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The study aims at determining the economic impact of the rubber based cropping system introduced to rubber farmers in Nigeria by Rubber Research Institute of Nigeria under the sponsorship of the Common Fund for Commodity (CFC) project in Nigeria coded CFC-IRSG 21. Thirty three farmers were randomly selected in five states in Nigeria (Edo, Delta, Ogun, Kaduna and Akwa Ibom) using interview schedule. The profitability of rubber based cropping systems on farmers' farms in the five states was determined using gross margin analysis. The study revealed that rubber based cropping systems in the study area were profitable with positive gross margins for all the identified cropping systems in the study area. Furthermore, the study revealed that a gross margin of N178, 000/ha and return on investment of N4.79 was the highest for the two cropping system identified in Edo state. A gross margin of N331, 000/ha and return on investment of N7.76 per Naira was the highest for the three cropping system adopted in Delta state. For the four crop combination in Ogun state, a gross margin of N181,000 and return on investment of N6.32 per Naira was the highest. In Akwa Ibom state, a gross margin of N402, 100 and return on investment of N8.05 per Naira was the highest for the three crop combination. For the four crop combination in Kaduna state, gross margin of N 488,000 was the highest. The study however, concluded that cassava featured more in the intercropped combination and it gave higher gross returns in the rubber based cropping systems in Nigeria compared with other crops across the states.

A two-year (2010 and 2011 cropping seasons) field trial was carried out on a Sandy loam Ultisol in south-eastern Nigeria to evaluate the effect of Poultry manure (PM), Defatted palm kernel cake (DPKC) and their combinations (PM + DPKC) on the yield of sweet potato and soil chemical properties. The experiment was laid-out in a randomised complete block design with the treatments consisting of PM, DPKC, PM + DPKC (1:1 by weight) applied at the rates of 5 and 10 t ha -1 each and a control (no soil amendment).The treatments were replicated four times. A significantly (P ≤ 0.05) higher sweet potato yield performances and improved soil chemical characteristics were recorded from plots that received any of the soil amendments compared to the unamended (control plots). Apart from the combined application of PM and DPKC at the rate of 5 t ha -1 which gave a significantly higher yield values relative to single application of either PM or DPKC at similar rate; the effect of the other treatments at the same rate of application on the crop yield and yield related parameters did not differ significantly. However, plots that had either DPKC alone or in combination with PM gave a significantly higher root:vine yield ratio and commercial harvest index, irrespective of the rate of application. Similarly, combined application of PM and DPKC resulted in a significantly higher soil org. C, available P and exchangeable bases. The crop yield values and soil properties recorded from plots treated with PM + DPKC at the rates of 5 and 10 t ha -1 did not differ significantly, hence combined application of PM and DPKC at the rate of 5 t ha -1 could be considered suitable for sweet potato yield and soil nutrient conservation for sandy loam ultisol of south-eastern Nigeria.

Weed management is amongst the most expensive agronomic practice in immature rubber plantation. Field experiment was conducted during the rainy seasons of 2004 and 2005 at the Rubber Research Institute of Nigeria. The purpose was to assess the impact of some creeping economic vegetable crops (vegetable cowpea-Vigna unguiculata L. Walp. ssp sesquipedallis, Egusi melon-Cucumeropsis manni Naaud., Fluted pumpkin-Telfairia occidentalis Hook. F and Pumpkin-Cucumbita pepo) compared to the conventional cover crop (Centrosema pubescens) on weed flora composition when grown with rubber saplings. The experiment was laid out in a randomized complete block design with four replications. Weed flora comprising of 33 species under 17 plant families was observed across the field. Panicum maximum, Elusine indica, Brachiaria lata and other grass and sedge species dominated in the conventional cover crop plots. While ephemeral weed species like Talinum triangulare, Peporomia pellucida, Acalypha cillata and other broad leave weeds dominated in creeping vegetable crop plots, except the Telfairia plot which had weed flora closely similar to those of the conventional cover crop plots. The weed spectrum, density and dry matter weight were significantly lower in the Curcubita pepo and Cowpea plots compared to the conventional cover crop plots. The effect of the cover crops on the plant height and stem girth did not differ significantly within the first 12 months. Thus, it could be said that with the exception of the Telfairia occidentalis, the creeping vegetable crops could be of importance for the control of noxious weed flora in immature rubber.