Source document: https://docs-lawep.s3.us-east-2.amazonaws.com/1696591411272.pdf (Zimbabwe)
INSTITUTIONAL PROFILE HISTORICAL BACKGROUND The foundation of the present day Chemistry and Soil Research Institute was laid in 1909 when an agricultural chemistry laboratory, which later became the Chemistry Branch, was established in the then Department of Agriculture.
From the onset it provided a comprehensive analytical and advisory service to the farming industry and also investigated a variety of problems- as a steady stream of articles in the early volumes of the then Rhodesia Agriculture Journal showed.
As the economy of the country expanded, particularly after the Second World War, and intensification of land-use increased the need to apply scientific principles to land selection and management, so the range of activities within the branch and the need for specialization increased.
Thus, in 1948, the growing demand for soil surveys of land-settlement and irrigation projects made a separate soil survey section necessary, in which staff could devote their whole time to Pedological studies and the development and standardization of criteria for land-use capability.
A few years later, a small soil fertility research section was formed with the initial objective of establishing suitable methods for determining the available nutrient status of soils of the country and correlating assessments of soil fertility with fertilizer requirements, as determined in field experiments.
The marked success that attended this investigation led to the setting up, in 1957, of a separate soil testing section to provide an advisory service to farmers and an analytical service to research stations.

The following year the research section began work on the in soil productivity, namely soil moisture complementary physical factors relationships and this eventually led to the establishment of the present soil physics section.
Meanwhile research on specific aspects of soil fertility made good progress and, to reinforce this, the newly-formed Agricultural Research Council of Central Africa set up in 1962 a Soil Productivity Research Unit in Marondera which assumed 1 responsibility for the more fundamental approaches to soil fertility research, embracing chemical, physical and microbiological aspects.

However, the Branch continued to investigate ad hoc problems as they arose and also to work on soil- plant-moisture relationships.
When the council ceased to exist in 1967, its unit in Marondera was taken over by government and attached to the Branch.

The present name of the Branch was adopted in 1965 to reflect more accurately the expansion of its activities to include field and laboratory studies that went far beyond the purely chemical.
Thus the present-day responsibilities of the Branch fall into five distinct, though closely interrelated, sections, namely: (i) Agricultural Chemistry, including a general analytical service for all materials except soils, (ii) Soil Testing, including ad hoc soil fertility investigations, (iii) Pedology and Soil Survey, (iv) (v) Soil Productivity Research Laboratory, and its functions will be discussed in Soil Physics more detail under these functions.
AGRICULTURAL CHEMISTRY SECTION General Analytical Service There are few aspects of modern technical endeavor to which the analytical chemist is not the indispensable servant, and agriculture is no exception.
All the materials the farmer uses to feed, water and protect his crops and livestock, and the products he grows, require analysis at some time or other to ensure their quality and suitability for particular purposes; and when things go wrong and malnutrition or poisoning is suspected, chemical analysis is an essential diagnostic aid.
As agricultural production becomes more intensive, the demands on the chemist increase and the analytical service must expand and keep abreast of the latest developments in analytical techniques.

2 The laboratory normally analyses between 3000 and 4000 samples a year, excluding soils.
These comprise fertilizers and liming materials; farm feeds and plant products; animal products, including blood, sera, and excreta from animal nutrition experiments; water for irrigation and livestock; oils and oilseeds, crop and animal protection products; toxicological specimens; and other agricultural materials.

Approximately half of these samples come from research stations and branches of the Ministry in connection with experiments on crop, pasture, and animal production, and various types of survey.
An appreciable number are also submitted by the Department of Veterinary Services for diagnostic and investigatory purposes.

Increasing use is being made of modern instrumental techniques, particularly in some of the more specialized aspects of the work, which will be discussed section are provided with later, and spectrophotometric (including atomic absorption), spectrographic, and chromatographic equipment.
laboratories of the the Analytical Investigations To maintain an efficient analytical service new methods have to be proved or developed, both for regular routine use and to deal with unusual materials or problems.

Problems also frequently arise that call for special analytical surveys, and these often require preliminary investigation of suitable methods of sample preparation and analysis.
Plant nutrition While soil analysis has proved an effective means of assessing the major nutrient requirements of field crops, it is not equally satisfactory for orchard and plantation crops, partly because of the difficulty of obtaining a soil sample representative of the whole root-zone when fertilizer is applied in tree basins.

Leaf analysis is a better index of the nutrient status of such crops and a more reliable guide to their requirements for optimum growth.
However, it is first 3 necessary to establish standards of leaf composition for high-performance trees, with specific upper and lower limits for each nutrient.

