Malheur Experiment Station Information for Sustainable Agriculture

Sugar beet nitrogen fertilizer guidelines are based on either fall or spring nitrate-N levels to 3-foot depth in the soil and total plant needs estimated at 8 pounds N per ton of beets. These assumptions provide estimates for N fertilization which have been useful for many years. To make beet production and processing as efficient as possible, it is important to use only the N fertilizer needed to grow the crop. In the cases where soil organic matter mineralization is large compared with residual soil nitrate or fertilization, the current guidelines could over-estimate crop fertilizer needs.

When sugar beets receive N in excess of their needs, total beet yield and leaf growth are high, but both beet sugar content and total sugar yields can be depressed. Extra nitrate and ammonium in the beet pulp reduce sugar factory efficiency.

The objectives of this study were to examine the amount and importance of N mineralized from soil organic matter in commercial sugar beet fields and to make observations of sugar beet plant N uptake in N fertilizer trials conducted by beet fieldmen in commercial fields to improve our understanding of beet responses to N fertilizer.

Sugar beet fieldmen have conducting N fertilizer rate trials in growers fields during the last few years. These trials have the basic structure of large plots with several N rates and one to three replicates. In general the recommended N fertilizer rate is based on the soil nitrate present in the soil profile to a depth of 3 feet in each field and a yield goal for that field. Other large field plots are treated with twice the recommended N rate, half the recommended N rate, and no fertilizer as the check. In a few fields with high residual nitrate, the fieldman and grower opted to leave all plots unfertilized. Twelve growers' fields were studied through harvest in 1994 and an additional eight fields in 1995 between Brogan, Oregon, and Burley, Idaho (Table 1). Several other fields were set up each year, but their experimental value was lost in cultivation or harvesting errors.

The growers take care of all of the cultural practices and the fertilizers are applied in cooperation with fertilizer industry representatives. Sugar beet fieldmen kept track of crop progress and coordinated the harvest, collecting yield and quality data based on the entire field plots. Beets were evaluated for total yield, tare, sucrose content, conductivity, and beet pulp nitrate by the Amalgamated Sugar Co.

Additional work was done by the Malheur Experiment Station. The percent sugar extraction and recoverable sugar were calculated based on empirical formulas. Soil samples were collected in the spring for estimates of N mineralization via three methods: anaerobic incubation, aerobic incubation, and the buried-bag method. Twelve to fourteen representative beets with their leaves and crowns were harvested from each plot just prior to harvest and taken to the Malheur Experiment Station. Leaves and crowns were dried, weighed, ground, and analyzed for total N content. The beets were weighed fresh after the leaves and crown were removed, ground, and a subsample of the beet pulp was weighed wet and oven-dried to determine dry matter content, then analyzed for total N content. Beet N uptake per acre in the leaves, crowns, and beets was calculated based on the clean beet yield of each plot, the beet dry weight to fresh weight ratio, the proportion of dry crown and leaf tissue to dry beet in the tissue samples, and the tissue sample N contents.

Total available soil N supply was calculated based on the sum of spring available nitrate and ammonium, any applied fertilizer N, and N mineralization (estimated by anaerobic incubation or seasonal N balance). Nitrogen use efficiency was calculated for each plot by dividing the total plant N uptake by the total available N supply for each plot and multiplying by 100.

Spring soil nitrate N ranged from 61 to 284 lb N/acre, depending on the field (Table 2). Optimistic yield goals ranging from 25 to 40 tons of beets per acre implied N fertilizer needs of 0 to 216 lb N/acre. The lowest applied N rates were 0 lb N/acre at thirteen of the twenty sites.

The 1994 season was favorable for high yields (Table 3), and all cooperating growers kept weeds and diseases under control. The 1995 season was far less favorable, with lower temperatures and cloud cover during the growing season. Repeated rainfall events in 1995 made efficient N use difficult and reduced residual nitrate and ammonium in the fields at harvest. Repeated hail in the Treasure Valley was damaging at certain locations.

The highest-yielding N fertilizer rates ranged from 0 to 205 lb N/acre depending on the field studied. Sugar beet response to N fertilizer varied substantially. Reasonable yields were obtained in certain fields with low rates of N fertilizer (Tables 2 and 3). Beet pulp nitrate at 0 applied N suggested that there was extra N supplies in five fields without any fertilizer nitrogen (Table 3). Beet petiole nitrate was consistent with high yields at low N fertilizer inputs in these fields (data not shown).

