Oakes Irrigation Research
Site
Carrington Research Extension Center * North Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Voice: (701) 742-2189, FAX: (701)
742-2700, email: rgreenla@ndsuext.nodak.edu
ALFALFA MULCH ON TOMATO STUDY, 2001
Richard Greenland
Table 60. Disease ratings and yield components
Table 61. Soil NO3-N values (soil samples collected Nov. 8 & 9)
Tomatoes grow well in southern North Dakota. Yield and quality may be reduced in cool years. In most years, yield and quality compare very favorably with other areas in the United States. Straw mulch placed around tomatoes can reduce weed pressure, decrease evaporation from the soil surface, provide organic matter, and keep the soil from splashing onto the tomato plants during rainfall and irrigation, which may help reduce disease. But straw can also immobilize N in the soil, preventing the tomato plants from getting the N they need. This can increase the incidence of early blight and reduce tomato yield. Nitrogen can be applied to overcome the effect of N immobilization by the straw. Alfalfa mulch, which contains about 2.5% N, could also be used. The N from the alfalfa becomes available as the alfalfa mulch decomposes. This can provide, if the decomposition rate of the alfalfa is timely, a continuous supply of N to the tomatoes, whereas applying chemical N tends to give a spike of N, especially in sandy soils with little buffering capacity. This study was designed to test the effects of using alfalfa as a mulch and fertilizer on tomatoes.
Soil: |
Embden loam; pH=7.4; 2.5% organic matter; soil-P and soil-K were very high; soil-S was very low. |
Previous crop: |
2000 - carrot; 1999 - field corn; 1998 - edible bean. |
Seedbed preparation: |
Disked on May 16. Multiweeded (field cultivated) five times; once on May 16 to incorporate fertilizer, twice deep and twice shallow on May 24 to incorporate herbicides and to smooth seedbed. |
Planting: |
Tomatoes were seeded in the greenhouse on April 8. Plants were transplanted to the field on May 24. Rows were spaced 4 feet apart. In-row spacing was 1 ft. As it was planted, each plant received one pint of fertilizer solution (1 gal 10-34-0 in 100 gal of water). Tomatoes were not staked. |
Plots: |
Plots were 10 ft long by 8 ft (2 rows) wide. |
Fertilizer: |
On April 19, broadcast 10 lbs N/acre and 50 lbs P2O5/acre as 10-50-0 and 18 lbs N/acre and 20 lbs S/acre as 21-0-0-24. Sprayed 50 lbs N/acre as 28-0-0 on May 16. See Table 59 for remaining treatments. |
Irrigation: |
Overhead sprinkler irrigation as needed. |
Pest control: |
Weeds were controlled by Tillam and Treflan (3 qt/acre and 1 pt/acre on May 24: Tillam was applied and incorporated 4 inches deep then Treflan was applied and incorporated 2 inches deep), Shadeout (1 oz/acre on July 3), and by hand weeding. Sprayed Asana (8 oz/acre on Aug 15) for insect control. Fungicide treatments were applied to half of each rep as: Bravo (3 pt/acre on July 10 and July 17), Ridomil MZ72 (2.5 lb/acre on July 24 and Aug 15), and Quadris (6 oz/acre on Aug 6). |
Harvest: |
Harvested a 5-foot section from 2 rows on Aug 22 to Aug 24. |
Table 59. Mulch treatments for the 2001 tomato/mulch study at the Oakes Irrigation Research Site.
Mulch
1. Standard, no mulch, 50 lbs N/acre (as urea) at bloom (June 21) and 50 lbs N/acre (as urea) July 30.
2. Straw mulch after transplanting, 100 lbs N/acre (as urea) at bloom (June 21) and 50 lbs N/acre (as urea) July 30.
3. Alfalfa mulch 15 lbs/plot (= about 4 ton/acre = about 200 lbs N assuming alfalfa was 2.5% N) + Straw mulch after transplanting.
Fungicide
No fungicide vs. fungicide applied weekly starting July 10.
