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Comparison of several organic amendments with a chemical fertilizer for vegetable production
Scientia Horticulturae, 47 ( 1991 ) 177-191
177
Elsevier Science Publishers B.V., Amsterdam
Comparison of several organic amendments with a chemical fertilizer for vegetable production C.R. Blatt Agriculture Canada, Research Station, Kentville, N.S. B4N l J5, Canada (Accepted 22 January 1991 )
ABSTRACT Blatt, C.R., 1991. Comparison of several organic amendments with a chemical fertilizer for vegetable production. Scientia Hortic., 47:177-19 I. Field research was conducted for seven seasons (1983-89) on three soil types comparing several organic amendments (dry and liquid fish silage, fish bone meal, blood meal, meat meal, seaweed meal, seaweed extract ) with a chemical fertilizer ( 17-17-17 ) applied to seeded beans, carrots, peas and sweet corn, and transplanted broccoli, Brussels sprouts, cabbage, cauliflower and lettuce. In most instances, amendments were compared singly with a chemical fertilizer with different rates of nitrogen (N) and methods of application studied each season. In the last season ( 1989 ), combinations of fish bone meal, blood meal, meat meal and a seaweed concentrate were compared with pelleted fish silage (ground fish and herring), fish bone meal and a chemical fertilizer. For the cropping seasons 1983-88, in the majority of comparisons, plants receiving the organic amendments produced crops of comparable yield and size to those from plants receiving the chemical fertilizer. In 1989, plants receiving the chemical fertilizer had significantly higher yields than plants receiving any of the organic treatments. Soil and leaf nutrient values were not consistently affected by the soil type, fertilizer material, rate of N or method of application. Keywords: blood meal; fish bone meal; fish silage; meat meal; organic amending; seaweed products; vegetables.
INTRODUCTION
Research with fish waste products has dealt primarily with the addition of liquid fish soluble nutrients (FSN) as a soil drench or a dilute foliar spray to various crops grown in greenhouse sand culture and field plots (Aung and Flick, 1980; Aung et al., 1981; Emino, 1981 ). Mineral analyses of the edible portion of several vegetable crops grown under greenhouse conditions showed that plants fertilized with FSN exhibited either no heavy metal accumulation or no excessive heavy metal accumulation compared with plants fertilized with standard Hoagland nutrient solution (Aung et al., 1983 ). Fish solubles have been used in chemical liquid fertilizer formulations for growing house,
178
C.R. BLATT
garden and glasshouse plants. Recently, Blatt and Sanford (1990) reported that fish bone meal and liquid fish silage were suitable alternatives to a chemical fertilizer for the production of field-grown red beets and that there were no significant differences in the flavour of the beetroots due to the source of plant nutrients. Glasshouse trials (C.R. Blatt, unpublished data, 1983 ) with transplanted vegetables indicated a possible benefit from a pre-plant application of dry fish silage. Although home garden and glasshouse crops could utilize a portion of the fish waste produced, there is a larger proportion that is unused by agriculture and could potentially be an alternate source of plant nutrients if the economics of manufacture and transportation were found to be competitive with chemical fertilizers. In the Atlantic region, one of the larger volume fish waste products is fish silage which, when properly treated, can be stored and subsequently used as a liquid or dry source of plant nutrients. Other products that could potentially be sources of plant nutrients include fish bone meal, seaweed meal, seaweed concentrate, blood meal and meat meal. The objective of the present study was to compare these organic amendments with a chemical fertilizer for the production of vegetable crops. MATERIALS AND METHODS - - Three soil types (Cann et al., 1965 ) were utilized during the course of these experiments (Table 1 ). Soil nutrient values are given as a range over all replicates and over all sites where a soil type was used for more than one season. In each experiment, soil samples (0-15 cm depth) were taken from each plot during the growing season and analysed for pH ( 1 : 1 soil: water);
Soils.
TABLE 1 Soil analyses of three soil types in which vegetables were grown when comparing several organic amendments with a chemical fertilizer Soil type
Crop season
pH
OM (%)
N~ ( k g h a -~)
Ca (kgha -~)
Mg (kgha - l )
K (kgha -~)
Berwick sandy loam
1983
5.5-5.6
5.0-7.5
45-50
1350-1440
490-510
160
Cornwallis loamy sand
1984, 1985, 1986
5.6-6.1
2.0-4.0
45-55
1300-1930
180-210
120-160
260-350
Somerset sandyloam
1987, 1988, 1989
6.0-6.5
4.0-6.0
35-70
2016-3810
535-670
170-350
560-780
Mineralizable N as NH4N.