Unfortunately, the usual method of correlating yield response with nutrient content in fertilizer trials covering a wide range of conditions is not practical in the case of plantation crops, because of the time and expense involved.
Instead, the Institute obtained the data by a leaf-analysis survey of high-performance trees, under a wide range of fertilizer rates, in a large number of plantations in different localities, over a number of seasons; the highest and lowest values obtained for each nutrient in this way were used to approximate to the limits required for maximum production.

The same approach was applied to coffee and deciduous fruits with active collaboration of growers.
In the laboratory, nitrogen, phosphorus, potassium, Sulphur, and boron are determined by chemical analysis, and calcium, magnesium, iron, Aluminium, manganese, copper, zinc, and nickel by spectrometric methods.

Similar foliar analyses are also used for the diagnosis of suspected nutritional disorders in growing crops, using wherever possible material from affected and unaffected plants as a basis for comparison.
This service is available, where necessary, to farmers and is administered by the soil advisory service, to whose work it is complementary.

Salt-balance Studies When large-scale irrigation is practiced in semi-arid regions such as south- eastern Zimbabwe, it is vitally important to know whether or not salts are tending to accumulate, that is, whether the system as a whole and its component parts have a positive or negative salt-balance.
To measure the salt- balance it is necessary to determine the amount and salt content of the water applied to each catchment in the scheme and also of all regeneration water draining through the soils into the natural drainage system.

This was done for several years of fifteen catchments of the Triangle Sugar Estates, with the company doing the gauging and sampling, while the Institute was responsible for chemical analysis and interpretation of data.
4 SOIL TESTING SECTION The soil testing service is based on two fundamental principles: firstly that chemical methods of determining plant-nutrient availability and criteria for assessing fertilizer requirements must be founded on critical field experiments conducted under the same range of environmental conditions as those under which crops grow; and secondly that full cognizance must be taken of the past history and present state of the land when interpreting soil analyses and making recommendations.
The first of these principles was met by comparing crop responses in field experiments, carried out by the research stations of the Department and the Tobacco Research Board, with the availability of the major nutrient elements, as determined by various methods, and selecting the method for each nutrient that gave the best correlation.
After establishing in this way a method for making reliable predictions of when responses could be expected to each nutrient, the optimum fertilizer requirements were determined by correlating responses to fertilizer nutrients with the available nutrients in the soil.
This work continues indefinitely in order to refine existing criteria, to check the validity of criteria when applied to new varieties with higher yield-potential, and to establish criteria for hitherto minor crops when they assume greater economic importance.
Picture showing mineral nitrogen determination 5 The analytical methods adopted include a two-week incubation for determining available soil nitrogen, which is rarely used elsewhere for routine advisory work, presumably because it is regarded as too exacting and time- consuming.
However, its use is considered fully justified by the good correlations obtained between total mineral nitrogen (nitrate plus ammonium) present after incubation under controlled temperature and moisture conditions, and the amount of nitrogen available to early-planted crops during the growing season, as determined in miniature lysimeters and from crop- nutrient uptake studies.
To obtain the necessary information about the history and state of the land, completion of a detailed questionnaire on each sample is insisted upon, and farmers are encouraged to visit the laboratory personally to discuss their requirements and problems.

Format of the soil analysis results and lime and fertilizer recommendations from the Soil Testing Laboratory 6 The advisory work of the section is strongly seasonal in character.
Approximately 4000 samples are analyzed annually, and of these the vast majority are received and dealt with during the dry season.

However, the section also provides an analytical service for research stations of the Department and, to a lesser extent, for other scientific organizations; at present some 1000 samples are analyzed annually, mainly during the summer months for compilation of research data.
Apart from this indirect involvement in research, the section also undertakes investigatory work of its own, especially to follow up problems that have been revealed in the course of its advisory activities.

A considerable amount of laboratory work has been done on improved methods of determining lime requirements in different soils groups, new methods of analysis are constantly being examined, and nutritional problems are investigated in the greenhouse.
New fertilizer products are being evaluated under Zimbabwean soil conditions and these include from other countries such as Iran, China and Italy.

In the field, fertilizer experiments are conducted on subjects of immediate practical interest, usually in collaboration with farmers or large estates and sometimes also involving staff of the fertilizer companies or AGRITEX Department.
This type of field experimentation is essential, because it is becoming increasingly difficult to find soils of suitable fertility status on research stations, and in any case wide replication of experiments throughout areas where the particular crop is grown is desirable.

It is also essential to make evaluations under farmer field conditions.

