There is still very little information on the sources of water absorbed by oil palm plant. This information is very important for water management system in oil palm plantation. Thus, this study was carried out to determine current water sources absorbed by the oil palm roots using oxygen (δ 18O) and deuterium isotopes (δD) techniques. Sketches of oxygen and deuterium isotope were total rainfall, throughfall, runoff, measurement at 5 soil depths (namely: 20 cm, 50 cm, 100 cm, 150 cm, and 200 cm), and oil palm stem. Results of this study showed huge variance in the values of oxygen and deuterium isotope. Based on Least Significant Difference (LSD) test, there was no significant value in the oxygen and deuterium isotope of stem water and others; however, a similar value was obtained at the depths of 0 - 20 cm and 20 - 50 cm with the stem water. This indicated that oil palm absorbed water from 0 - 50 cm depth. This result agreed with the oil palm rooting system, which has verified that the root quarter is the most active root of oil palm.
Stable isotope has been developed as a powerful tool for investigating processes in plant-water relations such as recognizing plant water use and responding to different types of water sources, as well as acquiring better understanding of water utilization processes, water use efficiency, pattern, mechanism, and the ability to adopt in arid environments. Plants have to cope with various water sources such as rainwater, soil water, groundwater, sea water and the mixtures of these. Plant water sources are usually characterized by different isotopic signatures (18O/16O and D/H ratios). At present, the measurement of δD, δ18O compositions of various potential water sources and stem water has become a significant means to identify plant water sources [
The analyses of hydrogen and oxygen stable isotope provide an effective approach for studying root water uptake. Zimmermann et al. [
There are marked differences in the stable fracture due to various water cycles resulting in the distinct difference of δD and δ18O in various water bodies [
Three potential sources of natural water (precipitation, stream, and groundwater) have been found to vary widely in isotopic composition [
The research was conducted in Kabun-Aliantan, Tandun (N: 00˚27, 925', E: 100˚49, 219') in Riau, Indonesia. For this purpose, field observation was carried out on the land with the typic Hapludut soil type that has a clay texture, located at 30 - 70 m above the sea level and flat-undulated physiographically. This research was conducted in a plot area of oil palm plantation measuring 50 m × 50 m which consisted of 32 trees. The selection of the trees in the middle of the plot area included as many as 3 trees of oil palm, patterned equilateral triangle as a medium for stem water sampling.
The stem water sampling was conducted on the stem micro sampler type 1906 DVC. The equipment was installed by inserting it into the stem using the first stem pipe end capillary drill which functions to absorb water from the inner wall of palm trunks. The vacuum soil sampler is operated by absorbing water that utilises a suction pipe at the end of the capillary (
Water sampling was conducted by positioning 5 different depths (20 cm, 50 cm, 100 cm, 150 cm, and 200 cm) around each tree in a circle, with three replications of 1.5 - 2 m from the tree. This water sampling was carried
out nine times for observation. In addition, water sampling was also conducted for the rainfall, through fall and run-off samples. The water samples were then analysed for the deuterium and oxygen isotopes in each sample observation using a laser spectrometry. The measurement of the isotope ratios of 18O and D Laser Spectroscopy used a device equipped with a microprocessor control analyser with a precision stable isotope ratio analysis. This stable isotope ratio was determined according to the relative difference of a heavier isotope to the lighter isotope (which has greater abundance) as 18O/16O or D/H. From the analysis of the deuterium content (δ2H or δD) and oxygen-18 (δ18O), stable isotopes of water molecules were obtained from information on the processes that had been experienced by the sample water as evaporation or mixing process between two sources of water.
The composition tools included LGR DLT-100 or LWIA (Liquid Water Analyser isotopes), comprising the analysis of the laser system and internal computer, a CTC LC-PAL liquid auto sampler, a small membrane vacuum pump, and an air chamber output channel that passes air through a column of Diorite for removal of moisture. The isotope ratio relative was calculated to that of a standard Mean Ocean Water (SMOW) as astandard Dawson [
The oxygen isotope calculation with V-SMOW is as follows:
All data were analysed using the statistical LSD test to compare the contents of deuterium and oxygen isotopes in the oil palm trunk and groundwater at each depth. The analysis of oil palm rooting was carried out at the sites to determine the layer that contains the active palm roots which absorb water sources for growth and development. The method of root sampling was done by making the soil profile with a depth of 0 - 200 cm , where the distance sampling was 2, 50 m from the tree trunk, which was then performed on various soil sampling depths (0 - 20 cm , 20 - 50 cm , 50 - 100 cm , 100 - 150 cm , and 150 - 200 cm ) using a ring of soil samples, where the volume of each soil sample was 20 cm × 20 cm × 20 cm . The weighing of soil samples was performed based on the weight of dry samples. This was then carried out based on the criteria for root classifications (primary, secondary, tertiary and quarter) at any depth.