P (kgha -~) 25- 50
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES
| 79
organic matter (OM) (K2Cr207; Atkinson et al., 1958 ); Bray #2 phosphorus (P) (Bray, 1948 ) using the molybdovanadate complex for colour development; and extractable calcium (Ca), magnesium (Mg) and potassium (K) (Mehlich, 1978 ) using atomic absorption spectrometry. Mineralizable nitrogen (N) (Waring and Bremner, 1964) was determined on a representative soil sample (0-15 cm depth ) from each soil type in an attempt to characterize the potential soil N status. Crops and crop management. - - Vegetables grown included broccoli ( Brassica oleracea L., Botrytis group), Brussels sprouts (Brassica oleracea, Gemmifera group), cabbage (Brassica oleracea L., Capitata group), cauliflower (Brassica oleracea L., Botrytis group ), lettuce (Lactuca sativa), peas (Pisum sativum ), yellow beans (Phaseolus vulgar&), carrots (Daucus carota var. sativus) and sweet corn (Zea mays L.). Several vegetables were grown on each of the soil types during each cropping season; however broccoli, cabbage and cauliflower were standard crops over all soil types. Crops grown each season were: 1983 - broccoli, cabbage, cauliflower; 1984 - broccoli, cauliflower, lettuce, peas, beans, carrots; 1985 and 1986 - broccoli, Brussels sprouts, cabbage, cauliflower; 1987 - broccoli, Brussels sprouts, cabbage, cauliflower, sweet corn; 1988 and 1989 - broccoli, cabbage, cauliflower. All crops were grown in single-row plots, 4 × 0.9 m, with 0.4 m in-row spacing between transplants and standard seeding rates used for seeded crops. For all transplant experiments, the first and last plants in each plot were guard or non-record plants. Yield data included total plant top weight (kg) per plot for beans, carrots and peas, and marketable yield (g) and size (cm) per plant for transplanted crops and sweet corn. Percentages of early yield are recorded for crops in which treatment affected maturity. Recommended pesticides were applied as needed and hand cultivation was used for incorporating dry material sidedressings and weed control. Irrigation was applied during the 198789 seasons. A representative leaf sample was taken from each plot and consisted of the most recently mature fully expanded leaves. Samples were dried at 70°C and ground in a Wiley mill with sub-samples subjected to a HNO3HCIO4-H2SO4 digestion for total P, K, Ca and Mg. Total N was determined on separate sub-samples using an automated semi-micro Kjeldahl procedure (Tecator, 1981 ). K, Ca and Mg were determined on an atomic absorption spectrophotometer, and P was analysed colorimetrically using the molybdovanadate complex. Fertilizer and amendments. - - All dry pre-plant treatments were applied by hand and mechanically incorporated 7-10 days prior to planting; sidedressings were applied by hand 4-6 weeks after planting. Liquid pre-plant treatments were applied with a large watering container and sidedressings were applied by a tractor-mounted liquid applicator. 17-17-17 is a standard vege-
180
C.R. BLATT
table fertilizer and is applied commercially pre-plant at rates of N up to 150 kg ha -~. The 0-17-17 formulation was fabricated from concentrated superphosphate (46% P205 ) and KC1 (60% K:O ), and applied to equivalent rates of P and K to the 17-17-17 as an N control. Fish silage is a product of the groundfish industry and was prepared by grinding groundfish (cod, etc. ) offal and then adding formic acid (2% by wet weight) that enhances digestion and contributes to extended storage by increasing silage acidity. In 1988, silage was prepared with phosphoric and formic acids (each at 2% by weight) and strained in order to provide a product that could be applied with an ordinary farm sprayer. The nutrient content of the dry and liquid (formic acid ) silages