Current experiments include high-formulation basal fertilizers, evaluation of slow-release N-Force fertilizer from Puccioni Fertilizer Company, Italy.
7 PEDOLOGY AND SOIL SURVEY SECTION In soil investigations, especially those concerned with fundamental classification and assessment of land-use capability, there are many questions that can only be answered in the field, where one can examine the properties of the undisturbed soil profile, down to the parent material.

However, even this is not enough.


The soil profile can only be fully understood in the light of knowledge about the climate under which it has been formed, the vegetation it supports, the present relief of the landscape of which it is a part, and the geomorphological processes by which that landscape has evolved.
All this is the province of a Pedologist, whose job it is to try to understand the equilibrium between the soil and its natural environment and how the soil will react when man alters that environment by the land-use he imposes on the soil.

In the early years of its inception, no major development project sponsored by Government got beyond the early planning stage without a soil survey conducted by this section to assess and map the suitability of the soil for the purpose intended.
Since most of the land-use surveys require semi-detailed, or even broader, reconnaissance of large areas, it has enabled the pedologists to acquire an extensive knowledge of many of the remote parts of the country.

For example, over 1,000,000 hectares have been mapped in the Zambezi Valley and in the Lowveld south of the watershed.

Normally on land-use surveys soils are described in terms of ad hoc units as closely related as possible to fundamental, i.e.
taxonomic, units and they are mapped in terms of these units or associations of them.

This ad hoc classification provides a permanent scientific record of the soils and may later lead to the definition of soil series.

For the primary purpose of the survey, however, these Pedological units must be interpreted in terms of land-use capability classes appropriate to the purpose of the project.
Since most of the development projects examined are based on irrigation, a standard system of assessment of the suitability of the soil for irrigation has been developed in the 8 light of experience in Zimbabwe and elsewhere to meet local conditions and needs.

This system is based mainly on the physical and chemical characteristics of the soil profile that determine texture, permeability, drainage, and available water capacity, but topographical features are also taken into account.
Collaboration with the Inter-African Pedological Service resulted in the production of the Soil Map of Africa South of the Sahara.

From this project emerged the broad principles from which Zimbabwean soils were realistically and significantly related to each other and also to the soils of other African territories.

This led to the publication of the first taxonomic description of Zimbabwean soils and an entirely new soil map in 1966.
The system of classification evolved taking into account both the properties of the soil and the manner in which it has been formed.

Thus the criteria used for grouping soils are observable or measurable properties, but they are selected and arranged in order of importance so as to reflect the effects of soil-forming factors that are thought to be responsible for the genesis of the soil.
On this basis, eight major soil groups are recognized in Zimbabwe and these are differentiated primarily on the basis of the degree of weathering of the parent material, the degree of leaching that the weathered material has undergone, and the degree to which weatherable minerals remain in the soil, and secondarily on the over-riding influence of excessive wetness, sodium or salt influence, shallowness, or paucity of weatherable minerals in the parent material.
Many of the chemical, physical and mineralogical properties of soils that are significant to agriculture are correctly reflected in the soil groups, and the system provides a better basis for describing and discussing agricultural soils than anything available in the past.

The studies that have produced the soil classification also inspired other related studies.

Such studies included assessment of sodic and hydromorphic soils, with important implications on the genesis of granite-derived soils generally.
The studies went further to investigate the chemical and mineralogical change from fresh granite, through weathering granite, to the 9 present-day soil, and examining the catenal variations in granite-derived soils, that is, the progressive changes from uplands to lowlands (vleis).
In addition to these fundamental studies the effects of long-continued irrigation with municipal sewage effluent were pursued, in regard to changes in both the soil and the regenerated water that eventually enters public streams.

With the increase in the population of urban areas, the disposal of these effluents is a matter of growing concern.
Since they carry high concentrations of plant nutrients, they are either a potential asset, if they can be used agriculturally and the nutrients taken up by crops or absorbed by the soil, or they are a potential menace, if they enter rivers and lakes where they cause accumulation of plant nutrients and excessive growth of algae and aquatic plants such as occurred in Lake Chivero.
Soil Physics unit In a country where rainfall is unpredictable, except with broad limits, the importance of understanding crop water-use in relation to soil-moisture availability cannot be over-emphasized, since this underlines the correct selection of crops for different ecological regions and the planning of irrigation programmes.

It is understandable, therefore, that the main efforts of the field of soil physics research have so far been conducted on soil-plant-moisture relationships.
Initially, data were collected on water-use by Lowveld irrigated crops under optimum soil-moisture conditions and some observations were made on the effect of moisture shortage.

