Development, classification and rainfed paddy soils potency derived from lacustrine materials in Paguyaman, Gorontalo

Abstract

Efforts to increase and develop paddy soil other than irrigated paddy soil (IPS) are essential in order to improve rice production. Rainfed paddy soil (RPS) is the second granary national after IPS, although current productivity of RPS is low and it has complex limiting factor. The objective of this research were: (1) to study the development of RPS based on soil characteristics and genesis, (2) to identify the main factors influencing the formation of soil profiles, (3) to classify the soil according to Soil Taxonomy classification system, and (4) to evaluate land potency for rice and corn. The research was carried out on 9 pedons from lacustrine materials on E4 agroclimate zones. RPS and upland (UL) pedons are located in Sidomukti of Gorontalo Regency and Molombulahe of Boalemo Regency. While, the IPS pedon are Bandungrejo of Gorontalo Regency. Field observations were done throughout toposequent transect on the lower, middle and upper slope position. Soil samples taken from each horizon of each pedon for laboratory analysis. The observed parameters were morphological characteristics, physical, chemical and mineralogical properties of the soil. The data were analyzed with quantitative and qualitative analysis. Soils were classified based on Soil Taxonomy system, whereas land potentials were evaluate by land suitability analysis with the parametric approach. Land suitability classes (LSC) were determined by Square Root Land Index Method. The results of this study showed that all pedons have B horizon but IPS is more developed than the RPS and the UL. The IPS pedon is more weathered intensively than the RPS and the UL. The main genesis process in all pedon were eluviation, illuviation, lessivage, pedoturbation, braunification and gleization, except for UL pedon from Molombulahe that do not reflact gleization process. The main factors of soil formation were climate, age (time), topography and human activity. The soil classification of PNS1, PNM1 and PNM2 pedon were classified as Ustic Endoaquert, fine, smectitic, isohypertermic; PNS2 pedon classified as Vertic Endoaquept, fine, smectitic, isohypertermic; PNS3 pedon classified as Vertic Epiaquept, fine, smectitic, isohypertermic; PNS-LK pedon classified as Typic Eutrudept, fine loam, smectitic, isohypertermic; PNB pedon classified as Ustic Epiaquert, fine, mixed, active, isohypertermic; PNM3 pedon classified as Aeric Epiaquept, fine, smectitic, isohypertermic; and PNM-LK pedon classified as Typic Eutrudept, fine, smectitic, isohypertermic. The highest LSC of land utilization types (LUT) for local paddy was highly suitable (S1), while the lowest one was not suitable (Nna). The highest LCS of paddy-corn and paddy-corn-corn LUTs was marginally suitable with nutrient availability and water as a limiting factor (S3na and S3wa), while the lowest LSC was not suitable cause same limiting factors (Nna and Nwa). The potency of RPS similar to potency of IPS. The full recommendation of LUT were LUT of local paddy with B (100% of recommended dosage) and C pattern (prescription dosage), except for Inceptisol from Molombulahe consist of local paddy LUT to A (none fertilizing), B and C pattern. The Other LUTs were including requiring recommended and not recommended.