2000 Agricultural Research Update

The study was conducted under sprinkle irrigation at the Eastern Agricultural Research Center in Sidney. The objective was to determine N recommendations for irrigated durum, and to compare durum and spring wheat responses to applied nitrogen. Residual soil N to 4 feet was 45 lb/ac, residual soil P to 6 inches was 33 ppm, and residual soil K to 6 inches was 510 ppm. Nitrogen was expected to be released from tops of the sugarbeet crop grown in the year prior to the study (50 lb/ac) and from organic matter in the soil (75 lb/ac). Nitrogen was applied as granular ammonium nitrate (34-0-0) to the plots at six rates on 20 April 2000, and immediately incorporated. ‘Ben’ and ‘Monroe’ durum and ‘McNeal’ spring wheat were planted on 20 April in 12-row plots. Nitrogen was topdressed on four rows of each plot in the form of granular ammonium nitrate (34-0-0) at a rate of 40 lb/ac on 30 May and the site was immediately sprinkle irrigated. Thio-sul (12-0-0-26S) mixed with liquid 28-0-0 and was applied in liquid form on 6 June 2000 at a rate of 40 lb N/ac and 26 lb S/ac. The liquid was diluted, but not enough, because leaf burn was noted on the Thio-sul plots within several hours of fertilizer application. Plots were sprinkle irrigated on 25 April, 3 May, 30 May, 12 June, 27 June, 20 July. Plots were harvested with a plot combine on 31 July.

Yields were not as great as in the past, partly due to bird damage of the durum. Topdressed N increased Monroe and Ben durum and McNeal spring wheat yields at the low preplant rates. Top dressed N boosted protein of durum at the lower rates of preplant N , and boosted spring wheat protein at the upper rates of preplant N. Increased preplant N reduced test weight in all varieties.

N rate, lb/acre		‘Ben’ durum			‘Monroe’ durum			‘McNeal’ spring wheat
Preplant	Topdress	Yield Bu/ac	Test Weight	Grain protein	Yield Bu/ac	Test Weight	Grain protein	Yield Bu/ac	Test Weight	Grain protein
0	0	56.4	61.6	14.2	57.5	62.4	13.1	71.9	60.0	12.4
	40	67.4	61.2	14.7	68.0	61.8	13.8	81.2	59.4	12.4
	TS*	65.8	61.4	14.4	59.8	62.2	13.1	73.0	60.2	12.6
30	0	63.6	61.2	13.7	66.8	62.2	13.3	77.0	59.2	12.4
	40	67.9	60.7	14.5	77.0	62.0	13.8	81.8	59.4	12.7
	TS*	66.6	60.4	14.3	71.6	62.1	13.6	76.3	59.2	12.5
60	0	64.0	60.6	14.6	73.2	61.4	14.2	79.2	59.9	12.5
	40	65.6	59.6	15.2	78.6	61.4	14.3	82.7	59.1	13.0
	TS*	65.4	60.2	15.1	73.1	61.4	14.3	76.4	59.9	13.1
90	0	71.4	60.6	14.6	70.7	61.1	14.0	79.4	59.8	12.8
	40	75.0	59.5	14.8	77.4	61.4	14.6	83.5	58.2	13.3
	TS*	71.0	59.8	14.9	68.3	60.9	14.1	78.5	59.5	13.8
120	0	69.5	59.5	15.0	74.4	61.4	14.1	82.4	59.6	12.7
	40	72.7	59.9	14.9	76.2	61.4	14.7	87.3	58.4	13.4
	TS*	70.2	60.0	14.4	75.9	61.2	14.0	79.8	59.2	13.0
150	0	70.9	60.0	14.7	82.9	60.9	14.1	82.2	57.6	13.0
	40	74.0	59.9	14.5	85.6	61.1	14.6	84.2	58.2	13.4
	TS*	64.2	59.1	15.1	79.5	60.9	14.3	80.6	58.9	13.8
	LSD _0.05	8.5	1.1	0.6	7.2	0.7	0.5	6.0	ns	0.8

Acknowledgements:
Funding for this project was provided by grants from the Montana Fertilizer Advisory Committee and the Jupiter Sulphate Company

N rate, lb/acre

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Last modified: August 04, 2003