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Mangrove forests are globally distributed, including Nigeria with the third largest mangrove area in the world. Mangroves perform diverse ecological and productive functions wherever they exist. They are considered to be the most efficient ecosystem in carbon synthesis on Earth. But the nature of their habitat with features of both terrestrial and aquatic environments imposes on them certain challenges that are management-oriented, such as reclamation as practiced in some countries. The agricultural use of mangrove swamps requires thorough understanding of their peculiarities and potential in productive systems, as well as adaptability of crops that can be grown, all of which result from research data in specific localities across the globe. Physical and chemical properties of three soil units or sites in their natural setting in the mangrove (Rhizophora spp.) forest area of Ogonokom-Abua, Rivers State, Nigeria, were determined and then evaluated relative to benchmark fertility criteria. This was to provide an insight into their expected impact on plant growth and, hence, their potential for sugarcane cultivation. The data from laboratory soil analyses showed varying degrees of limitations, including the generally coarse or sandy (63–75% sand) textures with predisposition to poor soil-air-water relations and plant nutrient deficiencies in intensive agricultural production. Soil unit or site I in uplifted or reclaimed platform that is no longer subject to flooding by saline tidewater appears to have moderate prospect in agricultural production. Nutrient status, though low coupled with severe acidity (pH 4.8) and salinity (20.0dSm−1), soil unit/site I can be improved upon with appropriate management practices for sustainable sugarcane production in the study area and similar environments in the Niger Delta. Soils of units II and III which are prone to recurrent flooding can only be cultivated to naturally adaptive crop species that will also withstand or tolerate extreme levels of salt stress or salinity (21.0–36.5dSm−1), sodium and aluminium toxicities (11.59–12.75 ESP and 20.73–38.10% Al-sat., respectively) and, particularly, waterlogging. Differences in soil properties were substantially reflected in growth performance of sugarcane crop in the study area. In soil unit or site I, the plants produced higher cumulative average number of tillers, nodes and green leaves than the overall average and achieved mean stalk length, stalk girth, leaf length, leaf width and leaf sheath length that exceeded the 3-monthly average values at 3, 6, 9 and 12 months after transplanting (MAT). Growth indices of the plants in soil unit III were the least, while those in unit II were midway between units I and III. Furthermore, soil unit I was significantly different from unit II in leaf width and leaf sheath length as well as from unit III in stalk length, stalk girth, number of nodes, internode length, number of green leaves, leaf length, leaf width and leaf sheath length. Soil unit II was also significantly different from unit III in stalk girth, number of nodes and green leaves, leaf length and leaf sheath length. Thus, there is no gainsaying about the progressive deterioration in soil conditions with the attendant reduction in growth of the crop from sites I to III. Except for soil unit I that is fairly fertile and can be cultivated to sugarcane crop but at great costs in managing soil acidity, salinity and nutrient deficiency challenges, especially potassium, soil units II and III are only marginally fertile and should better be preserved to perform other vital ecological roles rather than their instant use for agricultural production. However, in the event that soil site II is reclaimed and prevented from recurrent flooding by saline tidewater in the area, together with unit I, and given proper management, these sites would provide extensive land area in the mangrove belt for mechanized sugarcane cultivation at commercial scales to boost the sugar industry in Nigeria. An integrated multidisciplinary policy framework, pragmatic and collaborative implementation strategies and suitable management practices for sugarcane cultivation are all that are needed to assure sustainable socio-economic human development in the region. |
