Weed Biomass and Weed Species Diversity of Juvenile Citrus Trees Intercrop with some Arable Crops

A preliminary study was carried out to evaluate the performances of eight crops in the intercrop of citrus with arable crops at the National Horticultural Research Institute (NIHORT) Ibadan, Nigeria. Eight arable crops: maize, cucumber, sweet potato, Corchorus olitorius, large green, grain amaranth, Mucuna pruriens var. utilis, and groundnut were intercropped with young citrus trees in the early planting season of 2010 with sole citrus as control. The experiment was laid out in a completely randomized block design with three replicates. Data were collected on weed flora, weed density and weed dry weight. Results showed that the relative frequencies of weeds in all the plots were less than 4% at both 6 and 9WAP. Gomphrena celosoides, Oldenlandia corymbosa and Tridax procumbens were most preponderant in appearing in all the plots. Tridax procumbens had a consistent relative frequency (2.34%) in all the plots except in citrus/maize plot (0.78%) at 9 WAP. Significantly lower broadleaf weed densities were obtained in citrus/sweet potato, citrus/large green, control plot and citrus/cucumber (28.67, 45.00, 50.00 and 76.33 m-2 respectively) than in citrus/groundnut plot (143.00 m-2). Similarly, significantly lower grass weed densities were produced in citrus/Mucuna and citrus/sweet potato (0.33 m-2 each) plots than the control plot (11.33 m-2). Whereas citrus/corchorus plot produced significantly lower broadleaf weed dry weight (37.59 g m-2) than citrus/Mucuna plot (126.47 g m-2) at 3WAP, citrus/large green plot (16.15 g m-2) and citrus/groundnut plot (123.25 g m-2) followed the same trend at 6 WAP. Sedges dry weights were less than 7 g m-2 in all the plots compared with control plot.