Method of phosphorus fertiliser application and row spacing on grain yield of faba bean (Vicia faba L.)

Yield responses of faba bean (Vicia faba L.) cv. Fiord to applications of fertiliser phosphorus (P), as superphosphate, were measured in 2 field experiments. The P was either (i) placed with the seed while sowing at 6 cm depth and also cultivating at 3–4 cm below the seed (drilled P) or (ii) placed 3–4 cm below the seed while sowing at 6 cm depth (banded P). This was done when the seed and fertiliser were placed in rows at either the standard 19 cm apart (current recommendation) or 38 cm apart (makes it easier to sow into the stubble of the previous crop). Yield of dried shoots and seed (grain) increased with increasing amount of P applied (0–30 kg P/ha in experiment 1, 0–45 kg P/ha in experiment 2), but were unaffected by the method of P application or spacing between seed and fertiliser rows. Therefore, (i) up to 45 kg P/ha can be drilled with the seed while sowing faba bean crops (current farmer practice) and (ii) faba bean can be sown and fertilised at 38-cm spacings making it easier to sow into the stubble of the previous crop than the 19-cm spacing currently being practiced.

Effects of Phosphorus Fertility on Competition Between Lettuce (Lactuca sativa) and Spiny Amaranth (Amaranthus spinosus)

Field studies were conducted to determine the influence of phosphorus (P) fertility and method of application (banded versus broadcast) on the competitive interaction of lettuce and spiny amaranth. Weed density significantly affected lettuce head weight and spiny amaranth shoot biomass after 5 wk of interference. Weed density and duration of interference had little or no effect on P content of lettuce tissue. Duration of interference did affect P concentration of spiny amaranth; however, weed density did not Spiny amaranth competition reduced lettuce yield, but P was not the limiting factor. Duration of interference and method of P application interactively affected lettuce head weight; however, only duration of interference affected spiny amaranth biomass. Seven wk of interference caused a decrease in lettuce head weight of 20, 8, and 24% when P was broadcast, banded, or not applied, respectively. Banding of P reduced the negative impact of spiny amaranth on lettuce. Although method of P application influenced the interaction between lettuce and spiny amaranth, interspecific competition between the two species probably was not due to competition for P but some other factor.