The effect of fertiliser P on crop biomass production, partitioning, and quality in 'Challenger' sweet corn

Abstract

Sweet corn kernel yield responds to phosphorous (P) supply, but whether the response is mediated through a general increase in crop biomass or increased partitioning to kernels is unclear. Furthermore, changes in ear quality (ear length, diameter, and unfilled tip length) may also result from changes in crop biomass or partitioning. This research quantifies the partitioning between vegetative and reproductive (including ear quality) components for field-grown sweet corn crops, with a range of total biomass yield resulting from different rates of P fertiliser. To do this, ‘Challenger’ sweet corn was sown in 2 consecutive seasons (2001–02 and 2002–03) on a low-P site (Olsen P = 6.5 μg/g) at Lincoln, Canterbury, New Zealand. Five rates of P fertiliser were applied in each season. In 2001–02, 0, 50, 100, 150, or 200 kg P/ha was applied. These were followed by an additional 0, 0, 10, 20, and 40 kg P/ha in 2002–03. This gave a fertiliser range of 0–240 kg P/ha over 2 years. The resulting range in crop biomass (9.7–16.7 t DM/ha) was conservatively partitioned to vegetative (45%), rachis and husk leaf (32%), and kernel (23%) fractions, indicating that kernel yield responses were solely related to changes in crop biomass. The number of harvestable ears increased by 0.39 ears/m2 for every 1 t DM/ha increase in crop biomass. Similarly, ear quality was related to the kernel yield per primary ear. Specifically, the unfilled tip length decreased by 3.1 mm and individual kernel dry mass increased by 16 mg for every 10 g increase in kernel DM per ear. These results show that P fertiliser should be applied at optimum rates (in these experiments ≥100 kg P/ha) to maximise sweet corn crop biomass, which in turn will lead to maximum kernel yield and ear quality. The conservative partitioning of crop biomass suggests that other agronomic factors that increase total biomass production are likely to have a similar effect on crop yields.