| dc.description.abstract | The water us® study in high density oof fee he cam® a priority after coffee intensification showed promise as a means of increasing the crop production with apparently no increase in costs other than that of extra seedlings at th® time of establishment. This study was further prompted by the fact that the water resource may be a limiting factor in th® attempt to intensify coffee production by close spacing in some environments. While water use was the main subject of this study, it was thought that dose spaoing might have an influence on the properties of the topsoil. This led to the incorporation of subsidiary investigations on root distribution, water infiltration rates and soil bulk density.
The literature cited in this thesis shows that many of the advantages realized in the intensification of apples in the temperate countries are being demonstrated in coffee, a crop of tropical environments. High yields have been recorded in high density ooffee. Other advantages of close spacing in coffee, such as less need for weed control and pruning, have also been shown. The review also discusses crop water use and the methods used for measuring soil moisture. Similarlly, previous work on the subsidiary investigations is reviewed.
The work reported in this thesis addressed itself to the study of water use as distinct from water requirements, as no water was applied to the ooffee during the trial, except the
natural rainfall
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Two methods were used la tha study of tho ooil moisture chan gas, the cravimatrio and gypaun resistance block methods. Comparisons v;oro made with Eateorological eotiaatea of crop water uae*
Crovimstrio 3oil moiature datominationa v.ore made ovary 23 days, frcnx nid-April, 197$ to nid March, 1977* ^ator use in tha four coffee blocks was compared by sti -iatieal analysis of tha percentage ooil aoi3ture of tha oven-dry soil* The percentage soil moisture was also converted into tha quantity of crater in the looting mono in nillinutroa* This facilitated the comparisons of moisture changes at different sanpling date a.
Tha result3 cf tlda study, lad to the conclusion that, coffee density per og cay have no ol^iificant effect on the coil moisture* There vcia no evidence to tha effect that close spacing increased crop water use aa previously speculated* An intereating insignificant trend vras di30overed where coffee at hi{jier plant densities appeared to use logs tratsr than at lower densities*
3oil rater measurements U3ing tho ^ypsua resistance blocks wore made at weekly intervals* Thi3 procedure was designed to provide additional information to supplement that obtained by tha foioaoekly gravimetric soil samplings* Tha results followed tho jrae pattern as those of the gravimetric method* This strengthened the conclusion that there 13 no reason to believe that hi^i density coffee would impose a hi^ier demand on soil moisture*
Two motiiods rare employed in tlie otudy of coffee root distribution in the toprsll, tiis core o'-nplor :id tlsa trench*
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The core sampler method was used to taka samples at 0-6, 20—26 and 40-46 cm. soil depths. The trench ,method, on the other hand was used to take samples at 0—20, 20—40— and 40—60 cm. soil depths.
Tha results of the root distribution studies showed that, there were more roots per unit volume of soil below 40 cm soil depth in the intensive ooffee plantings, and the quantity of roots in tills 3oil layer increased as the ooffde density increased.
The water infiltration rates were studied by the double-ring method. The trials were carried out under two different soil conditions, dry and wet.
The results revealed great variations from p^ace to place. There was no consistent trend in relation to plant density. However, tha infiltration rates in the dry soils were generally hi^ier than those recorded when tha soil was wet.
The topsoil bulk density was studied by taking undisturbed soil samples, at four different depths, the bulk density being calculated as the ratio of dry weight (in grams) to the volume (in o.c.).
The topsoil bulk density (0-6 cm) was found to decrease as the plant density increased. This effect was more pronounced in the upper part (0—3 cm) of this layer.
The three blocks of intensive ooffee had been cropped four times by the time this trial was carried out. The yield data collected over four years was used to calculate the coffee yield per unit area and per tree.
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The results showed that close spacing very substantially increases yield por unit area* However, the yield per tree wa3 found to decrease with the increased plant density. This i3 in accordance with earlier work.
In spits of the occurrence of water stress, coffee quality was not affected by closely spaoed coffee to any greater extent than in conventional coffee.
It is concluded that the water resource is no more likely to limit the suitability of any climatic zona for hi$i density coffee that conventional densities have proved satisfactory. | |
