Uptake of lead by futed pumpkin (Telfairia occidentalis Hook F.) in an ultisol

Abstract

Pot and field trials were conducted at the Faculty of Agriculture, University of Benin to determine the influence of Pb on some agronomic characters of Telfairia occidentalis and some chemical properties of soil. Completely randomized and randomized completely block designs were used in greenhouse and field trials respectively. In the greenhouse trial, lead nitrate (Pb(N0 3 ) 2 ) was applied at rates of 0, 50, 100 and 200 mg per 5 kg sieved and air-dried soil obtained from a depth of 0-15 cm. The pot rates equivalent to 0, 20, 40 and 80 kgha -1 were used in the field trial. Results indicated that the soil used was texturally sandy loam and an ultisol as demonstrated by its low base saturation. The pH, organic carbon, Effective Cation Exchange Capacity (ECEC), Exchangeable acidity, N, K, Mg, Ca, Na, Fe, Mn, Zn, free Fe and Al oxides, Amorphous Fe and Al oxides content of the soil decreased inconsistently. The organic carbon however increased in the field while the available P appreciated in the entire trials. The Pb content of the soil increased with the levels of Pb treatments when compared with the control throughout the trials. The N, P, K, Mg, Ca, Na, Fe, Mn and Zn content of shoot and root as well as their uptake also decreased consistently with increasing Pb treatments. In addition, the Pb content as well as uptake by the shoot and root also increased consistently with increased rates of the Pb applied in the trials with the minimum levels of the Pb content and uptake recorded at the control treatments. The crude protein content decreased with increased heavy metal treatments in both root and shoot with the control having the highest crude protein content. The highest crude protein percentage was recorded in the shoot compared to the root. A decrease in the dry matter yield with increased Pb treatments in shoot and root was recorded in the trials. Results also showed that the Pb influenced the height, collar girth, leaf area and number of leaves with control treatments higher than other treatments at final harvest. The manifestation of anthocyanin pigmentation in 200 mg Pb and 80 kg Pb ha -1 treatments revealed the negative influence of the Pb on the phosphorus uptake by Telfaria occidentalis.