Hydrogen cyanamide (HyCyn) is a product derived from calcium cyanamide. Three decades ago HyCyn became commercially available as a plant growth regulator. Sprayed on dormant plants, it provides uniform bud-break. This present invention provides repeatable methods for using aqueous HyCyn, and other similar water-soluble low molecular weight cyanamide or nitrile containing compounds, as stand-alone biocides. Qualities include: safer delivery to field settings, fewer environmental impacts and predictable plant growth improvement. HyCyn with its systemic qualities can act as a fertilizer, desiccant, nematicide, fungicide, herbicide, growth regulator and an agent of enzyme inactivation. These biocidal and other effects appear to be a result of double or triple bonds connecting carbon with nitrogen, and therefore it is expected that other water-soluble low molecular weight compounds having carbon-nitrogen double or triple bonds can act similarly. Todays improved irrigation methods will replace soil fumigation in many settings. All its metabolites, properly delivered, make plants grow better.