Soil Info
On the agricultural extension
on fertilizer - soil improvement

Dr. Tran Khai
President of Vietnam Soil Science Society



 

1. Current status of soil
           In recent years in agriculture many useful agricultural extension activities have been carried out on crops, animals, use of new varieties and integrated pest management (IPM)... However, there are hardly any agricultural extension activities  on fertilizer - soil improvement . > any people find this fact wuite worrying because it is not suitable to the setting of a country with  limited land resource and not high quality of soils. The average per capita area of natural land as well as arable land is very low and Vietnam can be included in the group of countries with lowest land area per capita, moreover, the area of bare land and denuded hills, degraded soils, "problem" soils occupies more than 50% of land area of the country. Statistical survey data show that:
                    - bare land and denuded hills occupy 11 million ha, in which 4.8 million ha are with thin soil thickness.
                    - Degraded gray soils: 2.5 million ha.
                    - Sandy soils: 0.5 million ha.
                    - Acid sulphate soils: 1.8 million ha.
                    - Coastal saline soils: 0.97 million ha.
                    - Gleyey and partially - waterlogged soils: 0.45 million ha.
           With a rather high population growth rate as that at present, the population of Vietnam will soon reach 100 million people . If the soil quality and soil use structure are not improved, it will be difficult to ensure the safety of food self-sufficiency, needless to mention the difficulty in maintaining exportation at present level.
    The above mentioned status urges us to pay more attention to the agricultural extension on fertilizer soil improvement following the tradition of our people: Inch of land - inch of gold, water first -fertilizer second... going up from the SOIL and it is also the scientific approach recognized by the world.
2. Soil characteristics related to fertilizers - soil improvement.
           Soils, fertilizers and crops are in a production system and cannot   be separated so that high economic efficient can be obtained. therefore, it is necessary to thoroughly understand soil properties to seasonably apply fertilizers for crops, on contrary fertilization is also a measure of soil improvement to increase soil effective fertility. In soil classification, Vietnam has 14 soil groups and 31 soil units (soil map at scale of 1: 106), however, for easier evaluation these soils can be grouped into 3 big combinations:
2.1. Mountainous and hilly soils:
            Most of mountainous and hilly soils in our county are Acrisoils, Ferralsols, Alisols. Due to slope topography, after reclamation for annual production the soils surfer from leaching, erosion with large amount of soil loss, the soils can be degraded easily and suffer from loss of productivity. The organic matter, humus, nitrogen are weathered and rapidly decreased after 1-2 crops. CEC is low, the fertilizer retention capacity is low, alkaline and alkaline - earth cations decrease, base saturation drops below 50%, the soils become acid , more and more H+ and Al +++ appear, accumulation of sesqui-oxides increases. The fixed P2O5 is large. Without reasonable improving measures, the soil environment is rapidly degraded and it is the reason for shifting cultivation, bare land and denuded hills and desertification. The mountainous and hilly soils have to be reserved for afforestation, cultivation of industrial crops, fruit crops, perennial ash crops with measures of protecting the soils from leaching, erosion, controlled release fertilizer, physiologically alkaline fertilizers (fused magnesium phosphate...). We must find out all the ways of increasing soil organic matter such as application of organic fertilizers, cultivation of green manure plants, incorporation of green biomass, returning crop residues and agricultural by-products to the soil. For some crops which may be in lack of sulfur or micro nutrients, it is necessary to change the structure of chemical fertilizers or to use foliar fertilizers to apply to the crops at necessary stages.
2.2. Alluvial soils in the delta:
       The centers od food and foodstuff production in our country are mainly on large deltas such as the Red River delta, the Mekong River delta and deltas of other rivers. These are regions with high level of intensive cultivation and crop intensity. With irrigation, the soil moisture is sufficient, the rate of soil degradation is lower, in many places alluvial source is supplemented and organic and mineral fertilizers are used, the effective fertility of soils is thus maintained.
        However, at higher level of production, the soil use coefficient increases so as to have higher kneel total output, the existing measures of fertilization soil improvement has to be much more improved, it is necessary to apply sufficient fertilizer amount, balanced nutrients, more organic fertilizers and use widely rice straw incorporation, reasonable irrigation and drainae and appropriate wet-dry rotation (2 flooded rice crops - 1 dry - farming crop...) with larger area of legumes.
2.3. Soils with problems of fertility:
        Most of our provinces are with poor soils, degraded soils and soils with problems of fertility with larger or smaller areas. In these regions crop yields are low and life of people faces difficulties. The basis measures of soil improvement are required to overcome crop yield limiting factors and on this basis to apply a reasonable fertilization regime.
            - Degraded gray soils, sandy soils are the soils with light texture and poor in nutrient with low CEC, therefor applied fertilizers an easily be leached. Many research results show that after solving the irrigation problem, keeping soil moisture, strengthening the soil organic matter and clay content, the application of chemical fertilizers will give high efficiency and crop yield will not be lower than that in the other soil regions.
            - Saline soils, acid sulphate soils, swampy and waterlogged soils are usually with rather high potential fertility but many saline salts and toxic substances (H2S,  Al+++, Mn++, Fe++). It is necessary to solve the water problem for washing the soil acidity and salinity, limiting the sulphate acidity and salinity of apply the special land preparation measures such as terracing, ridging, mulching to fight against acidity and salinity formation, and use chemical fertilizers suitable for each soil type. Acid sulphate soils, swampy and waterlogged soils need phosphorus fertilizers, especially fused magnesium phosphate.
3. New concepts in agricultural production related to fertilizer use.
            Nowadays in the world there have been published many research results and models of agricultural production with high quality and economic efficiency with the common direction of developing an humane and sustainable agriculture such as organic agriculture, clean agriculture, tourist agriculture, sight viewing agriculture, etc. The processes of production are carried out in the strategy of entirely applying the biological nutrient cycle between soils and crops, strengthening the organic matter to enhance soil fertility, supplementing balanced essential fertilizers, avoiding overuse of chemical fertilizers, stimulants, toxic pesticides, phytoncides, avoiding heavy land preparation damaging the soil structure, processing the waste water sources before irrigating the fields...
            After along time of exploiting the soil, using a lot of fertilizers and chemicals... the farmers have returned to the blooming fields of green manure plants, flower gardens and ornamental plants that can be seen everywhere, enterprises of organic fertilizer production of all kinds and green and clean farms with healthy life environment. However, all in all, the core of the problem is to pay due attention to biological approach combined reasonably with the chemical one in order to maximally enhance the soil fertility to get a high quality and sustainable agriculture.
4. Some recommendations
            4.1. Yearly, in the whole country there many models of fertilizer production, experiments and on-farm demonstrations but they are conducted without planning and control. The department of Agricultural Extension (in cooperation with the National Institute for Soils and Fertilizers and the Vietnam Soil Science Society) has to form a central group to collect information and support management, and have a plan of broader agricultural extension.
            4.2. It is necessary to immediately carry out agricultural extension on balanced and reasonable fertilization for crops, formulae of fertilizer mixing, measures of solving the organic fertilizer problem, use of fouler fertilizers, establishment of fertilizer processing units in the rural areas, anti erosive measures, maintaining soil moisture and improving the soil.
            4.3. In the system of agricultural extension from Central to localities, it is necessary to have cadres specialized in fertilization - soil improvement.