that were used is presented in Tables 2 and 3, respectively. In subsequent experiments with dry fish silage ( 1984, etc. ), the product supplied was a combination of groundfish species with a nutrient analysis similar to the cod + perch mixture (Table 2 ). Powdered fish silage was pelleted using a dry pelleting process and used as an amendment in the 1985-87 seasons. Fish bone meal was derived as a by-product of the fish meal process utilizing fresh fish with the fish bone being extracted from the meal and ground prior to treatment application (Table 4). Blood meal and meat meal are byproducts of a local poultry rendering plant and these were blended together TABLE 2
Nutrient analyses of dry fish silage (non-pelleted), crabmeal and a combination of cod silage and crabmeal applied to vegetables in 1983 Treatment Cod Cod+perch Crabmeal Cod + crabmeal (4:1)
N (%)
P (%)
K (%)
Ca (%)
Mg (%)
Fe
Mn
Cu
Zn
B
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
9.8 10.2 3.6
5.0 4.4 1.5
0.8 1.0 0.25
6.4 5.6 16.6
0.15 0.14 0.95
65 59 193
10 7 240
6 3 37
51 52 85
T
9.0
4.3
0.75
8.7
0.32
115
64
12
59
7.3 14.3
TABLE 3
Nutrient analysis (FW basis) of liquid fish silage applied to vegetables in 1986, 1987 and 1988 Nutrient
%
Nutrient
ppm
N P K Ca Mg Dry matter
1-3 0.4-2.6 0.4 1.0 0.1 20 - 6 0
Fe Mn Cu Zn
4 -8 0.5-3.0 0.5-1.0 1 -6
4.7
181
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES TABLE 4
Nutrient analysis of dry fish bone meal applied to vegetables in 1986-1989 Nutrient
%
Nutrient
ppm
N P K Ca Mg Na
6 -10 5 -9 0.1 11 -18 0.5 1.0
B Fe Mn Cu Zn
5-20 500-1500 25-45 20-50 100-200
TABLE5
Nutrient analyses of pelleted groundfish silage (GFS), herring silage (HS), a mixture of GFS + HS, seaweed meal (SWM) and mixtures of fish bone meal (FBM), blood meal (BM), meat meal ( MM ) and seaweed extract (SWE) applied to broccoli, cabbage and cauliflower in 1989 Treatment
N (%)
P (%)
K (%)
GFS ~ HS I GFS+HS (1:1) SWM FBM+BM+MM (2:1:1) FBM+BM (1:1) FBM+BM+SWE (5:4:1) FBM+MM+SWE (5:4:1)
1.8 2.3 2.0
0.4 0.4 0.4
0.4 0.5 0.5
0.7 8.2
0.1 4.6
9.4
Ca (%)
Mg (%)
Na (%)
Fe (ppm)
Mn (ppm)
Cu (ppm)
Zn (ppm)
B (ppm)
0.7 3.9 0.5 4.8 0.6 4.3
0.2 0.2 0.2
343 613 418
33 42 37
6.0 5.9 5.3
31 42 37
62 74 69
1.9 0.8
1.3 0.8 8.4 0.2
1.0
135 392
28 7.0
1.5 4.5
33 59
91 37
5.2
1.0
9.6 0.2
1.2
722
9.0
8.1
53
25
7.8
5.9
2.9
10.2 0.3
1.6
581
10.0
9.2
56
23
7.9
5.1
2.5
8.6 0.2
1.3
206
7.8
7.7
73
18
~Dry matter ranged from 49 to 62%.
with fish bone meal and a seaweed extract in various ratios, and applied preplant (Table 5). Seaweed meal (Table 5 ) was produced by drying and grinding rockweed (Ascophyllum nodosum) and an extraction procedure was used to prepare seaweed extract. Groundfish and herring silages (Table 5 ) applied in 1989 were prepared with formic acid and then subjected to a wet pelleting process (patent pending). All organic amendments used singly and in combination were analysed for their nutrient composition by the chemistry laboratory of the Soils and Crops Branch, Nova Scotia Department of Agriculture and Marketing. Nitrogen in all the dry products was determined on a Leco automated Dumas System and in liquid fish silage by a modified Kjeldahl method
182
C.R. BLATT
following wet digestion. All other nutrients were determined with an inductively coupled argon plasma unit. Each experiment was conducted with four replications and data were analysed as a randomized complete block design with field replication treated as a block. In 1983-86, rows of different crops were nested within plots. In 1987-89, crops were planted in different areas within the same field with each set out as a randomized complete block. Comparisons among treatments were made using orthogonal contrasts or polynomial regressions. All calculations were made using Genstat 5 procedures (Payne, 1987).
