Food and Fertilizer Technology Center - publications

Nov. 30, -0001

Plant and Soil Analysis As a Guide to Crop Fertilization


Need for Plant and Soil Testing in Asia


Although chemical fertilizers have brought great benefits to Asian agriculture, they have also brought a number of problems which are tending to become more serious over the years. Overuse of fertilizer is a problem in many industrialized countries in Asia, particularly with regard to nitrates and phosphates. Some studies have suggested that between a fifth and a half of the chemical fertilizer being applied by farmers is unnecessary.


Not only is fertilizer overuse wasteful, but it can result in the contamination of both crops and water resources with nitrates and other residues. Furthermore, quite apart from the pollution problems, overuse of fertilizers means higher costs for farmers and wasted resources.


Soil testing and plant diagnosis make it possible for farmers to assess the nutrient status of the soil and crop, and apply fertilizers only when there is a deficiency to be corrected. This solves the problem of overuse, and means that crops benefit from a balanced fertilizer regime. In countries where fertilizer applications are very low because of economic constraints, soil and plant testing can help farmers improve the timing and quantity of their fertilizer applications, to make sure that they bring the maximum benefit in terms of crop yield.


WHY Test Both the Soil and Plant Tissue?


Soil testing and leaf diagnosis are complementary. Soil testing has the advantage of being able to measure the level of nutrients available in the soil, and the extent to which these will be available to the crop during the growing period. Leaf diagnosis shows the nutrient status of the plant at the particular time of sampling, often in time for any deficiencies to be remedied while the crop is still growing to maturity.


However, leaf diagnosis alone may not give an accurate picture of fertilizer requirements. Soil nutrient levels are only one of many factors which determine a crop's nutritional status. There are other important factors which influence nutrient uptake by plants, such as temperature, and various stresses such as water deficiency or water surplus. Furthermore, the presence or absence of one nutrient element may affect the uptake of another. Because of the complexity of factors affecting the results, leaf analysis has to be integrated with soil analysis.


Regional Use of Soil Testing and Plant Analysis


Most countries in Asia carry out soil testing and leaf analysis in various private and government laboratories. Taiwan has a single centralized laboratory for all soil and leaf diagnosis tests for farmers, in order to have standardized procedures and results. This is operated by the Taiwan Agricultural Research Institute. Other countries such as Japan and Korea have numerous provincial or prefectural laboratories operated by the government. In others, such as Thailand, there are both private and government testing laboratories, and farmers ordinarily pay a fee for soil testing.


In the small-scale farms typical of most of Asia, it is difficult to provide a comprehensive testing service for large numbers of small farms. For the most part, soil testing is not used to make fertilizer recommendations for individual smallholders. Soils are grouped into major soil series, and general recommendations are made according to the particular soil and crop type.


Malaysia has developed a highly successful leaf testing program for plantation crops. These are perennial crops which benefit greatly from a long-term program which provides an efficient fertilizer budget designed to maximize long-term productivity, while at the same time keeping a check on any build-up of fertilizer in the soil. Since yields are often very high - more than 25 mt/ha/year of fresh fruit bunches from oil palm, for example - a large amount of fertilizer is needed to compensate for the nutrients lost when the crop is harvested. More than 50 field trials for oil palm have been carried on various soils of Peninsular Malaysia to test leaf nutrient levels in relation to maximum yield.


Similar testing has been carried out for other cash crops. Since the results of leaf testing vary according to the age of the leaf, its position on the tree etc., testing procedures in Malaysia have been standardized. For example in leaf diagnosis for oil palm, the central leaflets of frond 17 are usually selected, while in the case of coconut it is leaf 14 which is used. A computer program has been developed for oil palm which, given a particular soil type and the results of the leaf test, can predict the probable yield. If there seems to be any nutrient deficiency, the program can recommend fertilizer applications to give the maximum yield. The Palm Oil Research Institute which developed the program is meanwhile continuing to carry out fertilizer trials to monitor the results of fertilizer applications, and compare predicted yields based on soil type and leaf diagnosis with actual ones.


