1. Exchange of information
The Seminar recognizing that calcareous soils are very extensive in the Near East Region and are a major resource for increasing agricultural production, recommended that FAO compile the information available on the effective use of these soils and secure an exchange of data between the countries of the region; it is further recommended that research still needed be conducted jointly by interested countries and FAO in the framework of the FAO/UNDP Near East Applied Research Programme.
2. Characterization of calcareous soils
With a view to making comparative studies of the use of calcareous soils in the region, it is recommended that the concept of calcareous soils be more precisely defined and that the description of these soils be expressed in standardized terminology. It is recommended that, in addition to usual field description and laboratory analysis, the amount of CaCO3, the form in which it is present and its distribution in the profile be recorded along the following lines:
a) Morphological characteristics
i) Vertical and lateral variations of the distribution and accumulation of limeb) Physical and chemical characteristics- diffuse distributionii) Vertical and lateral variations of lime content, and kind of carbonates (e.g. CaCO3, MgCO3, dolomite)
- discontinuous accumulation- pseudo mycelium- continuous accumulations (crusting)
- friable nodular
- hard nodular- non platy crusting with massive or nodular structure
- platy crusting in the form of calcareous crusts or compact slabs
- laminated crusting or ribboned pellicule (thin lime pan)iii) Texture of both the calcareous and non calcareous fractions of the surface horizons.
The morphological characteristics should be complemented by physical, chemical and mineralogical characterization. In addition to routine analyses the following characteristics should also be determined: the particle size distribution of the CaCO3 and its activity, bulk density and strength - especially of the surface horizons, moisture characteristics, exchangeable cations and micro-nutrients, measurements of salinity and alkalinity, content and type of organic matter and composition of clay-minerals.
3. Soil correlation
With a view to assessing the availability of land for development, it is recommended that the countries of the region pursue the survey of calcareous soils and that in order to allow for an exchange of experience, the classification system used for mapping be correlated using the FAO/Unesco Soil Map of the World legend as a common denominator.
4. Land use evaluation
With the mapping of calcareous soils it is required that the characteristics of importance for agricultural development be recorded. It is recommended, therefore, that the relationship between soil properties, morphological characteristics mentioned under No. 2 and their effect on crop .growth, and soil and water management practices be established under specific environmental conditions and be used for land use evaluation purposes at different levels.
5. Soil testing
The Seminar noted promising results established by soil testing methods which have been developed recently, recommended that a comprehensive soil testing system be adopted for recommending fertilizer applications and that the calibration and interpretation of each test be checked under local conditions, with special reference to calcareous soils. The Seminar further noticed that there is a need for guidelines on standardization of analytical methods for calcareous soils and recommended that an expert panel be convened on this subject.
The residual effects of applied nutrients should also be studied through soil testing and the yield response of successive crops.
6. Research needs on P nutrition
Considering the following four factors which could be important to P uptake:
a) the capacity factor which represents a measure of the amount of P from the solid phase that will enter the soil solution for a unit change in its P concentration,7. Research needs on N nutritionb) the intensity factor, usually expressed as the concentration of P in the soil solution,
c) the diffusion coefficient of P in the soil or soil solution, and
d) the demand for P by the plant top and the nature of the root system, i.e. its absorptive properties, noting that some of the variables which control P uptake by plant roots can be combined in equations that describe the conditions existing when a nutrient diffuses to a root system, realizing that little information is available on how to measure the capacity factor and the diffusion coefficient of P in highly calcareous soils, it is recommended that:
a) work should be carried out to determine changes in the capacity factor progressively with time according to the type of P fertilizers, andb) any further research on P nutrition with special reference to its economic application and on the interpretation of soil testing results should be carried out on the basis of new concepts on how soils supply P to roots.
It is recommended that research be conducted on Nitrogen nutrition under cultivation with particular reference to the three following points:
a) Nitrogen losses8. Research needs on organic matter- Loss or transfer of NO3 from applied fertilizers under irrigation and during periods of high rainfall, taking into consideration soil properties (depth, permeability, organic matter content, etc.) and the amount of N applied.b) Nitrogen balance under different crop rotations and form of fertilizers.- Loss of N as NH3 through volatilization, taking into account pH, CaCO3 content, moisture content, temperature, porosity and texture, rate of nitrification, etc.
- Loss of N by dentrification in relation to organic matter, organic amendments, moisture content at various depths, aeration and pH.
c) Nitrogen fixing organisms and role of azotobacter in N nutrition under rainfed conditions.
It is recommended that research be conducted on the role of organic matter in calcareous soils with regard to structural stability and availability of nutrients (especially P and micronutrients). Concurrently the most efficient method of application, amount, source and form of organic matter should be investigated.
9. Research needs on micronutrients
It is recommended that research be conducted on the supply and availability of micronutrients in calcareous soils with special reference to the critical levels that have been established for zinc, iron, manganese and copper which are respectively 0,5, 4.5, 1.0 and 0.2 ppm. Further work is required on the use of soil tests for boron and other elements in relation to levels of both deficiency and toxicity. Special consideration should be given to the relation between phosphorus and micronutrients.
10. Irrigation practices
The Seminar recognizing the importance of sound management of the soil and water resources in general and for calcareous soils in particular, and noting the specific properties of these soils and the role they have in affecting their productivity recommended that:
- in studying soil/water/plant relationships the CaCO3 content and its particle size distribution be taken into account in determining the soil texture and that more investigations be carried out on the active fraction of CaCO3 and its role in these relationships;11. Surface crusting- irrigation practices should take into consideration the moisture characteristics, crusting sensitivity to slaking and compaction and morphological characteristics of these soils;
- investigations should be made on the crop response to moisture and its role in nutrient and salt movements and chlorosis;
- irrigation methods, other than the conventional ones, should be used whenever possible to avoid land levelling of shallow soils and to conserve soil and water resources;
- the use of low quality water on calcareous soils should be investigated with a view to determining the susceptibility of calcareous soils to secondary salinization.
It is recommended that field treatments be investigated to prevent the problem of surface crusting. Applications of H3PO4, for example, and other practices should be examined and if proved effective, equipment should be developed for their application at the time of planting.
12. Tilth
It is recommended that machinery needed for tillage and terracing operations be tested in relation to soil properties bearing in mind plasticity indices; special reference is made here to heavy equipment required for land reclamation and other land uses, including the breaking of lime crusts and hard pans. Furthermore, the economical feasibility of breaking lime crusts should be investigated in each case.
13. Suitability of crops
With a view to obtaining optimum yields on calcareous soils, it is recommended that crops and varieties be selected which are adapted to calcareous soil conditions; this adaptation of crops may, in many cases, be no less effective than the application of soil amendments. It is further recommended that the study and use of indicator plants grown on calcareous soils be encouraged in a similar way to those grown on salt affected soils.
14. Extension
It is recommended that in order to make full use of available knowledge on properties and management of calcareous soils, extension programmes be strengthened with the purpose of bridging the gap between farmers and researchers and keeping the farmers informed of recent developments. Research efforts should be aimed toward the solution of practical problems in field situations, using the basic theoretical and experimental research as a guide. Approximations should be devised to enable extension specialists to recommend water and fertilizer requirements for direct use by farmers.
15. Regional Applied Research Programme
The Seminar recognizing that the action needed for the implementation of its recommendations will require inter-country coordination, recommends that this implementation be carried oat in the framework of the FAO/UNDP Near East Applied Research Programme and expressed the hope that this programme, which is now in its first phase, will be further developed with the support of the UNDP and that FAO use its good offices to expedite early action in this respect.