Statistical
analysis.
--
RESULTS
The 1983 field trial was conducted on a sandy loam soil (Table 1 ) with soil pH, K and P levels initially lower than the average values found in a productive vegetable soil. No significant yield differences were evident when cabbage and cauliflower yield and broccoli head size data from plants receiving the chemical fertilizer were compared with values from plants receiving any amendment (Table 6). When supplied at an equivalent rate of pre-plant N (150 kg ha -1), only cod silage and the cod+crabmeal combination supported marketable yields of broccoli that were similar to the yield from plants receiving the chemical fertilizer. The rate of pre-plant N had little effect on yield and size. The 1984-86 trials were conducted on a Cornwallis loamy sand soil characterized by rapid internal drainage and low soil K and OM. Yields and head TABLE6 Effect of dry fish silage (non-pelleted) and a chemical fertilizer ( 17-17-17 ) on marketable yield and size of broccoli, cabbage and cauliflower in 1983 ~ Treatment
17-17-17 Cod Cod Cod+perch Cod+perch C o d + crabmeal (4:1) SEM ( n = 4 , d f = 15) ~Berwick sandy loam. wt. = weight.
N ( k g h a -1 )
150 75 150 75 150 150
Broccoli head
Cabbage head
Cauliflower head
wt. (g)
diameter (cm)
wt. (g)
diameter (cm)
wt. (g)
diameter (cm)
637 398 501 434 426 555
14.7 12.0 13.8 12.4 12.0 13.9
1305 1149 1218 1068 1291 1207
14.8 14.3 14.8 14.1 14.9 14.3
717 617 637 830 662 842
16.7 15.5 15.4 17.9 15.5 17.4
56.3
0.94
103.9
0.50
119.6
0.97
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES
18 3
TABLE 7 Effect of dry fish silage (non-pelleted) and a chemical fertilizer (17-17-17) on marketable yields of beans, carrots, peas, broccoli, cauliflower and lettuce in 1984 ~ Treatment 2
17-17-17 Fish silage SEM (n=4, df=3)
Bean
3944 3200 390.9
Carrot (g per plot)
Peas
9489 7173
394 162
392.8
53.9
Broccoli head
Cauliflower head
Lettuce head
wt. (g)
diameter (cm)
wt. (g)
diameter (cm)
wt. (g)
diameter (cm)
398 439
16.0 16.5
402 275
10.2 8.9
429 508
10.5 10.9
28.6
0.87
72.8
0.92
16.9
0.24
~Cornwallis loamy sand. 2Total N applied to seeded crops = 100 kg h a - ~; total N applied to transplanted crops = 150 kg h a - ~. wt. = weight. TABLE 8 Effect of dry fish silage (pelleted) and a chemical fertilizer ( 17-17-17 ), applied by two methods, on marketable yields (g per plant) of broccoli, Brussels sprouts, cabbage and cauliflower in 19851 Broccoli
Brussels sprouts
Cabbage
Cauliflower
Application method 2 Single Split
516 543
482 451
1671 1652
794 701
Treatment 17-17-17 Fish silage
546 513
536 396
1677 1646
773 722
SEM ( n = 8 , d f = 9 )
28.8
33.2
74.2
36.3
~Cornwallis loamy sand. :Single= 150 kg ha-1 N broadcast pre-plant. Split = 100 kg ha-~ N broadcast pre-plant plus 50 kg h a - ~N 4-6 weeks after planting.
size of the three transplanted vegetables were not significantly affected by fertilizer source when each vegetable was supplied with N at 150 kg h a broadcast pre-plant and incorporated (Table 7). Fish silage reduced germination in the carrot and pea plots, and led to a significant yield difference between fertilizer sources (Table 7 ). Marketable yields of broccoli, Brussels sprouts, cabbage and cauliflower were not affected by the application method (Table 8 ). Brussels sprouts yield from plants supplied with the chemical fertilizer was significantly higher than the yield from plants supplied with fish silage; however, there were no yield differences between fertilizer sources for broccoli, cabbage and cauliflower. For the 1986-87 seasons, the application schedule (Table 9) for the liquid
184
C.R. BLATT
TABLE 9 Fertilizer treatments applied to four transplanted vegetables in 1986 and 1987 Treatment
N (kg h a - ~)
Application method
17-17-17 Pelleted fish silage Liquid fish silage ~
150 150 100 50 100 50 150
Pre-plant Pre-plant Pre-plant Sidedress Pre-plant Sidedress Pre-plant
Fish bone meal 2 Fish bone meal 3
~Pre-plant only in 1986, pre-plant and sidedress in 1987. 2Treatment for 1986. 3Treatment for 1987.
