford to provide a subsidized testing service which farmers can use free of charge. Most other countries do not try to provide a free testing service for individual farmers. Instead, they do tests of major soil series and carry out field trials, to develop standard fertilizer recommendations.
Standard fertilizer recommendations can sometimes be tailored for individual use by computers and suitable software. In Malaysia, an expert system known as FERTO (Fertilizer Recommendation Tool) has been developed for high-yielding rice production. Korea has developed an on-line computerized database which combines information about land use, soil types and fertilizer recommendations. Use of the database is free of charge. You can visit it at
http://asis.rda.go.kr (in Korean only).
In Asian countries, a national soil testing service usually begins with fertilizer management for rice. Later, other crops are added, such as important fruits and vegetables.
Soil Testing for Fruit Crops
Fruit production is becoming increasingly important in many countries in Asia. Good harvests of fruit depend on good fertilizer management. Since fruit trees are perennial crops, their performance in any one year is partly determined by the amount of fertilizer they received in previous years. The higher the yield in any one year, the more nutrients are needed in the following year. Trees also need more fertilizer as they grow in age and size.
A common problem is that growers apply too much nitrogen fertilizer at the expense of other nutrients. Too much nitrogen may induce the growth of too many shoots and leaves, which shade the trees and reduce flowering and fruit set. Overuse of nitrogen may also mean that the harvested fruit has a lower sugar content.
Soil Testing to Improve Crop Quality
In the arly days of soil testing services, the main aim was to ensure that farmers applied enough fertilizer so the crop had all the nutrients it needed. This is still the main purpose in some Asian countries, but in others, the main aim of soil testing today is to make sure farmers don't apply too much fertilizer.
However, there is a problem in defining how much fertilizer is "too much". Fertilizer applications which are environmentally friendly are lower than those which give the maximum yield. How can farmers be compensated for this? One way is to adjust the price, to take the fertilizer management into account.
For example in fruit crops, the higher the nitrogen content of the leaf, the lower the sugar content (Brix) of the fruit. In Japan, the labelling and pricing of agricultural products, especially vegetables and fruits, is beginning to reflect the method of production, and the quality and flavor of the harvest.
When livestock manure is composted, its smell changes. Raw manure has a rancid odor, caused mainly by fatty acids. Composting changes this rancid odor to a pungent one. At an early stage of the composting process, the volatile fatty acids are broken down. However as composting proceeds, ammonia (NH3) and sulfur compounds are emitted in large quantities. It is this ammonia and sulfur which are considered to be the main cause of odor problems. Furthermore, the emission of large amounts of ammonia reduces the level of nitrogen in the finished compost, so it has less value as a fertilizer for crops.
Soil Testing for Micronutrients
If soil testing detects a nutrient deficiency, the problem can be solved by applying a small amount (e.g. 20-30 kg/ha) of chemical fertilizer which contains the element needed. However, soil testing for a range of micronutrients is expensive. A cheaper solution may be to apply an organic fertilizer such as composted chicken manure.
Organic fertilizer not only improves the soil physical properties, but supplies a range of micronutrients. While each of these is needed by the crop only in tiny amounts, the absence of any one of them may have a very damaging effect on crop performance.
Soil Testing to Improve Crop Quality
In the arly days of soil testing services, the main aim was to ensure that farmers applied enough fertilizer so the crop had all the nutrients it needed. This is still the main purpose in some Asian countries, but in others, the main aim of soil testing today is to make sure farmers don't apply too much fertilizer.
However, there is a problem in defining how much fertilizer is "too much". Fertilizer applications which are environmentally friendly are lower than those which give the maximum yield. How can farmers be compensated for this? One way is to adjust the price, to take the fertilizer management into account.
For example in fruit crops, the higher the nitrogen content of the leaf, the lower the sugar content (Brix) of the fruit. In Japan, the labelling and pricing of agricultural products, especially vegetables and fruits, is beginning to reflect the method of production, and the quality and flavor of the harvest.
When livestock manure is composted, its smell changes. Raw manure has a rancid odor, caused mainly by fatty acids. Composting changes this rancid odor to a pungent one. At an early stage of the composting process, the volatile fatty acids are broken down. However as composting proceeds, ammonia (NH3) and sulfur compounds are emitted in large quantities. It is this ammonia and sulfur which are considered to be the main cause of odor problems. Furthermore, the emission of large amounts of ammonia reduces the level of nitrogen in the finished compost, so it has less value as a fertilizer for crops.
The DR. Soils Program
An innovative program in Thailand uses mobile soil testing vans which visit rural villages. The vans analyze soil samples brought in by farmers, and make fertilizer recommendations. The program is run by the Department of Land Development (DLD).
The "Dr. Soils" are farmers selected from each village who are trained in basic soil testing and land development techniques. The program has been operating for ten years. There are now 63,000 Dr. Soils from 67,000 villages. Dr. Soils are volunteers, who are not paid a salary but are given a distinctive yellow jacket. The DLD also gives them a small farm pond.
Dr. Soils help DLD staff to train farmers how to take soil samples. This is very important. If soil samples are not taken properly, all subsequent analysis is useless. On the day when the van is scheduled to visit their village, farmers take their samples to a central place such as the village temple or school.
They hand in their samples in the morning, and get the results in the afternoon. While farmers are waiting for their samples to be analyzed, the DLD staff take the opportunity to educate farmers about the features and management of local soil types, and proper fertilizer use.
Index of Images
Figure 1 Young Durian Trees Growing in Raised Beds in a Paddy Field, Vietnam. Durian Trees Give a Good Income but Take a Long Time to Mature. in This Way, the Grower Can Get an Income from Rice While He Converts His Paddy Field into a Durian Orchard
Figure 2 A "DR. Soils" Mobile Soil Testing Laboratory, Thailand
Figure 3 Label for Home Delivery of Tomato, Japan. the Label Shows the Brix of the Crop.
Figure 4 Muskmelon with Magnesium Deficiency in Korean Greenhouse
Figure 5 Normal Muskmelon