Table 60. Disease ratings and yield components for the 2001 tomato/mulch study at the Oakes Irrigation Research Site.
Treatment |
Disease rating1 |
Red tomato yield |
Green tomato yield |
US#1 yield |
Total yield |
Total No. of fruit |
Fruit size |
||
US#1 |
total |
US#1 |
total |
||||||
|
1 to 10 |
------------------------------------ tons/acre ------------------------------------- |
1000s/acre |
oz/fruit |
|||||
Mulch2 |
|||||||||
None |
7.1 |
16.3 |
26.6 a3 |
14.7 |
15.8 |
30.4 |
44.8 |
234 |
6.2 |
Straw + N |
6.9 |
16.1 |
29.5 a |
10.9 |
14.8 |
26.9 |
44.2 |
243 |
5.8 |
Straw + alfalfa |
8.0 |
12.9 |
21.2 b |
15.5 |
19.3 |
27.9 |
42.0 |
230 |
5.9 |
Probability |
0.16 |
0.07 |
0.02 |
0.24 |
0.58 |
0.22 |
0.71 |
0.84 |
0.59 |
Fungicide |
|||||||||
No |
6.8 |
13.6 |
25.6 |
13.2 |
19.0 |
27.3 |
44.7 |
261 |
5.5 |
Yes |
7.8 |
16.5 |
25.9 |
14.2 |
14.3 |
29.5 |
42.7 |
211 |
6.5 |
Probability4 |
0.02 |
0.13 |
0.90 |
0.33 |
0.24 |
0.22 |
0.61 |
0.09 |
0.02 |
C.V. (%) |
8 |
18 |
21 |
29 |
23 |
10 |
2 |
12 |
10 |
1The higher the rating the lower the disease.
2See Table 59 for description of mulch treatments.
3Values in this column followed by the same letter are not significantly different at the 0.05 level.
4If probability is less than 0.05 then there is a significant difference between fungicide vs. no fungicide for that column.
Table 61. Soil NO3-N values for the tomato mulch trial (soil samples collected Nov. 8 & 9).
Treatment1 |
Soil depth sampled |
|||
0 to 3" |
3 to 6" |
6 to 24" |
0 to 24" |
|
|
--------------------------------- lbs/acre ------------------------------------ |
|||
Mulch |
||||
None |
6.9 |
5.1 |
11.6 |
23.6 |
Straw + N |
7.4 |
4.8 |
9.4 |
21.5 |
Straw + alfalfa |
9.9 |
5.3 |
9.8 |
24.9 |
Probability |
0.002 |
0.51 |
0.49 |
0.41 |
Fungicide |
||||
No |
7.8 |
4.8 |
10.5 |
23.1 |
Yes |
8.3 |
5.3 |
10.0 |
23.6 |
Probability2 |
0.56 |
0.21 |
0.50 |
0.77 |
C.V. (%) |
20 |
24 |
31 |
23 |
1See Table 59 for a description of treatments.
2If probability is less than 0.05 then there is a significant difference between fungicide vs. no fungicide for that column.
To test the effect of the mulch treatments on tomato disease (mostly early blight) we left half of the plots without any fungicide treatment. The plots receiving fungicides had slightly less disease and larger fruit than those not receiving fungicide. The tomatoes with the straw plus alfalfa mulch tended to have less disease than the other two treatments, but statistically the difference was not significant. The straw plus alfalfa decreased red tomato yield but not total (red plus green) yield. This indicates that the straw plus alfalfa delayed maturity of the tomatoes. The maturity could have been delayed because of stress or because of too much N. The two treatments with straw mulch tended to have more tomatoes eaten by rodents or insects than did the check treatment. Slightly more NO3-N was left in the upper three inches of the soil profile following the alfalfa treatment, but there were no differences between the treatments in the amount of residual N left in the top two feet of the soil profile.
Go to Oakes Irrigation Research Site Cover Crop Study page
Go to Oakes Irrigation Research Site 2001 annual report