Soil Nutrient Status and Leaf Nutrient Norms in Oil Palm (Elaeis guineensis Jacq.) Plantations Grown on Southern Plateau of India
Oil palm is a heavy feeder of nutrients and requires balanced and adequate supply of nutrients for optimum growth and yield. Information regarding soil nutrient status and leaf nutrient concentration is very much required for proper fertilizer application. Therefore, a survey was conducted for assessment of soil nutrient status and leaf nutrient concentration in 42 oil palm (Elaeis guineensis Jacq) plantations in the state of Karnataka, situated in southern plateau of India. In surface soil layers, soil acidity (pH), electrical conductivity (EC) and organic carbon (OC) content ranged from 4.91 to 8.74, 0.10 to 2.54 dS m−1 and 1.17 to 28.9 g kg−1 respectively. The values of available potassium (K) (NH4OAc–K), phosphorus (P) (Olsen-P) and exchangeable calcium (Ca) (Exch. Ca) varied from 31.2 to 386 mg kg−1, 7.69 to 242 mg kg−1 and 156 to 1273 mg kg−1 respectively. The concentration of exchangeable magnesium (Mg) (Exch. Mg), available sulphur (S) (CaCl2-S) and hot water soluble boron (B) (HWB) ranged from 52.8 to 307 mg kg−1, 2.25 to 73.5 mg kg−1 and 2.29 to 16.0 mg kg−1 respectively. Diagnosis and recommendation integrated system (DRIS) norms were established for different nutrient expressions and it was used to compute DRIS indices. As per DRIS indices, the order of requirement of nutrients in the region was found to be K > P > nitrogen (N) > B > Mg. Optimum leaf nutrient ranges varied from 2.24 to 2.97 %, 0.08 to 0.14 % and 0.78 to 0.91 % for N, P and K respectively, from 0.74 to 1.53 %, 0.25 to 0.98 % and 0.72 to 1.09 % for Ca, Mg and S respectively and from 5.71 to 31.0 mg kg−1, 7.42 to 12.9 mg kg−1, 33.6 to 58.6 mg kg−1, 82.5 to 681 mg kg−1 and 82.8 to 936 mg kg−1 for B, copper (Cu), zinc (Zn), manganese (Mn) and iron (Fe) respectively. On the basis of DRIS derived sufficiency ranges, 57, 24, 62, 3, 3, 9, 7, 5, and 26 % leaf samples were having less than optimum concentration of N, P, K. Ca, Mg, S, B, Cu and Mn respectively. The optimum ranges developed can be used as a guide for routine diagnostic and advisory purpose for balanced utilization of fertilizers.
Litter decomposition is driven by microbes and is more influenced by litter quality than environmental conditions in oil palm streams with different riparian types
Rapid and extensive conversion of tropical forests into oil palm (Elaeis guineensis) (OP) plantations pose serious threats to tropical stream processes. To mitigate land use change impacts on stream ecosystems, retention of riparian vegetation is typically proposed. We evaluated the effectiveness of a gradient of riparian qualities in oil palm streams: (1) natural forest; (2) OP-native forested buffer; (3) OP-native understory, no chemical input (OPOP) and (4) OP-no buffer, to mitigate impacts on in-stream litter processing. Leaf bag method entry using two leaf species of contrasting litter quality (Macaranga tanarius and OP) were deployed into streams. Across all riparian types, microbes were the main drivers of decomposition with negligible macroinvertebrate shredding activities. Leaf decomposition rates were more influenced by litter quality than changes in environmental conditions in the different riparian types. Across all sites, native Macaranga litter decomposed approximately 5× faster than OP litter possibly due to high structural compounds in OP leaves. Macaranga litter was also more susceptible to changes in environmental conditions as leaf decomposition positively correlated to phosphorus and potassium content. However, OP leaves were resilient to stream environmental changes and decomposed slower only at OPOP sites. These varying responses reveal complex interactions within tropical stream ecosystems. We suggest that riparian management strategies as well as plans to restore functioning in degraded tropical streams should ensure a wide diversity of native riparian tree species in order to effectively mitigate adverse OP plantation impacts on tropical stream functioning.
Evaluation of Lapping Grains based on Shape Characteristics.
The shape and size of abrasive grains during lapping varies complicately and irregularly. In this study, the aspect ratio of grain size and the fractal dimension of the grain external form were used as shape characteristics of grain in order to evaluate grains with lapping time. The results obtained are summarized as follows : (1)The fractal dimension increases due to microscopic fracture and decreases due to macroscopic fracture or attritious wear. (2)The aspect ratio and the fractal dimension, which are grain shape characteristicsis of the macroscopic shape and the microscopic surface complication of grain respectively, can be used for evaluating grain shape variation during lapping.