fish silage and the fish bone meal was to apply 100 kg h a - 1 N prior to planting, followed by a sidedress of 50 kg h a - ~ N 4-6 weeks after planting. This was accomplished with the fish bone meal; however, the liquid fish silage sidedressing could not be applied with the applicator used for the pre-plant treatment in 1986. Subsequently, a liquid fertilizer injector wheel was purchased and used to inject the liquid fish silage sidedressing treatment into the soil in the 1987-88 seasons. Yields from cabbage and cauliflower plants supplied with dry fish silage were equal to yields from plants supplied the chemical fertilizer in 1986, and these were significantly higher than yields from plants supplied liquid fish silage and fish bone meal (Table 10). Also, in 1986, yields from all four vegetables receiving liquid fish silage at 100 kg ha-1 N were similar to those from plants supplied with fish bone meal at 100 kg h a N pre-plant plus 50 kg h a - 1 N sidedress. With broccoli and Brussels sprouts, the chemical fertilizer produced yields that were higher than all organic amendments (Table 10). In 1987, marketable yield and size of broccoli, Brussels sprouts, cabbage and sweet corn receiving all fish-based products were comparable with those receiving the chemical fertilizer, and overall crop yield was substantially higher on this sandy loam soil type. Marketable yield of cauliflower plants receiving the chemical fertilizer was higher than that of plants receiving dry fish silage; however, liquid fish silage and fish bone meal supported yields comparable with those from plants receiving the chemical fertilizer (Table l 0). In 1988, seaweed meal and liquid fish silage (formic + phosphoric acids) were evaluated with the chemical fertilizer and fish bone meal, each at two rates of N (Table l 1 ). Owing to a lack of crop response to N rate, N rates (75 and 150 kg ha -~ ) were combined and a treatment × source interaction was compared with the zero N treatment (Table 12 ). Of the sea-borne products, fish bone meal pro-
11.4
336 285 245 261
wt. (g)
0.45
14.0 13.2 11.6 12.2
22.2
467 401 466 504
diam. wt. ( c m ) (g)
0.57
14.5 13.7 14.5 15.5
5.5 4.4 3.5 4.1
Sprout (g)
18.85 0.29
307.8 237.5 172.6 183.4
diam. Plant (cm) (g)
1986
1986
1987
Brussels sprouts
Broccoli head
wt. = weight; diam. = diameter.
SEM (n=4, df=9)
17-17-17 DFS LFS FBM
Treatment
31.9
588 544 630 594
Plant (g)
1987
0.27
10.0 9.8 9.9 9.5 46.2
1441 1413 1131 1216
Sprout wt. (g) (g)
1986
1987
0.48
17.3 16.4 15.7 15.7 121.7
2090 2108 2078 2013
diam. wt. ( c m ) (g)
Cabbage head
0.85
16.5 18.0 16.2 15.8
14.22
344.8 373.7 287.9 266.7
diam. wt. ( c m ) (g)
1986
0.34
11.0 11.1 10.5 9.3
53.9
1339 1163 1218 1293
diam. wt. (cm) (g)
1987
Cauliflower head
0.48
13.0 12.8 12.9 12.5
diam. (cm)
24.3
324 254 264 311
wt. (g)
0.10
18.2 17.9 18.0 17.9
length (cm)
Sweet corn ear
Effect of pelleted dry fish silage (DFS), liquid fish silage (LFS), fish bone meal ( F B M ) and a chemical fertilizer (17-17-17 ) on marketable yield and size of vegetables grown in a Cornwallis loamy sand soil in 1986 and in a Somerset sandy loam soil in 1987
TABLE lO
O~
©
~ F
t" "11
>
m ".