Although this type of program is very useful, the model can only be applied to parts of Malaysia which have the same soil types as the sites tested, and where similar crop varieties or lines are being grown. One common problem in both soil testing and leaf diagnosis in the region is the lack of field trials on the correlation between soil or leaf tests results, and crop response to fertilizer.


Information about a particular level of K or P in the leaf or the soil means little in itself. It must be related to field tests which show how this information is related to the nutrient status of the crop, the presence of any nutrient deficiency, and the response of the crop to various levels of applied fertilizer. Obtaining this calibrated empirical data is a laborious process, since it must be repeated over several years to allow for seasonal variations, and be carried out separately for different crops as well as for different soil types (and sometimes for other factors as well, such as the presence or absence of irrigation).


Not only agronomic data, but also economic data on fertilizer costs and prices for agricultural products, must be taken into account when fertilizer recommendations are being made. One paper presented at the Workshop described the situation in Thailand, where chemical fertilizer is imported and expensive. The completion of the National Fertilizer Factory within the next few years is expected to reduce fertilizer costs considerably. At present, although Thailand is a major exporter of agricultural products, the rate of fertilizer application is very low compared to many other countries in the region. Most agriculture in Thailand is rainfed, which inevitably means some risk of crop failure from water deficiency. Field tests of the yield, fertilizer rate, costs and profits for corn in Thailand showed that nitrogen fertilizer use was profitable only on Mollisols (clay), while on Ultisols (sandy soils) it gave a marginal or negative return. No benefits were seen from the application of P and K, which in fact reduced yields if these were applied without any N fertilizer. In general, chemical fertilizer gave the best returns when applied to high-value crops in irrigated areas.


Cross Checking of Soil Samples


To ensure uniformity, there is a need for standard samples and cross checking of results from different laboratories. The system of cross checking used in Malaysia since 1971 might serve as a model. Participation is on a voluntary basis, and there are now about 30 laboratories participating in the scheme, which is supervised by a committee. Standard samples are sent out every four months to be analyzed, and the committee compares the results from different laboratories. If there are discrepancies, the laboratory in question is asked to identify the problem and report to the committee.


Problems in Nitrogen Testing


The analysis of soil samples is technically more difficult than leaf analysis, and presents a number of problems. Testing for soil nitrogen is particularly difficult, since the results can be affected by soil moisture, temperature, and many other factors. As a result, there is often little or no correlation between the level of nitrogen in the test results and the crop yield. However, testing the level of soil N can be useful in other ways.


In the multiple cropping systems common in Taiwan, N testing after harvest of the first crop can indicate how much residual N is left for the second crop. Testing of the soil N level shortly before planting can also be a valuable guide to fertilizer requirements for the young plant. In the case of corn, which responds well to side dressings of N, a soil sample from a depth of 30 cm can indicate whether enough N is available. If there is not, an application of N soon after testing can give good results.


Effect of Soil and Plant Testing on Farm Practices


New laboratory equipment has improved the accuracy and speed of analysis. While these are great advantages, we also need to keep the cost of testing down, especially for low-income farmers. Although soil scientists have been devoting much effort to soil and plant testing methods, they should perhaps consider the effectiveness of these methods in improving actual farm practices. In spite of the analysis of numerous soil samples, farmers in Taiwan, for example, are still applying excessive amounts of fertilizer. Soil scientists might go on to study this excessive use of fertilizer and develop programs to reduce it.


In some countries, there is only a limited range of fertilizers available. Although soil and plant testing might give a sophisticated picture of crop nutrient requirements, farmers are unable to fulfill these if only a single fertilizer grade is available. Perhaps soil scientists should not limit themselves to diagnostic procedures, but should work with policy makers to help ensure that proper fertilizers are readily available.


