17 Benny Hendricrianto Kurniawan Sigit Wicaksono Syahrul Kurniawan Journal of Animal and Plant Sciences JAPS 20262026 36 5 1018-7081 https://doi.org/10.36899/JAPS.2026.5.0111 <p class="MsoNormal" style="text-align: justify;"><span lang="IN">Variations in rubber production are thought to be influenced by differences in soil fertility. The study aimed to analyze and evaluate soil fertility variation in different rubber productivity. The research was conducted from January to June 2024 in Banjarsari Plantation, PT Perkebunan Nusantara I Regional 5 Jember Regency, especially at two contrast rubber productivity (i.e., high and low productivity). The classification of rubber productivity determined from the average rubber production during the last 3 years before the research, namely land with high productivity has a production &ge; 1,500 kg ha^-1, while land with low productivity has a production &le; 1000 kg ha^-1. All the research plot was located at 12-13 years old of rubber which is cultivated in monoculture systems, especially at clone&nbsp;</span><span lang="EN-ID">RRIC-100.</span><span lang="EN-ID">&nbsp;</span><span lang="IN">Soil sample were collected on a plot size 20 m &times; 20 m at 2 depths (i.e., 0-20 cm and 20-40 cm) of the high and low rubber productivity with 3 replications of each. Soil chemical properties were measured, including&nbsp;<a name="_Hlk192717753"></a>soil organic C, pH, total N, available P, soil exchangeable K, Ca, Mg, Na, Cation Echange Capacity (CEC),&nbsp;and base saturation (%). The study found that the land with high rubber productivity had 72-85% higher of soil exchangeable Na as compared to the land with low rubber productivity at 0-20 cm and 20-40 cm depths, as well as had 46% higher of total N at the top 20 cm of soil. In contrast, the land with low rubber productivity had 41% and 11% higher of soil exchangeable K and Ca as compared to the land with high rubber productivity, probably due to the high K and Ca uptake for supporting rubber production. Pearson correlation and&nbsp;</span>principal<span lang="IN">&nbsp;component analysis (</span><span lang="IN">PCA) test highlighted the significant relationship between functional elements such as soil exchangeable Na and latex production (r = 0.82, r table 5% = 0.497, p-value = 0.001). Therefore, increasing soil fertility through combining organic and inorganic fertilizer containing N and Na (e.g., potassium nitrate or borate fertilizers) &nbsp;can be helpful in areas with low rubber productivity for sustainable rubber production.</span></p> Monoculture rubber plantation; Rubber productivity; Soil chemical properties; Soil management Pakistan Agricultural Scientists Forum https://thejaps.org.pk/AbstractView.aspx?mid=2026-JAPS-97