Potato and soil 15N recoveries from different labelled forage root and shoot

Abstract

An improved understanding of the contribution of a preceding forage crop to a subsequent potato crop can improve nitrogen (N) utilization in potato production. This study used two rotation experiments to estimate the N contribution from labelled shoot and root of red clover (RC, Trifolium pratense), timothy (T, Phleum pratense) and a red clover/timothy mixture (M) to a subsequent potato crop using microplots in the field. Forage crops were grown with 14NH414NO3 and 15NH415NO3 (98 atom %). The residue exchange technique was used to compare residue treatments of (i) whole plant labelled; (ii) labelled shoot only; and (iii) labelled root only in Experiment 1, and residue treatments of (i) whole plant labelled; (ii) labelled shoot/unlabelled root; and (iii) labelled root/unlabelled shoot in Experiment 2. Averaged across forage treatments, recoverable root biomass represented 64 and 37% of total forage biomass, and the total 15N recovery from labelled roots was 52 and 62% of the total 15N recovery from shoots, in Experiments 1 and 2, respectively. Therefore, forage roots represented a substantial source of N for the subsequent crop. However, less than 5% of the 15N from crop residues was recovered in the potato vines plus tubers, and most of the 15N was recovered in the soil, regardless of the forage or residue treatments. Potato tuber and vine dry matter was greater for the RC than the T treatment for all residue treatments, a finding attributed to greater potato N accumulation for the RC treatment. It is therefore important to consider the contribution of forage roots when studying N cycling in potato systems. Potato N requirements were satisfied more by soil-derived N rather than from fall incorporated forage residues.

Machine learning and computational chemistry to improve biochar fertilizers: a review

“…Because microbial carbon and nitrogen cycles are fundamentally linked, and soil capacity and nitrogen mineralization in soils are closely correlated, management practices resulting in soil organic carbon losses significantly impact how much nitrogen can be stored in soils. So, crop yield is effectively harmed when soil organic matter is lost (Whittaker et al 2023). The mean recovery of a single application of nitrogen-15 fertilizer in aboveground sections of crops at all locations was reported to be 5.7-7.1% in the five following growing seasons (excluding the crop fertilized with nitrogen-15).…”

“…The mean recovery of a single application of nitrogen-15 fertilizer in aboveground sections of crops at all locations was reported to be 5.7-7.1% in the five following growing seasons (excluding the crop fertilized with nitrogen-15). Therefore, a cropping system's first crop's average nitrogen-15 fertilizer recovery rate was 44% (Whittaker et al 2023), and in the first five harvests, there was an overall recovery of nitrogen-15 fertilizer of around 50%. The remaining 50% of nitrogen-15 fertilizer would contribute to a sizable soil nitrogen pool, some of which may be lost from the cropping system, assuming that nitrogen-15 in roots had diminished by the sixth growing season (Su et al 2018).…”

Use of 15N tracers to study nitrogen flows in agro-ecosystems: transformation, losses and plant uptake

“…Three papers in this special issue used 15 N tracer methods to study those pathways. Whittaker et al (2023) studied the contribution of shoot and root residues from forage crops to the subsequent crop, in their case potato, by use of 15 N enriched residues from different forage plants. In two experiments they showed that less than 5% of the 15 N in residues were recovered in the potato plants, while the majority was recovered in soil.…”