z
r~
z t~
K
>
z
>
o
o
186
C.R. BLATT
TABLE 11 Fertilizer treatments applied to three transplanted vegetables in 1988 Treatment
N (kgha -I )
Application method
0-17-17
0 75 150 75 150 25 and 25 and 25 and 50 and 25 and
Pre-plant Pre-plant Pre-plant Pre-plant Pre-plant Pre-plant Sidedress - 2 weeks Sidedress - 5 weeks Pre-plant Sidedress - 5 weeks
17-17-17 17-17-17
Fish bone meal Fish bone meal Seaweed meal Seaweed meal Seaweed meal Liquid fish silage Liquid fish silage
50 50 50 100 50
TABLE 12 Effect of liquid fish silage ( LFS ), fish bone meal ( FBM ), seaweed meal (SWM), 0-17-17 and 17-1717 fertilizer (N rates combined) on marketable yield, size and maturity of broccoli, cabbage and cauliflower in 19881 Treatment
0-17-172 17-17-17 FBM LFS SWM SEM ( n = 8 , d f = 2 4 )
Broccoli head
Cabbage head
Cauliflower head
wt. (g)
diam. (cm)
% early harvest
wt. (g)
diam. (cm)
wt. (g)
diam. (cm)
% early
331.0 371.6 378.2 372.2 386.0
10.9 11.5 11.3 11.6 11.6
82.0 88.3 76.4 76.2 46.1
1800 2201 2133 1997 1688
17.4 18.2 18.4 17.9 16.9
913 1063 1150 1005 919
16.1 16.7 17.3 16.3 16.1
17.1 37.8 33.7 22.0 13.9
15.06
0.44
5.47
64.2
0.22
42.6
0.26
harvest
6.22
~Somerset sandy loam. 2n = 4 a n d S E = 2 SEM. wt. = weight; diam. = diameter.
duced the most consistent results across all three vegetables and marketable yield, size and early yield values were comparable to those from the chemical fertilizer (Table 12). Cabbage and cauliflower plants supplied with seaweed meal produced yields that were comparable with the 0-17-17 treatment and were significantly lower than those from plants supplied with fish bone meal and the chemical fertilizer. Broccoli and cauliflower plants receiving seaweed meal matured later than plants receiving fish bone meal and the chemical fertilizer. Broccoli was the only crop to respond equally to all N sources (Table 12). In 1989, all crops supplied with the chemical fertilizer had market-
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES
187
TABLE 13 Effect of pelleted ground-fish silage (GFS), herring silage ( HS ), fish bone meal ( F B M ) singly and in combination with blood meal ( BM ), meat meal ( M M ) , seaweed extract (SWE), 0-17-17 and 17-1717 fertilizers on marketable yield, size and maturity of broccoli, cabbage and cauliflower in 1989 j Treatment 2
0-17-17 17-17-17 FBM+BM+MM (2:1:1) FBM+BM (1:1) FBM+BM+SWE (5:4:1) FBM+MM+SWE (5:4:1) FBM GFS HS GFS+HS (1:1) SEM ( n = 4 , d f = 2 7 )
Broccoli head
Cabbage head
Cauliflower head
wt. (g)
diam. (cm)
% early harvest
wt. (g)
diam. (cm)
wt. (g)
diam. (cm)
% early harvest
314 427 348
10.6 13.2 11.3
67.0 98.4 94.3
1099 1942 1359
14.2 17.2 15.0
327 722 442
10.8 14.1 11.5
30.6 71.4 27.0
333
11.3
76.1
1412
15.4
494
12.4
51.0
319
10.8
87.6
1327
15.2
493
12.1
39.3
345
11.7
90.7
1479
15.7
465
12.0
42.5
316 356 320 317
10.7 11.6 11.1 11.1
87.4 93.5 73.6 74.8
1433 1479 1400 1535
15.4 15.8 15.0 15.9
488 480 487 489
12.3 12.2 12.0 12.2
36.9 37.1 30.4 44.2
15.8
0.39
6.06
86.1
0.31
39.6
0.39
9.37
tSomerset sandy loam. 2All N sources applied at 80 kg h a - t N. wt. = weight; diam. = diameter.