The logical trend in this research was followed in Harare, where work was done on the effects of moisture shortage at different stages of growth on plant development and yield.
Precise knowledge on of crop water requirements enables one to fit crops into the different types of natural season occurring in the country and to assess the probable pattern of the season, or season-type, is known for each ecological region.
A definition of season-type, in terms of the probable dates of start and 10 end of the rainfall season and the probability of drought occurring within it, is therefore desirable and would, moreover, have many uses, in other fields such as general agronomy and pasture and animal production.

Research has been on-going on water use efficiency with small-scale irrigation technologies such as drip systems.

Soil water conservation under no-tillage, conservation agriculture, and mulching have been pursued.
Soil chemical and physical properties have been found to improve under these agricultural practices.
Small-scale drip irrigation demonstration of ‘crop-per-drop’ and measurement of soil water with neutron moisture meter 11 SOIL PRODUCTIVITY RESEARCH LABORATORY This section is primarily concerned with the fundamental problems of how to increase or maintain fertility under more intensive systems of cropping, especially on the inherently less fertile soils, where shifting cultivation or short term cropping interspersed with grass fallows has traditionally been practiced.
The problems studied fall into three groups according to the cropping history of the land; firstly there are the problems encountered in the opening up of new lands, then changes that occur during continuous cropping, and finally the problem of how to reclaim worked-out soils.

While not directly concerned with advisory work, this section also investigates new soil fertility problems that become significant, in collaboration with the advisory service of the Institute and AGRITEX.
To study changes in soil fertility during long-term cultivation, chemical, physical and microbiological factors are studied by a research group working in close cooperation with each other.

For these long-term project samples are obtained from the field trials of research stations, while for studies that require work on a wide range of soils or are specific to an area or cropping system, special field trials are carried out on farms, in collaboration with the farmers concerned and AGRITEX.
On soils where nutritional disorders, and in particular trace-element deficiencies, are being studied, pot trials are done in the greenhouse, so that only the treatments most likely to be significant are applied in the field, thus enabling the most efficient use to be mad of widely scattered trials.

Long-term changes in soil fertility on sandveld are being studied in trials laid down by the Grasslands and Makoholi Research Institutes.
Maize is grown repeatedly and differential nitrogen, lime, and manure treatments, with basal phosphate and potash, are applied each year.

Inoculation of legumes is essential in new lands and work is being done on the survival of rhizobia introduced into the soil and the persistence of their ability to form nodules.

Other work in the microbiological field is concerned with the 12 increase in soil-borne pathogens when infection is accidentally introduced through crops.
Since soil acidity is frequently associated with infertile soils, a large number of experiments have been carried out to determine how effective liming is in restoring fertility and also to estimate the desirable pH range for maize.

In all of these experiments soil and foliar samples from plots with different lime treatments were analyzed to indicate what lime does to the crop and what nutrients are likely to be deficient in acid soils.
It has been found that, in general, lime reacts rapidly, but its effect is limited to the soil in the vicinity of the zone of incorporation and a high proportion may be lost by leaching from sands.

In the period between 1994 and 2000, the institute carried out research on integrated soil fertility management in the smallholder sector of Zimbabwe in a project funded by Rockefeller Foundation.
Soil nutrient mapping, with the objective of developing a diagnostic, recommendation and integrated system (DRIS) was carried out in a number of districts of Zimbabwe.

A total of 3500 farmers’ fields were sampled in the 1994/95 to 1999/2000 seasons.

Farmers with the least use of mineral fertilizers had the lowest P levels in their fields.

Nitrogen, phosphorus and zinc were limiting in over 70% of the sampled fields.
However, even in those fields with reasonable P build-up, maize yields were low indicating that other nutrients were limiting (Table 1) 13 Table 1: Maize yields against soil P and pH values in DRIS fields in Murewa area (Ngomamowa, Makuvaza, Chinhoyi and Chanetsa Wards) in 1994/95 season Group Classification based on soil P level P2O5 (mg/g) pH value (0.01M CaCl2) Grain yield (t/ha) Stover yield (t/ha) % of farmers Very poor 0-18 4.33 Poor Bad 19-30 4.62 31-42 4.60 Average 43-54 4.62 Good 55-66 4.65 Very good 67-78 4.50 2.17 2.81 3.16 3.43 3.33 2.33 Very high >80 4.66 - 2.48 3.22 4.12 3.48 3.87 3.49 - 17.98 32.58 20.22 15.73 3.37 6.74 3.37 Manganese (Mn) levels in the maize plants were sufficient to very high (152-225 ppm and 99-299 ppm in whole plants and in the cob leaf) in most plant samples, while soil pH levels were very low in most areas, indicating potential soil acidity problems (Table 1).
Magnesium (Mg) levels were low to acutely deficient (0.08- 0.20% and 0.07-0.13% in young plants and in the cob leaf, respectively) in almost all the fields sampled.

