Understanding Fertilizer Toxicity Symptom Development through High Resolution Imaging.

Fertilizer bands, commonly used in crop production systems, may have toxic effects on seedlings during plant establishment. High temporal and spatial resolution data sets can be acquired by in-situ imaging of root systems with office scanners (Pan et al. 1998; Hammac et al. 2011). Canola (Brassica napus L.) seeds were placed between the scanner face and the soil. Urea fertilizer was banded 5cm below the canola seeds. Scanned images were collected every 4 hours at a resolution of 5.29 um pixel^-1 (4800 dpi). Symptoms of fertilizer toxicity were quantified using Photoshop and ArcGIS. Symptoms of halted apical growth, pre-mature lateral emergence, root shrinkage, and root browning were recorded. Prior to entering the fertilizer zone the apex of the root systems halted growth. Shortly after the cessation of the apical growth shrinkage of the main root and lateral emergence initiated. Finally discoloration advanced up the primary root. In some cases the newly developed lateral roots survived took over growing down wards, while in others the entire root system and seedling died. These results are in agreement with previous studies looking at fertilizer toxicity (Creamer and Fox 1980). The high time and space resolution presented here allows for the spatiotemporal dynamics of fertilizer dissolution and root toxicity symptoms to be explored. The images collected confirm that deep banding of fertilizers cause root toxicity and seedling death. This information has immediate implications for producers growing canola in a single pass system using deep banded fertilizer placement.