Page 212 - Nutrient Management Planning Guide

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Chapter 5.1

Getting the Best Results from Banding P Fertilizers

Here are some additional tips on successfully banding P fertilizers: Keep the spacing between bands narrow (less •

than 30 cm or 12 in), so P uptake is not delayed during early growth due to distance between bands and seedlings. On very low P soils stripping can occur. This is caused by poorer growth of plants midway between phosphate bands when the bands are too widely spaced.

Band P fertilizer deep enough to avoid •

disrupting the bands during subsequent tillage and seeding operations.

Avoid banding P and N fertilizers together if N •

is being applied at rates higher than 70 to 80 kg/ha (63 to 72 lb/ac). The high rate of N will reduce the efficiency of P fertilizers because plant roots cannot penetrate the concentrated N band and are less effective at taking up P.

Foliar

In foliar fertilization, nutrients are sprayed onto leaves, stems, and soil surfaces with conventional spraying equipment. Foliar applications are not effective for most nutrients (N, P, K, and S) because leaves cannot absorb enough nutrients for plant growth. Without rainfall or irrigation after application, foliar fertilizers are ineffective, and will only damage plants through fertilizer burn. Some forms of micronutrients are effective when foliar applied (Table 5.1.2).

Fertigation

Fertigation is the application of nutrients through irrigation water. It allows nutrients to be supplied throughout the growing season to meet crop demand. To be effective, nutrients should be delivered with a minimum of 1.5 to 2.0 cm of water to move the nutrients into the soil. Unlike foliar applications, fertilizer burn is not a problem with fertigation because of the amount of water that is applied.

If inadequate water is applied the fertilizer nutrients can be lost through volatilization or stranded at the soil surface out of reach of plant roots. Depending on the quality (hardness) of the water, precipitates (such as calcium phosphates) can form from the combination of fertilizer and cations in the irrigation water.