Land Suitability Assessment For Lowland Rice (Oryza Sativa) Cultivation On Three Selected wetland soils in plateau state, nigeria

Abstract

Wetland soils represent vital natural resources that are grossly underutilized for agriculture, due mostly to paucity of reliable data. Their high potential for use in intensive rice cultivation has not been fully exploited, and to increase rice production, intensified use of the wetlands is inevitable. The need for increase rice production to feed the country’s teeming population and to reduce the dependence on imported rice informed the initiation of this study on land Suitability Assessment for Lowland Rice (Oryza sativa) cultivation in Plateau State.The study involved three aspects: (i) soil characterization and classification (ii) land suitability assessment, in which land qualities were related to agricultural requirements of rice, and (iii) field trials using rice performance to ascertain the productivity of the sites. Three wetland soils in Plateau state were selected: a site at Shendam in the Shendam Local Government Area (LGA), another in Ganawuri in Riyom (LGA), and a third at Kuru in the Jos South (LGA). Climate data were collected from Nigerian Meteorological Services at Jos Airport and Pankshin. Field procedures commenced with free survey to determine the extent of the wetland soils. Soil auger was used to examine the soils and 50, 30 and 20 auger samples were studied at Ganawuri, Shendam and Kuru sites respectively. Two profile pits were dug in each site and the following morphological and physical features were studied. These included colour, texture, mottles, clay skins and pores. Data were recorded on a field soil description proforma.Samples were collected from the horizons for the determination of particle size distribution and for chemical analysis.The soils of the three sites were generally clayey but the soils of Shendam site had comparatively a higher proportion of sand (508 gkg-1) when compared to Kuru (390 gkg-1) and Ganawuri (260 gkg-1). Clay increased with depth at the three sites. Evident in these soils were low native soil fertility levels, such as total nitrogen (0.10 – 0.15%), ECEC (7.94 – 12.03 cmolkg-1), and organic matter content with values of 0.87%, 1.01% and 0.96% for Shendam, Ganawuri and Kuru respectively. Aided by the morphological, physical, chemical and climate data, and based on their high base saturation, subsoil clay accumulation and aquic soil moisture regime, the soils were classified at the subgroup categoric level of the Soil Taxonomy as: Typic Endoaqualfs, Aquic Kandiustalfs and Aquic Arenic Kandiustalfs; and correlated with World Soil Reference Base (WRB) as Gleyic Luvisols, Gleyic Lixisols and Gleyic Lixisols, for Ganawuri, Kuru and Shendam respectively. The soils were also classified using the Fertility Capability Classification as: Cdgh for Ganawuri site, and Lgdkh for both Shendam and Kuru sites (Where: L=Loamy texture, C= Clayey texture; and modifiers: g=aquic moisture regime, d=dry season that leaves topsoil dry for longer than 3 months, k=soil falls into Kaolinitic mineralogical family, h=pH between 5.0 and 6.0 (H2O) indicates a good environment for rice growth).The land qualities were first ranked and matched with the crop requirements to arrive at individual ratings of the land characteristics, which were then used as inputs in the parametric methods to obtain the final land index (i.e. the suitability classes of the pedons). For the land suitability assessment for rice production the three soils were classified currently, as marginally suitable (S3), while potentially Ganawuri was moderately suitable (S2), and marginally suitable (S3) for Kuru and Shendam. In authenticating the suitability classifications, field trials using three rice varieties (FARO 44, WITA 4 and FARO 35) were carried out at the three sites for two planting seasons: 2011 and 2012. The results showed that Ganawuri site produced the highest and best economic yield of 4.45 t/ha, followed by Kuru site, 3.7 t/ha and the Shendam site, 3.3 t/ha. For the two years and from the three sites, FARO 44 gave the highest grain yield of 4.2 t/ha followed by WITA 4 (3.74 t/ha) and then FARO 35 (3.71 t/ha).Gross margin analytical model: GM=TR-TVC was used to ascertain the profitability of growing rice at the sites by comparing the cost of inputswith the economic benefit realized. It was observed that the gross returns of rice production per hectare of the three wetland sites gave a benefit cost ratio (BCR) of 1.80, 1.54 and 1.54 for Ganawuri, Kuru and Shendam respectively. In the case of Ganawuri, for instance, this simply means that for every N1 (one naira) invested in rice production, a return of N1.80K (one naira seventy nine kobo) was obtained, meaning a profit of N0.80K per naira on investments. This study has revealed that the three wetland sites are suitable for profitable rice cultivation given the suitable climate, wetness, topography and physical properties condition of the soil. However, there are nutrient deficiency problems especially nitrogen that need to be ameliorated with appropriate levels of organic matter and nitrogen fertilizers