The optimal N rate was determined independently for each field based on the highest yield of recoverable sugar. Beet plants at the optimal-applied N levels contained 126 to 426 lb N/acre at harvest depending on the field (Table 4). Anaerobic incubation estimates of N mineralization ranged from 88 to 251 lb N/acre depending on the field (Table 5). Mineralized N appears to be a large N source averaging 163 lb N/ac over the 20 fields (Table 4). Fields with high spring residual nitrate are not necessarily going to have high rates of N mineralization; fields with low spring residual nitrate are not necessarily going to have to low rates of N mineralization , r² =0.029.

In 1994, the anaerobic incubation estimates of N mineralized ranged in the same order of magnitude as field method of N balance method. The N balance method was based on measuring residual soil nitrate and ammonium at harvest and plant N content at harvest, then subtracting all known available N sources. The N balance was not comparable in 1995, as would be expected after a season with untimely rainfall events.

At the most productive N level tested at each site, sugar beets were able to recover between 40.4 and 88.8 percent of the estimated total N supply (based on the sum of soil nitrate and ammonium to the 3-foot depth, fertilizer N, and N mineralization in Table 4). Efficiencies less than 75 percent appear to be related to very high N supply at 0 N applied, irrigations and rainfall in excess of evapotranspiration, or sugar beet cyst nematode.

These trials depended of the work of many growers and fertilizer fieldmen, without which the effort would have been impossible.

Table 1. Characteristics of 20 sugar beet fields used for soil N mineralization studies in 1994 and 1995. Malheur Experiment Station, Oregon State University, Ontario, Oregon. 

Field	Location	Soil texture	pH	Organic matter	Soil depth	Variety	Planting  date	Irrigation system	Comments	Previous crop
1994				%
1	Burley	sandy loam	8.4	1.25	> 6'	MH 9455	April 11	side roll	cyst nematode	Beets
2	Minidoka	silt loam	8.0	1.5	2.5'	PM-9	March 19	side roll	rock at 2-3'	Wheat
3	Minidoka	silt loam	8.0	2.35	2.5'	WS91	March 20	side roll	rock at 2-3'	Wheat
4	Jerome	loam	7.55	1.05	2.5'	WS91	April 25	side roll	rock at 2-3'	Potatoes
5	Nyssa	silt loam	7.65	1.4	>6'	PM-9	last week March	furrow		Onions
6	Ontario-Vale	fine sandy loam	7.5	1.6	>6'	PM-9	March 7	furrow		Onions
7	Ontario-Vale	silt loam	7.75	2.2	>6'	PM-9	March 12	furrow		Onions
8	Ontario-Nyssa	fine sandy loam	7.4	1.75	>6'	PM-9	2nd week March	furrow		Onions
9	Nyssa	silt loam	7.9	2.1	>6'	PM-9	March 26	furrow	B deficient	Potatoes
10	Vale	silt loam	7.6	2.05	>6'	PM-9	March 18	furrow		Onions
11	Brogan	silt loam	7.6	1.6	>6'	RSW-81	March 14	furrow		Onions
12	Ontario	silt loam	7.6	1.5	>6'	PM-9	April 5	furrow		Beans
1995
1	Buhl	silt loam	8.1	1.2	>6'	PM-9	May 10	furrow		beans
2	Burley	silt loam	8.1	1.49	2.5'	Beta 8422	April 10	side roll		wheat
3	Rupert	sandy loam	7.8	1.28	>6'	WS62	April 20	furrow		beans
4	Minidoka	silt loam	8.2	1.65	2.5'	PM-9	April 4	side roll		potatoes
5	Nyssa	silt loam	7.6	1.45	>6'	PM-9	March 30	furrow	rhizoctonia	onions
6	Vale	silt loam	7.8	3.29	>6'	PM-9		furrow		potatoes
7	Ontario	silt loam	7.7	1.43	>6'	PM-9	March 29	sideroll		potatoes
8	Nyssa	silt loam	7.4	1.47	>6'	PM-9	March 27	furrow	rhizoctonia, flooding	beans

Table 2. Optimistic yield goals, soil nitrate, recommended N fertilizer rates, grower's preferred N fertilizer rates, and best fertilizer N rates for 1994 and 1995. Malheur Experiment Station, Oregon State University, Ontario, Oregon. 

