1. CHEMICAL PROPERTIES OF PEAT SOILS UNDER PINEAPPLE CULTIVATION
1Nur Qursyna Boll Kassim, 1Adzmi Yaacob 2Zaini Hamzah and 1Abdul Rashid Ahmad
1Faculty of Plantation and Agrotechnology, Universiti Teknologi MARA, Shah Alam
2Faculty of Applied Sciences, Universiti Teknologi MARA, Shah Alam
INTRODUCTION
Study on the changes in soil chemical properties of peat soils is still lacking especially for pineapple-cultivation in Malaysia. Peat soils are formed from the accumulation of organic matter in a condition where the plant matter production is greater than its rate of decomposition due to either low temperature, waterlogged condition or extreme acidity (Driessen, 2001). In tropical peat soils, the amount of nutrient transported was largely affected by water table, pH, seasonal changes, degree of decomposition and nutrient adsorption capacity (Andriesse, 1988; Richardson and Paul, 1986). At different depth, concentration of nutrients differs and high rainfall makes them prone to leaching (Zaharah et al., 2004). Due to the existence of large areas of peat soils in Malaysia, there is a need to manage these soils in sustainable way for continuous crop production. This study look at how the chemical properties of peat soil is affected by pineapple cultivation activity.
OBJECTIVE
To characterize selected chemical properties of peat soil under pineapple crop.
MATERIALS AND METHODS
The sampling area was located at Klang, Selangor (Grid reference: N02°57’, E101°30’). The area was classified to have a moderate to deep, ombrogenous and oligotrophic peat soils. Samples were taken at natural peat (P1), 3 years pineapple-cultivated peat (P2) and 4 years pineapple-cultivated peat (P3) plots, at two different depths (0-25 cm, cm), with 6 sampling points for each plot and being replicated three times. Samples were then oven-dried and undergo the sieves (60 mesh) for further analysis. Soil pH and conductivity were determined by using pH meter and conductivity meter respectively, with a 1:5 ratios (sample: water). Soil K, Na, Mg and Ca were determined by using a leaching method, where the sample extractions were further analyzed with steam-distillation method for CEC; exchangeable K, Na, Mg and Ca were analyzed by using Atomic Absorption Spectrophotometer (AAS). Kjeldahl-method was used to determine total N (Jones, 2001); total C was determined by using Walkley & Blacks rapid titration method and total P was determined using Aqua Regia and Blue method (Bray and Kurtz, 1945). All gathered data were statistically analyzed using SPSS.
RESULTS AND DISCUSSIONS
Reference:
P1: Natural peat soils
P2: 3 years pineapple-cultivated peat
P3: 4 years pineapple-cultivated peat
Figure 1:Selected chemical properties in pineapple-cultivated and non-cultivated tropical peat soils at different depth
The peat samples were acidic with pH that ranged from 3.24 to 3.41 indicating the soil solution chemistry is controlled mainly by the activity of Al and Fe (acid cations). Increased of pH in the pineapple cultivated plot is due to incorporation of lime. The conductivity was significantly reduced after 4 years of pineapple-cultivation due mainly to the drainage system constructed that removed much of the salt suspected of coming from nearby sea water incursion. This was also reflected in the significant reduction of Na in the cultivated plots. Increased in total N could have resulted from N fertilization. Rapid decline in total C after cultivation is due to continuous decomposition of peat due to drainage and some tillage. Greater total C in the deeper layer indicate lesser decomposition at depth due the influence of water table and this was also reflected by the C:N ratio that was reduced in the cultivated plot where decomposition rate is greater. Contrasting pattern shown after 4 years of cultivation (P3) on surface peat indicate higher decomposition rate is occurring here. The significant relationship between total N, total C and C/N ratio was supported by the correlation data shown in Table 1 and Table 2. Similar pattern was observed in peat depth of 25-50cm. The increase of Ca concentration was most likely due to the liming activity upon cultivation which also lead to higher decomposition rate as reflected by correlation between Ca, total N and C/N ratio. As lime being added, the pH increased and this lead to high microbial-decomposition activity, which further contributed towards increment of total N and lowering of C/N ratio. The correlation of Ca with available P is possibly due to extra positive charges of Ca2+ which was available in the sampled peat, ready to fix negatively charged H2PO4-. Results indicate the importance of liming with Ca to improve soil pH. The decreasing trend of Mg, K and P concentration could be due to rapid uptake by the pineapple crop, but K could also be leach by drainage due to its high mobility in the soil solution. The correlation between K, Na and conductivity indicated that both were rapidly leached from the system due to their high solubility and mobility. For the non-acid exchangeable cations (Ca, Mg, Na and K), they are significantly correlated with each other at both depths except Ca (shown in Table 1 and Table 2). CEC showed little changes regardless of depth. The very low total concentration of bases (Ca, Mg, Na and K) indicate that the exchangeable sites in peat is dominated by acidic cations (H+, Al3+, and Fe2+) and liming is necessary to reduce their acidic effect.
Table 1: Correlation of selected chemical properties in pineapple-cultivated and non-cultivated tropical peat soils at a depth of 0-25cm
Table 2: Correlation of selected chemical properties in pineapple-cultivated and non-cultivated tropical peat soils at a depth of cm
CONCLUSIONS
Peat is naturally very acidic ( pH3-pH4) and the soil solution chemistry is controlled by the activity of acid cations (H+, Al3+ and Fe3+). Upon drainage and cultivation, sampled peat was oxidized and pH was improved through liming resulting in rapid microbial-decomposition which further increases mineralization process that lasts for 3 years (shown by total N, total C and C/N ratio). CEC was dominated acid cations by Ca for non-acid cations. Ca and Mg may take part in the fixation of available P and reduced available P in the peat. It can be concluded that the chemical properties of tropical peat soils studied undergo alteration and behave differently from its natural state after certain years of pineapple-cultivation due mainly to the effect of drainage and liming.
REFERENCES
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Driessen, P.M. (2001). Histosols. Lecture notes on the major soils of the world, Rome. 94:
Jones, J. Benton. (2001). Laboratory guide for conducting soil tests and plant analysis. Pg 27 – 41; 62 – 79.
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Zaharah, A.R., Adebiyi, O.V., Jalloh, M., Hassan, M.H. and Yusop, S. (2004). Fertilizer nutrient studies on Malaysian peat and the implications for their management. Proc. Soils 2004 Conference, April Penang, Malaysia.