In my observations, Sabrex performance is affected by several factors:  Soil type, hybrid root strength, hybrid relative maturity, fertilizer management, water availability, and disease pressure.

Soil type:  the lighter the soil, the more likely you are to see a yield increase.  I have seen yield increases in black soils, but the bump is due to one or more of the other factors.

Hybrid root strength:  hybrids with weaker root systems respond to Sabrex.  Sabrex increases root mass and stalk diameter and enables these hybrids to uptake more nutrients, especially when disease pressure is higher.

Hybrid maturity:  shorter season hybrids show more responce to Sabrex because their "window of opportunity" for peak yield is smaller.  Again, I have seen it work well in long season hybrids too, but it is due to one of the other factors.

Fertilizer management:  Sabrex helps scavange nutrients and therefore will show more response when nutrients are normally placed farther away (broadcast fertilizer or manure) than compared to banding nutrients close to the row.

Water availablitity:  Drought during critical times (pollination or grain fill) can limit yields if the roots cannot access enough water.  If water is abundant during these times, then Sabrex won't boost yield unless other factors come into play.

Disease pressure:  Corn on corn  and heavy manure applications will elevate fungal diseases of both the leaves and roots.  Fungicides like Headline can help with the leaves, while Sabrex can help with the roots.

Sabrex is not a cure all.  Occasionally, it will actually reduce yield due to the fact that root growth can take away energy from grain fill when all other stresses are low.   The graph below shows three years of data on Sabrex and yes it does show  an occasional yield reduction.  But overall the yield average is very positive.  A plot on your own farm will determine if the hybrids and the management that you are using will be a good match for Sabrex.

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