FFTC International Workshop


Leaf Diagnosis and Soil Testing As a Guide to Crop Fertilization




Location: Taiwan ROC

Date: September 12-17 1994

No. Participating Countries: 8 (Indonesia, Japan, Korea, Malaysia, Philippines,Republic of China, Thailand, Western Samoa)No. Papers: 17

No. Participants: 19 plus observers

Co-sponsors: Council of Agriculture, ROCTaiwan Agricultural Research Institute


List of Papers


Keynote Speech: Recent developments in leaf diagnosis and soil testing as a guide to crop fertilizatio

n- Masayoshi Koshino

1. Research on leaf diagnosis criteria and its application on fertilizer recommendation for citrus orchards in Taiwa

- Su-San Chang

2. Establishment of critical nutrient levels of N, P and K in the soil and in the leaf for Catimor coffee

- Renato Alazada Apolinares

3. The use of plant analysis to assess nutrient status and fertilizer recommendation especially for perennial crops

- Justina Sri Adiningsih Soejitno

4. Use of foliar and soil analysis in determining nutrient requirements of rubber (Hevea brasiliensis) in Malaysia

- Aminuddin Hussin

5. The assessment of soil nitrogen availability in sugarcane field by hot water extraction

- Song-Wu Li

6. Making criteria of soil diagnosis for the fertilizer recommendation to upland crops

- Beom-Lyang Huh

7. Search for fertilizer recommendation to rice production in Thailand

- Pornpimol Chaiwanakupt

8. The development of soil testing program for food crop fertilizer recommendation in Indonesia

- I.P.G. Widjaja-Adhi

9. Outbreak mechanisms of aphanomyces root rot in spinach and its control based on nitrogen-fertilizer management

- Kazutaka Akashi

10. Control of potato scab by exchangeable aluminum in soil

- Naoharu Mizuno

11. Nutrient uptake as affected by rootzone environment in hydroponically grown vegetables

- Byoung-Choon Jang

12. Soil testing as a basis for fertilizer recommendation on peanut grown in lahar deposits

- Nenita Esteban Dela Cruz

13. Diagnostic recommendation integrated system (DRIS) approach to predict nutrient balances in the leaf and in the soil for banana

- Modesto R. Recel

14. Fertilizer recommendation for economic field crops in Thailand

- Tasnee Attanandana

15. Successful examples of diagnosing fertilizer requirements in Western Samoa

- Loku Gamage Gnanapala Yapa

16. Fertilizer recommendation system for oil palm in Peninsular Malaysia

- Zin Zawawi Zakaria

17. Use of plant analysis and soil testing for plantation crop

- Elinthamby Pushparajah


List of Papers



Keynote Speech
: Recent developments in leaf diagnosis and soil testing as a guide to crop fertilization


- Masayoshi Koshino


1. Research on leaf diagnosis criteria and its application on fertilizer recommendation for citrus orchards in Taiwan


- Su-San Chang


2. Establishment of critical nutrient levels of N, P and K in the soil and in the leaf for Catimor coffee


- Renato Alazada Apolinares


3. The use of plant analysis to assess nutrient status and fertilizer recommendation especially for perennial crops


- Justina Sri Adiningsih Soejitno



4. Use of foliar and soil analysis in determining nutrient requirements of rubber
(Hevea brasiliensis)
in Malaysia


Index of Images


Figure 1 Young Plant of Kiwi Fruit with Magnesium Deficiency


Figure 1 Young Plant of Kiwi Fruit with Magnesium Deficiency


Figure 2 Jujube with Iron Deficiency


Figure 2 Jujube with Iron Deficiency


Figure 3 Papaya Roots with Symptoms of Phosphorus Deficiency (Normal Whitish Roots on Left)


Figure 3 Papaya Roots with Symptoms of Phosphorus Deficiency (Normal Whitish Roots on Left)

Read more

VIEW ALL
FFTC 2017 ANNUAL REPORT
FFTC 2016 ANNUAL REPORT
2015 ANNUAL REPORT
Postharvest Losses of Fruit and Vegetables in Asia
Postharvest Losses of Fruit and Vegetables in Asia
AgriculturalPolicy DragonFruitNetwork
loading