Influence of soil moisture and nutrient status on fine root dynamics of rubber trees (Hevea brasiliensis)

摘要

Fine roots are important for water and nutrient acquisition and their dynamics have profound influence on the below ground resource capture efficiency of trees. The present investigation was taken up to study the effect of environmental variables viz., soil moisture and soil nutrient status on the fine root dynamics of rubber trees, and to find out the period of highest fine root density to optimize the timing of pre-monsoon fertilizer application. The study was conducted at two locations, Kottayam and Chethackal with distinct variation in soil nutrient status, comparatively lower status at Kottayam and higher at Chethackal. Root observations were recorded during 2006 and 2007. Soil moisture stress during summer season was less during 2006 comparedto 2007. At both the locations, the clone was RRII 105 and trees were 17 years old. Fine root density in the surface layer (0-7.5 cm) was quantified during summer season and after the onset of rains till the root density stabilized or declined. Soil moisture was recorded periodically. With the onset of rains, fine roots began to develop and the highest root density was observed after a period of 35 to 45 days at both the locations during both the years. After this period, the root density declined. Thefine root density was nearly twofold at the low fertility site (Kottayam) compared to the other site (Chethackal). The intensity of soil moisture stress during preceding summer season influenced the time taken for fine root development after the onset ofrains and the biomass allocated for fine root production at the low fertility site. When the soil moisture stress was low, there was gradual increase in fine root density, whereas, when the soil moisture stress was more, the time lag for initiating rootproliferation was longer. The data indicate the necessity of a more precise timing of fertilizer application to maximize uptake of applied nutrients.