Field	Location	Optimistic yield goal	Soil nitrate 0-3'	Total N needed for optimistic yield goal	Recommended N fertilizer for optimistic yield goal	Growers' preferred N rate	Lowest N rate used in l994 trial	Highest yielding N rate for 1994 trial
1994		t/ac	- - - - - - - - - - - - - - - - - - - - - - - lb N/ac - - - - - - - - - - - - - - - - - - - - - - -
1	Burley	28	164	224	60	80	0	40
2	Minidoka	35	171	280	109	110	0	110
3	Minidoka	35	85	280	195	205	80	205
4	Jerome	35	155	280	125	50	0	25
5	Nyssa	40	207	320	113	-	0	0
6	Ontario-Vale	40	284	320	36	75	0	0
7	Ontario-Vale	40	238	320	82	0	0	0
8	Ontario-Nyssa	40	148	320	172	-	60	60
9	Nyssa	40	165	320	154	-	60*	80
10	Vale	40	356	320	-36	150	0	0
11	Brogan	35	165	280	115	100	0	0
12	Ontario	40	104	320	216	-	0	0
1995
1	Buhl	25	199	200	1	100	0	0
2	Burley	25	61	200	139	160	80	160
3	Rupert	35	95	280	185	120	19	171
4	Minidoka	25	105	200	95	163	0	85
5	Nyssa	30	115	240	125	100	35	35
6	Vale	40	122	320	198	150	0	150
7	Ontario	34	108	272	164	170	80	80
8	Nyssa	32	138	256	118	100	0	40
*Boron deficient part of field.

Table 3. Beet yield and quality at the best N rate for each of 20 growers' fields. Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1994 and 1995.

Summary of characteristics					Highest yielding plant performance
Field	Location	Optimistic yield goal	Soil nitrate 0-3'	Most productive N rate for 1994 trial	Clean beet yield	Sucrose	Conductivity	Extraction	Recoverable sugar	Pulp nitrate
1994		t/ac	lb N/ac	lb N/ac	t/ac	%		%	lb/ac	ppm
1	Burley	28	164	40	24. 0	16.9	0.73	86.4	6,998	187
2	Minidoka	35	171	110	35.5	18.1	0.73	86.5	10,799	148
3	Minidoka	35	85	205	39.2	17.4	0.9	84.2	11,479	na
4	Jerome	35	155	25	32.7	16.8	1. 00	82.8	9,064	411
5	Nyssa	40	207	0	31.3	15. 0	0.84	84.7	7,950	552
6	Ontario-Vale	40	284	0	40.9	15.8	0.87	84.4	10,925	483
7	Ontario-Vale	40	238	0	34.8	13.7	1.09	81. 0	7,708	701
8	Ontario-Nyssa	40	148	60	39. 0	16.7	0.68	87.1	11,342	294
9	Nyssa	40	165	80	33.4	16.2	0.72	86.4	9,372	283
10	Vale	40	356	0	38.3	14.8	0.98	82.7	9,406	581
11	Brogan	35	165	0	29.4	14.9	0.95	83.1	7,280	629
12	Ontario	40	104	0	45.6	16.2	0.75	86.1	12,732	175
1995
1	Buhl	25	199	0	21.3	16.9	0.60	88.1	6,352	145
2	Burley	25	61	100	22.9	19.2	0.88	84.6	7,452	178
3	Rupert	35	95	171	31.9	16.6	0.77	85.8	9,110	313
4	Minidoka	25	105	85	21.4	16.6	0.62	87.8	6,787	152
5	Nyssa	30	115	35	25.2	16.3	0.72	86.4	7,078	243
6	Vale	40	122	150	31.4	14.9	1.06	81.6	7,630	691
7	Ontario	34	108	80	28.0	17.6	0.64	87.7	8,649	161
8	Nyssa	32	138	40	31.8	16.9	0.71	86.7	9,283	194

Table 4. Comparison of soil nitrogen supply, beet plant nitrogen content, and N use efficiency at harvest for beets grown at the highest-yielding N level in 20 fields. Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1994 and 1995.

