Browsing by Author "Dagg, M."
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Item The Agronomic Efficiency of the N.I.A.E. Mechanized Tied Ridge System of Cultivation.(1967) Macatney, J.C.; Dagg, M.A tied ridge system of hand cultivation has been practised successfully in parts of Tanzania for many years. Equipment to mechanize this system was devised and constructed by the National Institute for Agricultural Engineering, U.K., particularly for use in areas of marginal rainfall where water conservation is essential. Agronomic trials with this equipment were carried out on three soil types in Northern Tanzania. Records from resistance units showed much better penetration of rainfall under tied ridges than under flat cultivation. Corresponding yield responses in maize were only obtained when the increase in available water made an appreciable difference to conditions of water stress at the time of tasselling and silking. Weeding operations using a ridging body achieved a satisfactory control. After a few modifications to the equipment, especially the incorporation of a small tine to rip the bottom of the basins to improve infiltration, the system of cultivation based on ripping, ridging and tieing proved to be an adequate alternative to ploughing and harrowing for seed bed preparation, and a much more efficient method of water conservation.Item Cashew Nut Production In Southern Tanzania V-Water Balance Of Cashew Trees In Relation To Spacing(1967) Dagg, M.; Tapley, R.G.Cashew nut trees flourish at wide spacing in a rainfall regime of 900 mm. and evaporation of 2,000 mm., but mature trees produce little crop at close spacing, 20 ft. X 20 ft. The suggestion that this is due to water competition is examined quantitatively from an agrometeorological approach for conditions of full canopy.Item Coffee Board of Kenya Monthly Bulletins January 1965(1965) Coffee Board of Kenya; Pereira, H.C.; Dagg, M.; Hosegood, P.H,Measurements of the changes in the physical properties of top soils are reported from a 15-year factor all tillage trial in a plantation of Arabica coffee. Two monsoon-type rain seasons per year gave thirty cycles of soil wetting, weed growth, tillage and soil drying. Rainfall acceptance tests showed clean-weeding to ca see an average 15 per cent reduction of infiltration from very heavy rain storms, compared with the minimum weeding treatment.Item Coffee Board of Kenya Monthly Bulletins June 1971(1971) Coffee Board of Kenya; Dagg, M.Good soil management involves the provision of a satisfactory environment for roots,the suppression of weeds,the maintenance of fertility and the prevention of accelerated erosion.These aspects are,of course, interrelated and the complex environment of the soil has strong physical, chemical and biological interactions. However,in the drier tropics, two additional factors external to the soil have an important influence on soil management.High evaporation rates impose high levels of transpirational demand such that the water supply is often only marginally adequate,and the rainfall arrives at relatively high intensities, encouraging loss of water by surface runoff.Water conservation,therefore,becomes a dominant consideration in good soil management.Item Details of Hand Sampling Tool for Taking Undisturbed Soil Cores(1962) Dagg, M.; Hosegood, P. H.In many soil moisture investigations it is necessary to know something of the soil structure, such as the distribution of pore space, the stability of the soil, its ability to accept rainfall or similar physical properties of the soil. To study these parameters in the laboratory, samples of the soil, with its structure disturbed as little as possible, are needed (Pereira, 1955). In most soil research problems samples must be replicated several times and the large number of samples required makes carving out rectangular blocks of undisturbed soil a tedious task: a simple method is needed. To this end, a convenient hand sampler has been developed that cuts cylindrical cores of undisturbed soil. 4 in. in diameter and 3 in. high. This note presents a working drawing and description of this core sampler in response to several requests from research workers who wish to carry out volumetric soil moisture studies. No great originality is claimed for the design of the sampler which has had incorporated in it the better points of several existing designs (Coile, 1936), (Lutz, 1947), (Dortignac, 1950), (Swanson. 1950). However, it could be claimed that it is more convenient to operate than its predecessors and cuts a large core which is an important factor in reducing the variability in bulk soil parameters.Item The Effect of Different Cultivation Techniques on Soil Moisture Conservation and the Establishment and Yield of Maize at Kongwa, Central Tanzania(1971) Macartney, J.C.; Northwood, P.J.; Dagg, M.,; Dagg, M.; Ministry of Agriculture, Food and Cooperatives: East African Agriculture and Forestry Research OrganizationTwo years experimentation with different methods of cultivation for maize growing at Kongwa, Central Tanzania, are described. A ripping operation before the onset of the rains has been c hown to be an integral part of any cultivation system to provide for both water infiltration and to assist in root development on this compacted soil. A case is pre-iented for the adoption of a zonal tillage system with reduced surface cultivation, inter-row mulching and ripping.Item Equipment Modifications to a Mechanized Tied Ridge System of Cultivation(1968) Macartney, J. C.; Dagg, M.Increasing acreages of marginal land in East Africa are being brought under the plough using conventional commercially available equipment. Cultivations with high-speed disc implements on dry soil in the preparation of fine consolidated seedbeds has had a deleterious effort on soil structure, chiefly from the point of