Effect of Inoculant Type, Inoculant Placement, Nitrogen, and Bacteria Count on Soybean Langdon, ND. 2002.

 

S. Halley, Langdon Research Extension Center-North Dakota State University, Box 310 Hwy 5 E Langdon, North Dakota 58249

*Corresponding author PH: (701) 256-2582, E-mail: shalley@ndsuext.nodak.edu

 

With the advent of soybeans that mature in a relatively short growing season and inclusion of the Roundup tolerant gene into these short-season varieties, soybeans are being produced on increasingly greater acreages in the northern growing region of North Dakota. Most of the acreages being devoted to soybean in these new regions have never produced the crop before. Research is needed to determine management options that will maximize production in the initial soybean crop season on these fields.

 

A symbiotic bacteria necessary for improved health of the soybean, Bradyrhizobium japonicum, is often not present in the soil or present in such low numbers that yields are not maximized until bacteria populations increase. This study was initiated to evaluate management options that will maximize first year production to the producer;

1. 40 lbs/acre supplemental nitrogen fertilizer.

2. Peat or liquid inoculant type.

3. Inoculum seed placed or soil placed and incorporated one week before planting.

4. Inoculum with differing bacteria counts.

 

A research trial, using a RCB design replicated four times, was initiated on a site testing 56 lb/acre available nitrogen (N) at 0-24 inches. This field of previously raised canola at the Langdon Research Extension Center had never previously produced soybean. Urea was the N source applied at 40 lb N/acre to selected treatments. Inoculum tested included peat based Nitrastik-S, 250 million bacteria cells/gram, and Cell Tech 2000, 2 billion bacteria cells/gram, from LIPHATECH. Soil applied inoculum and/or N were hand broadcast to applicable plots and all plots were incorporated with rototiller on 14 May.  A subsequent incorporation preceded seeding of cultivar �Jim� soybean on 20 May.

 

Nodule numbers/plant were small on N treated plots and untreated and not different. Nitrogen addition reduced nodule diameter and generally reduced test weight.  Nitrogen   and inoculant increased protein compared to untreated. Inoculant bacteria count of 11 million or greater increased nodule count/plant compared to 2 million bacteria level except for peat inoculum treatment applied with seed. Yield increases compared to the untreated were measured when bacteria counts were 11 or 22 million regardless of inoculum source and application of N.