In
No. | Treatment | Deuterium Concentration (0/00) |
---|---|---|
1 | Water Sampling Rainfall | −53.478 A |
2 | Water Sampling Throughfall | −52.133 A |
3 | Water Sampling Run-Off | −58.722 A |
4 | Water Sampling Stem | −54.633 A |
5 | Water Sampling Depth 20 cm | −53.878 A |
6 | Water Sampling Depth 50 cm | −54.644 A |
7 | Water Sampling Depth 100 cm | −55.789 A |
8 | Water Sampling Depth 150 cm | −55.578 A |
9 | Water Sampling Depth 200 cm | −57.767 A |
water samples (−54.633‰) approximated the deuterium concentration of water samples at 20 cm death with −53.878 ‰ and the deuterium concentration of water samples at 50 cm death with −54.644‰. It can be concluded that the value of the deuterium (δD) ratio in all types of treatment in this research did not provide a significantly different effect, whereby the deuterium data sorting concentrations ranged from highest to lowest. The measurement of δD, δ18O composition of various potential water sources and stem water samples was a significant means to identify plant water sources [
Zimmermann et al. [
From
From
No. | Treatment | Deuterium Concentration (0/00) |
---|---|---|
1 | Water Sampling Rainfall | −7.796 A |
2 | Water Sampling Throughfall | −7.708 A |
3 | Water Sampling Run-Off | −8.067 A |
4 | Water Sampling Stem | −7.334 A |
5 | Water Sampling Depth 20 cm | −7.171 A |
6 | Water Sampling Depth 50 cm | −7.663 A |
7 | Water Sampling Depth 100 cm | −7.682 A |
8 | Water Sampling Depth 150 cm | −7.713 A |
9 | Water Sampling Depth 200 cm | −7.997 A |
Depth (Cm) | Primary | Secondary | Tertiary | Quarter |
---|---|---|---|---|
gr/cm3 | ||||
0 - 20 | 0.0151 | 0.0091 | 0.0065 | 0.1261 |
0.0548 | 0.0166 | 0.0124 | 0.1169 | |
0.0981 | 0.0206 | 0.0164 | 0.1766 | |
Average | 0.0560 | 0.0155 | 0.0118 | 0.1399 |
20 - 50 | 0.0190 | 0.0044 | 0.0020 | 0.0161 |
0.0193 | 0.0035 | 0.0023 | 0.0135 | |
0.0483 | 0.0141 | 0.0055 | 0.0200 | |
Average | 0.0288 | 0.0073 | 0.0033 | 0.0165 |
50 - 100 | 0.0 | 0.0 | 0.0009 | 0.0039 |
0.0 | 0.0028 | 0.0005 | 0.0046 | |
0.0 | 0.0049 | 0.0005 | 0.0055 | |
Average | 0.0000 | 0.0025 | 0.0006 | 0.0047 |
100 - 150 | 0.0 | 0.0 | 0.0020 | 0.0018 |
0.0 | 0.0029 | 0.0004 | 0.0019 | |
0.0014 | 0.0010 | 0.0001 | 0.0025 | |
Average | 0.0005 | 0.0013 | 0.0008 | 0.0020 |
150 - 200 | 0.0 | 0.0 | 0.0004 | 0.0 |
0.0 | 0.0005 | 0.0004 | 0.0 | |
0.0 | 0.0011 | 0.0000 | 0.0 | |
Average | 0.0000 | 0.0005 | 0.0003 | 0.0000 |
The analysis of deuterium (δD) and oxygen isotopes (δ18O) in groundwater and water in oil palm trunks provides information on the dynamics of plant utilization of water resources. Based on the Least Significant Difference (LSD) test, no significant value was found in the deuterium and oxygen isotopes in the stem water samples and other samples. However, similar values were obtained at the depths of 0 - 20 cm and 20 - 50 cm in the stem water. It indicates that oil palm absorbs water from the depth of 0 - 50 cm. This result is in accordance with the system of oil palm rooting, i.e. the root quarter (0 - 50 cm) is the most active root of oil palm that absorbs nutrients, water and oxygen.