Nitrogen uptake and partitioning under alternate- and every-furrow irrigation

Alternate-furrow irrigation, combined with fertilizer placement in the non- irrigated furrow, has the potential to reduce fertilizer leaching in irriga ted corn (Zea mays L.). The potential also exists, however, for reduced N u ptake under alternate-furrow irrigation. This study examined the effects of fertilizer placement and irrigation treatment on N uptake, root --> shoot --> root circulation, and partitioning between reproductive and vegetative tissues. Rainfall was above average in both years of the study, especially during May and June, so that root growth beneath the non-irrigated furrow w as equal to root production beneath the irrigated furrow. Under those condi tions, soil NO3 concentration in the fertilized furrow during late-vegetati ve and reproductive growth was greater in the alternate-furrow compared wit h the every-furrow treatment, resulting in increased fertilizer N uptake du ring reproductive growth and increased N partitioning to reproductive tissu es under alternate-furrow irrigation. About 80% of the fertilizer N found i n roots had first been translocated to the shoot and then returned via the phloem to the root system. Nitrogen cycling from root to shoot to root was not affected by irrigation treatment. Alternate-furrow irrigation successfu lly increased N uptake and reduced the potential for NO3 leaching when envi ronmental conditions allowed adequate root development in the non-irrigated furrow, and when the growing season was long enough to allow the crop to r each physiological maturity.