able yields and size that were significantly higher than those of the other treatments (Table 13 ). Broccoli yield from plants receiving the 0-17-17 treatment were equal to those from all the organic amendment treatments; however, for cabbage and cauliflower the majority of the organic amendments produced yields that were greater than 0-17-17 (Table 13 ). The effect of the various organic amendments on broccoli and cauliflower maturity was inconsistent when compared with the chemical fertilizer or the 0-17-17 treatments. Broccoli, cabbage and cauliflower leaf N values in plants receiving 17-17-17 were consistently higher than those in plants receiving 0-17-17; however, there were no consistent differences in leafN values between 17-17-17 and organic treatments (Table 14). Cauliflower leaf K values were variable across all treatments and also within the organic treatments (Table 14 ). Leaf nutrient values (data not shown) were not consistently affected by any fertilizer treatment over the several soil types and the vegetables grown during the 1983-88 seasons. Leaf N, P, K, Ca and Mg responses were more commonly characterized by differences between the 0-17-17 treatment and all other nutrient sources than specific differences among organic amend-
188
C.R. BLATT
TABLE 14
Effect of pelleted ground fish silage (GFS), herring silage (HS), fish bone meal ( F B M ) singly and in combination with blood meal (BM), meat meal ( M M ) and seaweed extract (SWE), 0-17-17 and 1717-17 fertilizers on broccoli, cabbage and cauliflower % leaf N, P and K Treatment
Broccoli
Cabbage
Cauliflower
N
P
K
N
P
K
N
P
K
0-17-17 17-17-17 FBM+BM+MM (2:1:1) FBM+BM (1:1) FBM+BM+SWE (5:4:1) FBM+MM+SWE (5:4:1) FBM GFS HS GFS+HS (1+1)
2.63 3.13 2.90
0.37 0.36 0.36
1.98 1.75 1.88
1.64 1.88 1.76
0.31 0.31 0.31
2.12 2.06 1.97
2.40 2.89 2.79
0.35 0.37 0.35
1.44 1.34 1.45
2.77
0.37
1.89
1.75
0.33
1.91
2.55
0.34
1.24
2.75
0.37
1.77
1.72
0.32
2.05
2.69
0.38
1.42
2.91
0.36
1.80
1.87
0.33
2.01
2.47
0.33
1.31
2.91 2.94 2.80 2.90
0.37 0.35 0.36 0.38
1.83 1.79 1.84 1.90
1.77 1.84 1.87 1.90
0.32 0.31 0.30 0.29
1.91 2.05 1.98 1.83
2.73 2.59 2.74 2.83
0.36 0.33 0.38 0.39
1.59 1.07 1.41 1.36
SEM ( n = 4 , d f = 2 7 )
0.087
0.013
0.079
0.059
0.017
0.115
0.074
0.025
0.071
ments or between the organic amendments and the chemical fertilizer. Leaf K and Mg values for all vegetables were within the sufficiency ranges established for optimum growth, and did not reflect the low K and Mg levels inherent in most fish-based products. Similarly, all other nutrient levels were within the sufficiency ranges required for optimum production and nutrient deficiency or toxicity symptoms were not evident in any experiment. DISCUSSION
Several studies (Haworth, 1961; Smith and Hadley, 1988, 1989a,b) have dealt with the application of organic and inorganic fertilizers primarily as a N source for various vegetables. Basal pre-preplant applications of P and K were added at appropriate rates based on soil tests. In the present study, the rate of N application was equivalent for all materials and each material was the sole source of applied plant nutrients. In the 1984 experiment, there was a reduction in the number of carrot and pea seedlings emerging in plots treated with dry non-pelleted fish silage compared with germination in plots receiving the chemical fertilizer, a finding similar to that of Smith and Hadley (1989b) with carrot and lettuce seedlings supplied with a material from the activated sewage process (Protox) in a soil with a moisture content above
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES
189
16%. Soil moisture was adequate for seed germination in the 1984 experiment, but the dissolution of the finely divided dry fish silage may have been rapid enough to raise the conductivity of the soil solution to a level that was detrimental to seed germination. Similar results were obtained in glasshouse germination studies with broccoli, cabbage and cauliflower using dry fish silage (C.R. Blatt, unpublished data, 1983). The fish-based amendments generally supported marketable yields comparable to those of the chemical fertilizer for the short-season transplanted crops broccoli, cabbage and cauliflower growing in a coarse-textured, low-OM loamy sand soil with no irrigation (1984-86). However, none of the fish-based amendments appeared to exhibit any slow-release characteristics on this soil type and could not support marketable yields of Brussels sprouts, a long-season transplanted crop, comparable with the chemical fertilizer during the 1985-86 