Influence of time of application on the utilization of nitrogen fertilizer by asparagus, estimated using 15N

Abstract

The effect of nitrogen (N) fertilizer on the production of a 6-year-old asparagus (Asparagus officinalis L.) crop was examined over 2 years by the application of 0, 50 or 100 kg N ha-1 as ammonium sulphate at three times; 1) prior to fern growth (9 months before harvest), 2) prior to harvest, or 3) early-harvest prior to the main period of spear production. The utilization of N fertilizer was examined by applying 15N-enriched ammonium sulphate to 2 m × 2.5 m microplots within the 50 kg N ha -1 treatments.There was a 12% response in spear production to added N in the first harvest year only and there was no significant effect of rate or time of N application. Plant uptake of added 15N by the end of the first harvest period was 25, 11 and 4% of the total applied for the pre-fern, pre-harvest and early-harvest treatments respectively. About 60% of the 15N applied pre-or early-harvest remained in the soil at the end of the first harvest period. Most of the ~SN in soil in the pre-harvest treatment occurred as inorganic N and had been leached into the 150-600 mm soil depth. In contrast, most of the 15N that remained in soil from the early-harvest application was in the 0-75 mm depth and 40% of this had been immobilized into organic N.In the short-term (less than one year), utilisation of 15N-labelled N fertilizer by asparagus was greatest when applied prior to fern growth. However, after 2 years there was no difference between treatments in ~SN recovery in plant or soil. Thus, time of application of N fertilizer had no long-term effect on production or utilization of N fertilizer by asparagus.

Life Cycle Assessment Based Evaluation of Regional Impacts from Agricultural Production at the Peruvian Coast

“…In contrast, the leached fraction of N applied was estimated to be small for mandarins, avocados, asparagus, and apples, mainly due to permanent soil cover and the lack of tillage. Ledgard et al have also shown that more than 60% of the N applied to asparagus remained in the soil at the end of the harvest period. Nevertheless, amounts of residual nitrate in the soil are high for all the perennial fruits and represent a significant leaching potential from the sandy soils in the project region…”