view 'Of soil and water conservation. [6] Although the benefits of tie ridging have been appreciated and proven under certain conditions in Tanzania, [7, 8, 9] cultivation policy and recommendations have not been possible through Lack of a suitable, fully tested system.Item Estimates of Evaporation in East Africa in Relation to Climatological(1969) Dagg, M.; Blackie, J.R.; East African Agriculture and Forestry Research Organization. Institute of Hydrology UK.IN preparing His map showing the climatic classification of East Africa, Sansom (1954) used the Thornthwaite (1948) system of classification and the Thornthwaite method of estimating potential evapotranspiration (or evaporative demand). The areas denoted as having moist climates appear to be optimistically large when compared with observations of the vegetational complexes there. Similarly, Carter (1954) used the Thornthwaite method of estimating evapotranspiration when preparing the water balances for selected stations in East and Central Africa, and Howe (1953) also used this method in preparing a climatic classification of Central Africa: his results also? Matthew Dagg, BSc, PhD, was until recently Head of the Physics Division of the East African Agriculture and Forestry Research Organisation. He is now Director of the Institute for Agriculture Research at Samaru in Nigeria. JR Blackie, BSc, MSc, is a senior Scientific Officer seconded to the East African Agriculture and Forestry Research Organisation from the Institute of Hydrology in UK.Item Evaporation in East Africa(1970) Dagg, M.; Woodhead, T.; Rijks, D.A.; East African Agricultural Research Organization: Cotton Research Corporation; Cotton Research StationFollowing a decision to estimate potential evaporation from meteorological observations rather than from evaporation pans, 53 agricultural meteorological stations were established over East Africa with the co-operation of several departments of three governments. Supplementary information from an additional 123 less well-equipped stations was incorporated into the preparation of maps of monthly potential open water evaporation, using the Penman estimate. Annual values of potential evaporation range from more than 2,600 mm to less than 1,400 mm with 70 % of the area of East Africa having potential evaporation rates of between 1,800 and 2,200 mm per annum. There are marked seasonal variations in evaporation rates, mainly dependent on patterns of cloud cover, but average monthly rates rarely fall below 90 mm even in highland areas. These high rates of water demand have serious implications for the management of water catchments, land "planning, crop breeding, tillage techniques, ground water recharge and rates of primary productivity in rangeland.Item Factors Affecting the Use of Evaporation Pan Data in East Africa(1969) Dagg, M.The Most Extensive Set Of Data On Evaporation In East Africa Is from Evaporation Pans And It Is Necessary Therefore To Consider How Best To Use this Information. In Addition There Are Some Supplementary Estimates of Evaporation from Meteorogical Observations, By the Penman Method, Which Can He Used In interpreting The Pan Data. A Casual Glance at the Pan Data Shows That It Would Certainly Be Unwise To Use the Evaporation Figures Directly and Unmodified. It Is Unfortunate That The Interpretation Of Pan Data Into Meaningful terms Is Not At All Straightforward, And It Must Be Appreciated That The Data Available For A Specific Pan Give The Amounts Of Water Lost By That Particular Pan Lin That Particular Environment. The Results Are Influenced By Pan Colour, Size, Shape And Exposure And The State Of The Environment Over Large Distances Compared With The Size Of A Meteorological Enclosure. The Pan Data Reviewed By Mcculloch (1961) Showed A Wide Variety Of Effects Of Exposure And Environment But These Were Not Discussed In Detail And It, Is Useful To Consider The Basic Processes Involved Before Examining The Performance Of Specific Types Of Evaporation Pan.Item The Impact of Water Management on the Tropical Environment(1964) Dagg, M.; East African Agriculture and Forestry Research OrganizationMan's impact on the environment through water control should be wholly beneficial and the manipulation of water resources is a very important element in his mastery of adverse living conditions. Primarily, the efficacy of rainfall can be controlled by man's use of the land surface, while disastrous cycles may be initiated through misuse of the land, particularly by overgrazing in dry or semi arid areas. Vegetation changes under such a regime are frequently very striking and appear to indicate a deterioration in the quantity of rainfall, when in fact they should be ascribed to a decline in the efficiency of acceptance of rain by the soil. Land use in high rainfall areas is important in regulating streams and maintaining dry weather flow for water users downstream. Improvement in the distribution of domestic watering points can have many beneficial effects on the environment even in areas of high rainfall. In areas of low rainfall, it is essential that there are effective means of controlling the numbers of grazing animals and the provision of water for stock must be carefully planned to match the carrying capacity of the land and the requirements of seasonal grazing if serious damage to the vegetative environment is to be avoided. To this end, the type of installation used in developing watering points is often of importance.Item The Physical Effects of Contrasting Tillage Treatments over Thirty Consecutive Cultivation Seasons(1964) Pereira, H.C.; Dagg, M.; Hosegood, P.H.Measurements of the changes in the physical properties of topsoil are reported from a I5-year factorial tillage trial in a plantation of arabica coffee. Two monsoon-type rain seasons per year gave thirty cycles of soil wetting, weed