		Best plant performance		N supply					Plant N content
Field	Location	Beet yield	Recoverable sugar	Most productive N rate for 1994 trial	Spring soil nitrate -N 0-3'	Spring soil ammonium -N 0-3'	Estimate of N-mineralization (anaerobic)	Total available N supply	Leaves	Crown	Beets	Total	Total plant N content at harvest per ton of beets	N use efficiency2
1994		t/ac	lb/ac		lb N/ac	lb N/ac	lb N/ac		lb N/ac				lb N/ton	%
1	Burley	24. 0	6,998	40	164	23	112	339	70	20	94	184	7.65	54.2
2	Minidoka	35.5	10,799	110	171	17	172	469	63	18	148	229	6.65	48.9
3	Minidoka	39.2	11,479	205	85	14	167	470	98	23	187	308	7.82	65.4
4	Jerome	32.7	9,064	25	155	16	135	331	103	15	145	263	8.07	79.5
5	Nyssa	31.3	7,950	0	207	64	88	359	127	18	150	295	9.42	82.3
6	Ontario-Vale	40.9	10,925	0	284	30	149	459	122	19	225	366	8.93	79.9
7	Ontario-Vale	34.8	7,708	0	238	32	251	520	162	17	197	376	10.87	72.4
8	Ontario-Nyssa	39. 0	11,342	60	148	48	115	371	111	23	180	314	8.06	84.6
9	Nyssa	33.4	9,372	80	165	31	97	373	87	27	129	243	7.26	65.1
10	Vale	38.3	9,406	0	356	39	236	631	165	35	226	426	11.06	67.5
11	Brogan	29.4	7,280	0	165	48	224 1	437 1	100	37	164	301	10.08	68.9 1
12	Ontario	45.6	12,732	0	104	49	292 1	445 1	123	46	226	395	8.65	88.8 1
1995
1	Buhl	21.3	6,352	0	199	--	95	294	88	8	78	174	8.20	59.2
2	Burley	22.9	7,452	100	61	17	158	336	79	5	65	149	6.50	44.4
3	Rupert	31.9	9,110	171	95	--	195	461	92	9	116	217	6.79	47.1
4	Minidoka	21.4	6,787	85	105	--	130	320	52	6	77	135	5.80	42.2
5	Nyssa	25.2	7,078	35	115	34	121	305	52	4	70	126	5.00	41.3
6	Vale	31.4	7,630	150	122	27	210	509	130	13	112	255	8.10	50.1
7	Ontario	28.0	8,649	80	108	24	189	401	55	9	98	162	5.80	40.4
8	Nyssa	31.8	9,283	40	138	30	136	344	72	8	136	216	6.80	62.8
1N mineralization estimate by season-long N balance.
2Total plant N content as a percent of the total available N supply.

Table 5. Estimates of N mineralization made in 20 growers' sugar beet fields by four different methods. Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1994 and 1995. 

				N-mineralization estimate
Grower	Location	Soil texture	Organic matter	Anaerobic incubation	Aerobic incubation	Available nitrogen balance	Buried bags
1994			%	- - - - - - - - - - - - - - - - lb N/ac - - - - - - - - - - - - - - - - -
1	Burley	sandy loam	1.25	112	170	-	-
2	Minidoka	silt loam	1.5	172	155	-	-
3	Minidoka	silt loam	2.35	167	137	-	-
4	Jerome	loam	1.05	135	132	283	110
5	Nyssa	silt loam	1.4	88	120	238	-
6	Ontario-Vale	fine sandy loam	1.6	149	182	238	-
7	Ontario-Vale	silt loam	2.2	251	298	304	-
8	Ontario-Nyssa	fine sandy loam	1.75	115	134	125	-
9	Nyssa	silt loam	2.1	97	110	61	-
10	Vale	silt loam	2.05	236	291	251	-
11	Brogan	silt loam	1.6	149	-	224	-
12	Ontario	silt loam	1.5	159	123	293	255
1995
1	Buhl	silt loam	1.2	95		-
2	Burley	silt loam	1.49	158		-11
3	Rupert	sandy loam	1.28	195		12
4	Minidoka	silt loam	1.65	130		3
5	Nyssa	silt loam	1.45	121		16
6	Vale	silt loam	3.29	210		-
7	Ontario	silt loam	1.43	189		48
8	Nyssa	silt loam	1.47	136		38

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Malheur Agricultural Experiment Station

Last updated  Tuesday July 30, 2002 .