Dry Soil Reduces Fertilizer Phosphorus and Zinc Diffusion but Not Bioavailability

Dry sowing is a practice used in many semiarid agricultural systems where crops are planted early into dry soil to hasten crop emergence following the first rains of the season. This practice increases water use efficiency by promoting rapid canopy development early in the growing season when soils are warm. The question that arises from this practice is whether the efficacy of fertilizers, which are usually simultaneously placed below the seed at planting, is influenced by being in contact with the dry soil for a period of time before seed germination and crop emergence. Commercial granular and liquid monoammonium phosphate fertilizers enriched with Zn were incubated under dry and wet conditions to test the effects of dry sowing on fertilizer diffusion, lability, and subsequent availability to wheat (Triticum aestivum L. 'Axe') plants in the growth chamber using isotopic techniques. Fertilizer incubated in dry soil tended to have a much greater lability than in wet soil, but diffusion was limited. The restricted diffusion during the incubation did not negatively impact nutrient availability to plants subsequently grown in the growth chamber, however, and simulated dry sowing was not shown to have a detrimental effect on fertilizer efficiency.