SKCTION Vlll.— FACTORS INFLUENCING Bl.IOHT IMlKVAi.KNCI-;. 10.-> 



(8) The Naparima Marls or Black Soils of the Naparimas are 

 denved froiia a white infusorial marl. These soils include some of the 

 best sugar lands in the country and usually, but not always, contain a 

 good percentage of lime. They are easier to work tlian the red clay 

 soils and produce larger crops with less effort, particularly in wet years 

 when the red soils suffer from lack of drainage. They ara however, 

 rather heavy soils, and sometimes suffer from being too shallow, the white 

 subsoil being occasionally exposed even in shallow field drains. Sucli 

 thin soil fields should be submitted to a course of gradually deepening 

 mechanical cultivation through many years. 



The greater bulk of the soils of Trinidad are noticeable for the 

 almost complete absence of small stones, which tends to increase the 

 difficulty of drainage and aeration. In the Naparimas, where soil 

 clianges occur rapidly it is unfortunate that in many cases the boundaries 

 of the fields do not follow the boundaries of the soils, so tliat fields often 

 contain two distinct types of soils which require different treatment, a 

 condition which adds greatly to the difficulty of adopting extensive 

 cultivation by animals or tractors. 



Influence of Soil on Blight. 



In the flat parts of the Northern and Central sugar districts the soil 

 is usually more or less uniform over large areas, and one finds also that 

 the blight is often uniformly spread over whole fields or even larger 

 areas if otherwise similar. In the Naparimas on the other hand the 

 soil is more irregular and the blight more patchy. It was noticed many 

 years ago that injury was always more severe on the red soils than on 

 the black. Sometimes a red soil field is badly damaged alongside a 

 black-soil field which is untouched. At other times part of a field is 

 damaged and this is found to be a different and poorer type of soil. 



A few examples might be given here. 



(1) A field on La Fortunee Estate was very severely damaged in 1918 

 by froghoppers, but it was noticed that a band of canes across the field 

 was much greener and less injured, a. year later when the field was 

 ploughed up, this was found to correspond to a belt of black soil across 

 the field, the rest of which was red soil. 



(2) The "Government Pond" field at Hermitage Estate has for three 

 years in succession been damaged on one part only. The limits of the 

 damage (with the exception of the canes immediately below the pond 

 which are affected by seepage) correspond exactly to an outcrop of a 

 heavy clay. 



(3) On another field (36 D.) at La Fortunee Estate in 1918, on a slight 

 ridge, the eastern slope was a black soil, and the canes on it were 

 healthy and contained scarcely any froghoppers. The western slope 

 was a red clay and here the canes were severely damaged and frog- 

 hoppers abundant. 



(4) A very striking case is shown in the accompanying map of Cedar 

 Hill Estate (Fig. 27). On this estate the black soils are in a band 

 across the middle of the estate, while the northern and southern ends 

 are both red clays. Records kept of the fields damaged in 1900, 1912, 

 and 1919 show that they were all without exception on the red soils. 



