Ohio Corn, Soybeans: How Phosphorus Placement Affects Yield, Water Quality

Phosphorus placement has been discussed as a 4R Best Management Practice that results in lower nutrient losses than when P is surface applied and left on the surface. The concept is that by mixing granular fertilizer with the soil, we expose the nutrient to more soil surface area for attachment.

A replicated trial was established at the Northwest Agricultural Research Station-OARDC located near Custer, OH to measure water quality and crop yield with four fertilizer placement options.

Four phosphorus fertilizer treatments are being used:

  1. Surf – Broadcast surface application in fall
  2. 2”x2” – 2 by 2 placement at spring planting
  3. Deep – Deep banding using strip till unit in fall
  4. Incorp – Surface application with disk incorporation in fall

Corn and soybean are planted on 50% of the plot each year. The rate of phosphorus applied for fall treatments is 128 pounds P2O5 applied after the soybean crop and 64 pounds P2O5 in the 2 by 2 placement to both corn and soybean. Fertilizer treatment were applied in fall of 2018/spring 2019.

The STP level is 40 PPM Mehlich III. Water samples are collected using ISCO samplers with only water from subsurface drainage collected.

Preliminary water quality results are presented below for the period January to September 2019. The surface placement plot yielded the highest concentration of DRP and loading in the collected tile water. All treatments that placed P2O5 in contact with the soil resulted in lower DRP concentrations and loading.

Figure 1. DRP Concentration and Load from phosphorus placement measured through subsurface drainage. Click Image to Enlarge

Corn and soybean yield average 144.4 and 47.7 bushels per acre respectively with no significant response to fertilizer placement. Yield response data is shown in Table 1 below.

Table 1. Corn and Soybean yield from phosphorus placement in 2019.

Placement Soybean (bu/A) Corn (bu/A)
Surf 45.8 132.0
2″by2″ 49.7 152.7
Deep 48.2 133.7
Incorp 47.0 159.2
LSD (0.1) 4.0 49
CV 4.2 17

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