Abstract:In the trials, Cassava mill Effluent was used for fluted pumpkin (Telfairia occidentalis) cultivation in order to verify the influence of the effluent on the growth and some soil chemical properties. In this regard, a completely randomized and randomized complete block designs were used in the greenhouse and field trials respectively with 6 treatments replicated 3 times. In the greenhouse, the following rates of 0, 100, 200, 300, 400 and 500 ml per 5 kg topsoil were used while in the field trial, 0, 40000, 80000, 120000, 160000 and 200000 litres/ha were utilized. The rates used in the field were equivalent to those of greenhouse. In both trials, the cassava mill effluent was applied 2 weeks prior to transplanting the seedlings. Results indicated that the cassava mill effluent significantly (P < 0.05) increased soil pH, organic carbon, N, P, K, Ca, Mg, Na, Fe, Cu and Zn whereas the exchangeable acidity decreased significantly (P < 0.05) with corresponding increase in cassava mill effluent treatments. Except N and Na, which declined with corresponding increase in the cassava mill effluent treatments, an improved P, K, Mg, Ca, Fe, Cu and Zn components was achieved in cassava mill effluent polluted plants compared to control. The plant height, significantly (P < 0.05) decreased with increased cassava mill effluent treatment in the greenhouse trial while in the field trial, 120000 litres/ha was significantly (P < 0.05) higher than other treatments. In the greenhouse trial, significantly (P < 0.05) higher number of leaves was attained in 100 ml treatment compared to other treatments whereas in the field trial, the 120000 and 200000 litres/ha were significantly (P < 0.05) higher compared to other treatments

A nursery trial was conducted in the screen house of the Teaching and Research Farm, Faculty of Agriculture, University of Benin, Benin City, Nigeria in 2011 to investigate the effect of different potting media and watering frequencies on the growth of Dennetia tripetala seedlings. Three different growing media: Rice husks (Rh), pig dung (Pd) and cocoa husk (Ch) were used as sources of growth. They were combined in a 1:1 ratio to make seven media combinations with four watering frequencies at once daily (D 1 ), twice daily (D 2 ), once every other day (D 3 ) and twice every other day (D 4 ). The trial was laid out in a 7 x 4 factorial design fitted into a Completely Randomized Design (CRD) with three replications. Data were collected on plant height, leaf number, and canopy diameter, stem girth, dry weight of root and shoot. Results obtained revealed that potting medium with sole pig dung significantly produced the best seedling attributes in terms of plant height (11.46cm), stem girth (1.01cm), canopy diameter (9.58cm) while, leaf number (11.16), dry weight of shoots (0.51g) and roots (0.19g) were best with sole rice husk and rice husk plus pig dung (1:1) respectively. Watering twice every other day had a significant (p<0.05) influence on plant height, canopy diameter, stem girth and root dry matter. There were significant interaction effects between sole pig dung and watering once, twice daily and twice every other. However, in order to save labour, money and time spent in watering, watering twice every other day plus pig dung sole may be adequate for raising D. tripelata seedlings.

A preliminary pot trial was conducted in a greenhouse to determine the effects of rubber effluent on some soil chemical properties as well as early growth and nutrient uptake by maize plant. The levels of rubber effluent used were 0, 50, 100, 150, 200, 250 ml per 2 kg soil. The trial was arranged in a completely randomized design and replicated three times. Results showed that the soil pH, organic carbon, N, P, K, Mg, Ca Na, ECEC, Fe, Mn and Zn were significantly higher (P<0.05) in rubber effluent treated soils than the control, while the control was significantly higher in exchangeable acidity. Except Zn, the N, P, K, Mg, Ca, Na, Fe, Mn content and their uptake by the plant were significantly higher (P<0.05) in rubber effluent treated plant than the control. The plant height, leaf area and number of leaves were also significantly higher in effluent treated plants than the control. The N, P, K, Mg, Ca, Na content and their uptake and the growth parameters however declined at 200 ml treatment while in Fe, Mn and Zn content and their uptake, there was no definite pattern of increase with increasing effluent levels. Conclusively, rubber effluent contained vital plant nutrients which may be favorable to soil fertility improvement and maize growth at the application rates.

This review revealed that heavy metals are naturally components of the soil orchestrated by weathering processes and that the abundance of these metals in our soil environment nowadays is due to numerous anthropogenic activities. These heavy metals are in two major categories namely the essential and non-essential ones. The essential heavy metals are needed in trace amount by living things for their physiological processes. But at higher concentration, it is hazardous in plants and animals. On the other hand, the non essential ones are dangerous to plants and animals even at low concentrations. This write-up further showed that soil pH, organic carbon, available P, oxides, effective cation exchange capacity, moisture content, oxidation-reduction state of the metals, ion exchange and sorption capacity of the metals are some of the soil factors influencing the fate and availability of the heavy metals. At lower levels of these soil factors, heavy metal ions are rendered free in the solution thereby making them available to plant and underground water. However, the most prominent soil factor influencing availability of these metals is the Soil pH. Raising some of these soil factors to appropriate levels have been discovered to reduce the availability of the heavy metals to mankind.

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