The situation was attributed to non application of lime as well as decreased use of manure by farmers over years.

For instance, the last time smallholder farmers used lime was in the early 1980’s, when it was distributed free by the Government of Zimbabwe as part of fertilizer input scheme.
14 Table 2: Soil acidity status (percentage of sites) in 12 smallholder areas around Zimbabwe Location pH range 4.14-4.19 4.20-4.50 4.51-4.84 4.85-5.61 Mhondoro Chivhu Wedza Zvimba Murehwa Nharira Buhera Serima Gokwe Zhombe 15 60 33 12 80 40 50 40 0 0 Chirimhanzu 41 Zvishavane Interesting experiments were conducted with composting rock phosphate (RP) with cattle manure resulting in improved maize grain yields on 31 smallholder farms around Dorowa Mine where rock phosphate is mined in Zimbabwe.
Three combinations were found to give the best results (Table xx), namely: (i) Manure (M) mixed with RP composted in cattle pens, 15 (ii) Manure + SSP (single superphosphate, 19% P2O5), and (iii) Manure + Compound D (7:14:7, N: P2O5:K2O) Table 3: Comparative net benefits (%) from manure composted with some mineral fertilizer materials with the farmer’s practice Fertilizer Material Increase in Net Benefits (%) over farmers practice Manure + Rock Phosphate composted in kraal (10t/ha) Manure (10t/ha) + SSP (150 kg P2O5/ha) applied in the field Manure (10t/ha) + Compound D @ 150 P2O5 kg/ha) applied in the field 38 71 87 The composted manure was enriched through an increase in N (by 42%), P (by 1907%), and Ca (by 159%) and a reduction in sand content by 22%, compared with non-composted manure.
Organic and inorganic fertilizer research The efficiency of pit storage (anaerobic composting) and conventional heaping of manure (farmer’s practice), with and without crop residues added, was studied on 11 farm sites in Murehwa (Nzuma and Murwira, 1998).

The total N measured in anaerobically composted manure at the end of three months’ storage was significantly higher than in aerobic composting systems without crop residues.
16 The Legume Inoculant Factory Zimbabwe has the second largest legume inoculant factory in Africa (after South Africa) which is located in Marondera at Soil Productivity Research Laboratories under Chemistry and Soil Research Institute.

The factory produces inoculants for grain legumes (soyabeans, cowpeas, groundnuts, sugarbeans and peas and pasture legumes (lucerne, lab lab, sunnhemp, velvet beans etc).

About 90% of the inoculants produced are for soyabeans.
The Soil productivity Research laboratory has a culture collection of strains of rhizobia.

The major commercial strains for soyabeans are MAR 1491 and MAR 1495.

An experiment was conducted to evaluate the effectiveness of MAR 1491 and MAR 1495 strains in soyabean production.

These were compared with strains isolated in Argentina, SQA 101 and SQA 123.
Picture showing autoclaving at 120oC and inoculation with rhizobia inoculants at Legume Inoculant Factory, Marondera 17 Fig 1 and 2 shows that MAR 1495 had the highest amount of nitrogen fixed and grain yield while the uninoculated treatment had the lowest amount of nitrogen fixed and grain yield.

Fig.

3 shows the visual difference between inoculated and uninoculated soyabean crop.

Figure 1.

Amount of N fixed (kg/ha) by different Bradyrhizobium japonicum strains at 12 weeks after planting Figure 2.
Soyabean grain yield (t/ha) from inoculation with different Bradyrhizobium strains 18 0102030405060708090uninoculatedMAR 1491MAR 1495SQA 101SQA 123Bradyrhizobia japonicum strainNitrogen fixed kg/ha012345uninoculatedMAR 1491MAR 1495SQA 101SQA 123Bradyrhizobia japonicum strainSoyabean grain yield in t/ha Picture showing inoculated and uninoculated soyabean crop 19 Current staff establishment of Chemistry and Soil Research Institute Designation Head of Institute Chief Research Officer Research Officer Chief Research Technician Research Technician Human Resources Assistant Administration Assistant Accounting Assistant Executive Assistant Sample Analyst Laboratory Hand Driver Office Orderly Total CONCLUSION Establishment 1 2 24 2 18 1 1 1 2 11 28 1 4 96 The various services offered by Chemistry and Soil Research Institute have helped shape the agricultural sector of Zimbabwe.
The institute remains pivotal to the sector.

More work still remains to make farming viable in the face of high costs of production emanating from prices of fertilizer and seed inputs, tillage and many other factors.

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