growth, tillage, and soil drying. Rainfall acceptance tests showed clean weeding to cause an average IS per cent. Reduction of infiltration from very heavy rainstorms, compared with the minimum weeding treatment. Where a grass mulch provided coarse organic matter for incorporation into the topsoil, a modified rotary hoe, described in a previous paper, proved even more successful than hand implements in maintaining soil structure. In the absence of grass mulching, the rotary hoe did more damage than the hand implements. The experiments demonstrated a sound technique for maintaining very good topsoil structure; Part III of this series showed that these methods also increase yields.Item A Study of the Water use of Tea in East Africa using a Hydraulic Lysimeter(1970) Dagg, M.; East African Agriculture and Forestry Research Organization, Nairobi KenyaA hydraulic lysimeter, 10 × 10 × 6 ft. deep (3.05 × 3.05 × 1.83 m), has been used to measure the monthly evapotranspiration over a period of 35 months from eight tea bushes planted to be uniform with an extensive area of tea at the Tea Research Institute of East Africa, Kenya. Tests on the performance of this inexpensive lysimeter showed it to be operating satisfactorily and capable of producing valid evapotranspiration data over periods of a few days. The tea was never under serious moisture stress and advection effects were likely to be minimal, with the fetch of the prevailing wind being over 30 km of evergreen moist forest. Monthly evapotranspiration rates (Et.) from the young tea crop varied from 40 to 115 mm per month, but were satisfactorily predicted (r = 0.85), both in wet and dry months, by the relation: Et.=Eo[0.9a+(1−a)0.9n] where Eo is the Penman estimate of open-water evaporation, a is the fraction of the soil covered by the crop at noon, and n is the fractional number of rain days per month.Item A Study of the Water Use of Tea in East Africa Using A Hydraulic Lysimeter(1970) Dagg, M.; Physics and Chemistry Division, East African Agriculture and Forestry Research Organization, Nairobi KenyaA hydraulic lysimeter, 10 × 10 × 6 ft. deep (3.05 × 3.05 × 1.83 m), has been used to measure the monthly evapotranspiration over a period of 35 months from eight tea bushes planted to be uniform with an extensive area of tea at the Tea Research Institute of East Africa, Kenya. Tests on the performance of this inexpensive lysimeter showed it to be operating satisfactorily and capable of producing valid evapotranspiration data over periods of a few days. The tea was never under serious moisture stress and advection effects were likely to be minimal, with the fetch of the prevailing wind being over 30 km of evergreen moist forest. Monthly evapotranspiration rates (Et.) from the young tea crop varied from 40 to 115 mm per month, but were satisfactorily predicted (r = 0.85), both in wet and dry months, by the relation:Et.=Eo[0.9a+(1−a)0.9n]where Eo is the Penman estimate of open-water evaporation, a is the fraction of the soil covered by the crop at noon, and n is the fractional number of rain days per month.Item A Study of the water use of tea in East Africa using a Hydraulic Lysimeter(1970) Dagg, M.; Physics and Chemistry Division, East African Agricultural and Forestry Research OrganizationA hydraulic lysimeter, 10 × 10 × 6 ft. deep (3.05 × 3.05 × 1.83 m), has been used to measure the monthly evapotranspiration over a period of 35 months from eight tea bushes planted to be uniform with an extensive area of tea at the Tea Research Institute of East Africa, Kenya. Tests on the performance of this inexpensive lysimeter showed it to be operating satisfactorily and capable of producing valid evapotranspiration data over periods of a few days. The tea was never under serious moisture stress and advection effects were likely to be minimal, with the fetch of the prevailing wind being over 30 km of evergreen moist forest. Monthly evapotranspiration rates (Et.) from the young tea crop varied from 40 to 115 mm per month, but were satisfactorily predicted (r = 0.85), both in wet and dry months, by the relation:....Item The Water Balance of Both Treated and Control Valleys(1962) Dagg, M.; Pereira, H. C.Continuous records of soil moisture tensions throughout the 10-ft. profile at stations representing the upper, middle and lower sectors of each valley have shown only brief annual periods of moderate stress in the first 6 ft.. with uninterrupted maintenance of wet-soil conditions below this depth although sampling has indicated withdrawal of water at all depths. Despite substantial changes in the water content of the total 10 ft. of soil, each I-ft. layer has held available water throughout the three years with 13 in. or more always available from the profile. The well-distributed rainfall exceeded the annual open water evaporation in each year of records: only one IO-day period without rain was recorded between April. 1957 and December, 1960. Under these circumstances a fairly constant relationship between transpiration and open water evaporation can be expected from a continuous canopy of evergreen forest.Item The Water-Balance of Bamboo Thicket and of Newly Planted Pines(1962) Pereira, H.C; Dagg, M.; Hosegood, P.HResults of the preliminary water use experiments at Kinale, in the same bamboo forest some 16 miles south-east of the experimental catchments, have been published elsewhere (Pereira and Hosegood, 1962) (1) but the main findings are relevant here. Direct measurements of water-use from 10 ft. depth of soil showed equal consumption by 120 ft. high 26 year old Radiata pine, 50 ft. high 16 year old Monterey cypress, 30 ft. high 10 year old "shamba" planted Patula pine (after clean weeding had ceased) and from the undisturbed indigenous bamboo thicket. In all cases the water use averaged approximately 86 per cent of open-water evaporation.
