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Fluid Journal : Fluid Journal 1999-2001
Spring 2000 Summary: NBPT reduced seedling toxicity and canola stand reduction when increasing rates of UAN were applied to clay loam soils. Without NBPT, significant stand reduction occurred. On fine sandy loam soils, no significant stand reduction occurred with increasing rates of UAN. Apparent cause may have been high rainfall after seeding that reduced N toxicity. Biomass yield at flowering increased linearly with N fertilizer application on clay loam soils. On fine sandy loam soils, N management did not influence biomass. Seed yield on both soils increased with increasing N rates. _________________________________ Reduced tillage systems are being adopted by more and more pro- ducers in Canada who list canola as one of their major crops. Canola is grown on more than 13 million acres and represents nearly a $3 billion market. Reducing the number and intensity of tillage operations allows producers to improve water-use efficiency, lower costs of crop production, decrease time required for field operations, and reduce the risk of soil erosion and degradation. More and more producers are also moving toward seeders that are equipped to side-band fertilizer near the seed. A problem for these producers, however, is that canola is more sensitive to seed damage than cereal grains when side- banding N near the seed. It is a crop requiring high nutrient levels, but characteristically also one deficient in nitrogen (N), which limits canola yields. Along with the trend toward side- banding fertilizer near the seed is the increasing use of wider row spacing. The practice reduces draft requirement, price of equipment, soil disturbance, and problems with trash clearance. In the past, many held to the opinion that separation of the seed and fertilizer by one to two inches was sufficient to ensure crop safety under most soil conditions. However, when row spacing increased to 12 inches, concentration of fertilizer near the seed increased when compared to traditional 6- to 9-inch row spacings. This could reduce the amount of fertilizer that can safely be applied as a side-band. Recent studies have shown reduced performance of canola with 12-inch spacings and side-banded, although fertilizer rates used were approximately two-thirds of recommended levels. The reduced performance might have been due to seedling toxicity from fertilizer, since canola is very prone to seedling damage. A more recent study has examined more closely the impact of side-banded fertilizer on canola growth at 9- and 12-inch row spacings. Damage from high fertilizer rates was apparent at the wide row spacing at some locations. In most crops, urea is considered to be more damaging to seedling emergence than nitrate sources of N. This is because urea converts to ammo- nia that is directly toxic to germinating seedling. It also creates a desiccating "salt effect." In contrast, nitrate only causes damage through salt effect. Therefore, toxicity is believed to increase in the order of ammonium nitrate<UAN<urea. However, other studies have shown urea was no more harmful to canola than was ammonium nitrate, under specified conditions, sug- gesting that canola might be more sensi- tive to salt effects than ammonia toxicity. Other recent studies have shown that urea toxicity can be reduced in barley and wheat by applying NBPT (Agrotain). This may or may not be effective in canola, depending on the importance of ammonia toxicity and the effect of slow ammonia release from urea on salt effect near the seed. To search out the effects of NBPT, we designed a study in 1999 to evaluate the effects of increasing side- banded UAN rates on canola seedling, with the following objectives: • Determine the effectiveness of Drs. C. A. Grant, D. A. Derksen, D. McLaren NBPT Reduces Seedling Damage In UAN Trials Canadian no-till canola studies find NBPT helps maintain stand density when increasing rates of side-banded UAN in certain soils.
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