The physical, chemical and mineralogical characteristics of soils in the western region of the State of Sao Paulo (Paulista Upland), where the largest number  of rubber  plantations  in Brazil is concentrated, are described. Rubber trees (Hevea brasiliensis  Muell Arg.) are planted in dystrophic and alic Dark Red Latosol, medium texture (Haplustox) and in dystrophic and eutrophic abrupt Podzolic Red-Yellow, Tb, soil, sand/medium texture. The high effective depth, which permits good water retention, is favourable for rubber culture. The major limitations of these soils are the low nutrient content of Latosols (Haplustox) and the high susceptibility to erosion of Podzolic soils (Karihaplustalf). These limitations may be compensated for by fertilizing and liming and by using conservation measures.

Natural rubber (NR) on chlorination turns into a white thermoplastic material which is widely used by the paint and lacquer industries taking advantage of its improved ageing properties, flame retardance, adhesion to various substrates etc. A major impediment in the manufacture of chlorinated natural rubber is the gel content of raw NR which makes preparation of solution difficult. In this study this problem has been solved to a great extent by using depolymerised liquid natural rubber (LNR). Substantially higher amounts (upto 20%) of LNR could be dissolved in carbontetrachloride to obtain a liquid mass that could be stirred and homogenized during the course of chlorination. This has resulted in manifold increase in the output compared to conventional method of chlorination of NR solution. Properties of the product have been found comparable with chlorinated rubber prepared from raw NR.

Infestation of the leaves of budwood nursery plants of Hevea brasiliensis by the weevil  Hypomeces squamosus F.   was  noticed  for  the first  time at Sarutari Farm,  Assam  in March,  1989.      The infestation  index   was   recorded  for   three consecutive years  from  1990.  Highest infestation index   and  maximum number of weevils  per  plant  were  observed  in the month  of April.

Wintering  pattern and  floral   biology of  25 clones of Hevea brasiliensis were studied  in two consecutive years.  Most of the modem  high  yielding  clones  were  found   to  exhibit partial wintering.   The intra-clonal differences  in  the maturity  of male and female flowers seem to play a major role in the prevalence of out crossing.  So, while selecting parents for a polyclonal seed garden, care should also be taken to ensure that the peak periods of maturity of male and female flowers overlap as  far  as possible.   Flowering  in 1995 was accomplished two to six weeks in advance than during 1994. The continued drought and soil moisture stress experienced from December 1994 onwards might be the main factors which  induced an  early wintering and flowering in 1995. The early flowering during 1995 has triggered a second round of flowering during the same  season, resulting   in  an  extension of  the flowering period.

C 0₂ assimilation rate (A), leaf area (LA ) and dark respiration rate (Rd) were determined  in ten Hevea brasiliensis Muell. Arg. genotypes, with contrasting yield potentials using juvenile plants (ca. one year old) grown under field conditions. Trees (ca. 12 years old) belonging to two of these genotypes were used to examine the same parameters. The parameters of juvenile plants were compared with those of the mature plants, together with their yield potential. The total leaf area per whorl (La) and the mean daily A and Rd of juvenile plants significantly varied amongst the ten genotypes. These parameters, together with the water use efficiency (WUE), determined  at leaf level of juvenile plants, were partially correlated with the ranking of clones for their yield, whilst the apparent quantum yield was significantly correlated (rs=0.65) with the same. The C O₂ assimilation capacity of a whorl [(A-Rd)La], and the daily gross photosynthetic integral of mature plants,  predicted  from the parameters  of juvenile plants also appear  to be high in the high yielding  genotypes,  with  the exception of RRIM 600. Possible reasons for this exception are discussed.    It is apparent that   genotypic differences in the parameters related   to yield determinants and the canopy photosynthesis of mature plants could be predicted   using their juvenile counterparts.   Juvenile plants could be used to predict the genotypic differences in parameters related to yield determinants in the mature plants and these juvenile parameters can be used for screening new genotypes at an early stage of their growth. Establishing genotype environment interactions, if any, for yield determinants of juvenile plants will further improve the possibility of using them for screening genotypes for yield.

Treatment of rubber wood by diffusion process using sodium pentachlorophenate in combination with either zinc sulphate or copper  sulphate was found  to be very effective for the preservation of both fungal and insect attack. Zinc sulphate or copper sulphate can be considered as a substitute for borax,  boric acid combination against  insect attack  in the  preservative treatment of rubber wood. It was found  that single stage diffusion process after two consecutive dippings in sodium pentachlorophenate and in either zinc sulphate or copper sulphate is equally effective as two stage diffusion process,  first with  sodium pentachlorophenate and  then  with  either  zinc sulphate or copper sulphate.