Soil fertility and land suitability assessments of the different abaca growing areas in Leyte, Philippines

This study was conducted to assess the soil fertility status and land suitability of the different abaca growing areas of Leyte. Preliminary investigation has been done to establish relationships between growth parameters and biomass or yield of abaca which was the basis in the actual field sampling. Brief description of the sampling areas, agroclimatic data, and topographic parameters were recorded. Soil sample were collected and analyzed for the different soil fertility indicators such as pH, % OC [organic carbon], available P, exchangeable bases (Ksup+, Casup2+, Mgsup2+, Nasup+), extractable acidity (Alsup3+ and Hsup+), extractable micro-nutrients (Cu, Fe, Mn, Zn), and CEC. These parameters were used in the soil fertility and land suitability assessment of the different sampling areas. The approaches used in the soil fertility assessment include Soil Fertility Index (SFI) and Soil Fertility Capability Classification (FCC). Soil pH, available P, exchangeable K, exchangeable Ca, extractable Cu, extractable Zn and extractable Fe were considered as MSFI [minimum soil fertility indicators] for the different abaca-based production systems. With these indicators, samples collected in Cagang, Polahongan, Mahaplag (site no. 13) was found to be high in soil pH that resulted to high availability of Ca in contrast to the samples collected from Tongonan, Kanangga (site no. 01). Relationship of the identified MSFI's revealed that, available P (exponential), exchangeable K (sigmoidal), soil pH (i.e. quadratic), Ca, Fe, Cu (i.e. Gaussian) and Zn (logistic) follow different patterns with respect to the biomass production of abaca. Integrated scored value of the MSFI's showed that Lower Odiong samples of Javier Leyte (site no. 11) registered the highest SFI value of 8.05 while the lowest SFI was noted in Cabintan sample (site no. 03). FCC analysis suggests that more than three-forths (i.e. 80%) of the sampling areas have sandy soils while the modifiers revealed that acidity ('h') is one of the major constraints for abaca production. Land suitability assessment of the sampling areas revealed that only two sites were highly suitable (Ssub1) for abaca production namely: Danao, Ormoc City (site no. 02) and Odiong, Javier (site no. 11). Areas which are currently not suitable (Nsub1) for abaca production includes Hibunauan, Buruaen (site no. 06), Balinsasayaw, Abuyog (site no. 12), Amguhan, Baybay (site no. 9), and Tongonan, Kanangga (site no. 01). The rest of the sampling areas were considered marginally and moderately suitable for abaca production. Field fertilizer experiment in soils with some limitations (i.e. Visca soil-site no. 7) revealed that fertilization significantly affected the growth performance and biomass production of abaca. N, Psub2Osub5 and Ksub2O application significantly influence the growth and biomass production of abaca.