Improved In-Furrow Liquid Bradyrhizobium Nodulation Vs. Seed-Applied Treatments for Texas High Plains Soybean.

In general liquid inoculants deliver higher numbers of N-fixing bacteria to planted crop seed than seedbox powders or in-furrow granular inoculants.  Peanut farmers in the Texas High Plains equip planters to apply liquid inoculant in-furrow—which improves nodulation and yields, but this is not done in soybean production.  The objective is to gauge nodulation and soybean yield due to soybean-specific liquid inoculant (Bradyrhizobium japonicum) applied both on the seed as well as sprayed directly in furrow using a streamjet spray tip.  Field tests were conducted 2008-2011 at Lubbock, TX (Becker Underwood ‘Vault’ and EMD CropBioscience ‘Cell-Tech’), and 2010-2011 at Etter, TX (Cell-Tech) using an RCBD layout comparing seed-applied and in-furrow (water carrier volume ~65 liters/ha) inoculant at the manufacturer’s labeled rates).  Soybean nodulation was assessed at ~90 days for nodules per plant, and plots were harvested with a small plot combine.  At Lubbock on a sandy loam soil per-plant nodulation improved by over six-fold to ~23 nodules per plant using in-furrow application vs. 3 nodules per plant with seed-applied liquid application (1 nodule per plant on controls) though no nodulation was measured in 2009 when the soil remained very dry after planting.  Etter nodulation improved ~50% with in-furrow application.   Yields were significantly higher at Lubbock due to in-furrow application but not at Etter.  Improved nodulation using in-furrow inoculant application suggests producers should consider the cost of applying liquid inoculants in-furrow for soybean in the Texas High Plains.