Seed-placed nitrogen performance depends on the type of pulse crop

Pulse crops have different tolerances and performance from seed-row placed nitrogen. | File photo

Getting the rate right with seed-row placed fertilizer in pulses can mean the difference between giving the crop a good start, hindering it, or simply wasting money applying products the plants can’t use.

Jeff Schoenau, a soil fertility specialist and professional agronomist at the University of Saskatchewan, looked at seed-row placed fertilizer in six different pulse crops. The aim was to find out how well the crops tolerated fertilizer blends containing nitrogen.

Schoenau ran trials with starter products containing nitrogen, phosphorus and sulphur (N,P,S). Application rates were 10, 20, and 30 kilograms of N per hectare.

He found that lentils, peas and chickpeas could handle no more than 10 kilograms per hectare without risking injury. Soybeans and black beans could tolerate up to twice this amount. Fababeans could handle the maximum rate with no effect on emergence and were the least sensitive to seed-row placed fertilizer.

To assess performance, Schoenau measured biomass of the crops over 30 days. Here, soybeans and black beans showed the best response to fertilizer, something attributed to these crops being slower off the mark in establish nitrogen-fixing rhizobacteria and associated root nodules.

Nutrient uptake and plant growth for pea, fababean, lentils and chickpeas were more modest in response to the starter fertilizer blends. There was no observed benefit at applications above 10 kilograms per hectare.

Under field conditions, Schoenau found that soybeans and lentils seeded with a nitrogen phosphorus (28-26-0) blend at 10 kg per hectare appeared to deliver the best performance. That is, there were minimal effects on emergence, stand count and nitrogen fixation, while nutrient uptake and yield were maximized. Rates higher than this reduced emergence and interfered with rhizobacteria and nodulation.

Schoenau’s research was funded through Saskatchewan Pulse Growers and the Saskatchewan Ministry of Agriculture.

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