seasons. Subsequent experiments were conducted on a sandy loam soil type characterized by higher OM, soil fertility and moisture-holding capacity than the previous two soils, and the fish-based amendments generally supported crop yields comparable with those of the chemical fertilizer for the 1987-88 seasons. In 1988, rate of N (75 and 150 kg h a - l ) and the 0-17-17 treatment were included as variables (Table 11 ) due to the fact that at this location the mineralizable N values at the first two experimental sites ( 1987-88 ) were higher than those at the previous two locations. Seaweed meal was included in comparison with the fish-based amendments and the chemical fertilizer as another possible ocean-based plant nutrient source. Owing to the low N content (1%), large amounts of seaweed meal had to be applied pre-plant and as sidedressings in order to achieve rates of N equivalent to the other amendments. Apparently, the rate of mineralization of seaweed meal was slower than that of the fish-based amendments with the result that the early harvest of broccoli and cauliflower was considerably less than all other N treatments (Table 12 ). Crop response was equivalent at each N rate and the fish-based amendments were comparable with the chemical fertilizer at each rate of applied N. These results differ somewhat from those of Smith and Hadley ( 1988 ) in which summer cabbage yields with Protox and feathermeal were greater at rates of N application above the optimum levels for ammonium nitrate and dried blood. The 1989 season was the only one in which plants receiving the chemical fertilizer had significantly higher plant yield and size compared with all organic treatments (Table 13). Even though soil moisture was adequate at the time of transplanting, this was the only season in which soil and air temperatures were below normal for an extended period following transplanting. Plants receiving the chemical fertilizer were observed to be further advanced in growth during this period compared with plants receiving the organic treatments. The difference in plant size persisted throughout the season in spite of warmer temperatures and irrigation, and was reflected in crop yield, with plants receiving the organic treatments responding in a manner similar
190
C.R. BLATT
TABLE 15 S u m m a r y of effects of organic amendments compared with a chemical fertilizer ( 17-17-17 ) on marketable yield of broccoli, Brussels sprouts, cabbage and cauliflower grown on several soil types Year
1983 1984 1985 1986 1986 1986 1987 1987 1987 1988 1988 1989 1989
Treatment
Dry fish silage Dry fish silage Dry fish silage Dry fish silage Liquid fish silage Fish bone meal Dry fish silage Liquid fish silage Fish bone meal Liquid fish silage Fish bone meal Dry fish silage Fish bone meal
Soil type
Berwick sl Cornwallis ls Cornwallis Is Cornwallis Is Cornwallis Is Cornwallis Is Somerset sl Somerset sl Somerset sl Somerset sl Somerset sl Somerset sl Somerset sl
Crop yield as percent of 17-17-17 Broccoli
Brussels sprouts
Cabbage
Cauliflower
77 110 94 85 73 78 86 100 108 100 102 83 74
74 77 56 59 92.5 107 101 -
95 98 98 78 84 101 99 96 91 97 76 74
99.5 68 93 108 83.5 77 87 91 96 94.5 108 66 68
sl = sandy loam. ls = loamy sand.
to those receiving the 0-17-17 treatment. These growth discrepancies are reflected, to some extent, in the leaf nutrient values, primarily N, with some of the organic treatments having lower values compared with the chemical fertilizer treatment (Table 14). The apparent deficiency of an adequate supply of plant-available N from the organic treatments was probably the result of a slow rate of mineralization under these moist cool soil conditions, a finding similar to that of Haworth ( 1961 ) with hoof and horn meal applied to summer cabbage. It is possible that the full benefit of combining the fish- and animal-based amendments was not realized due to the early growing season conditions in 1989, as there were no consistent yield differences between these treatments and the fish-only based treatments. A summary of the crop response to several of the organic amendments compared with the chemical fertilizer is given in Table 15 and it is interesting to note the consistent response of cabbage regardless of the source of organic amendment, soil type or season. With the exception of the 1989 season, the overall crop response from plants receiving the organic amendments was more consistent and more comparable with the chemical fertilizer when plants were supplied with irrigation and grown in the Somerset sandy loam soil. ACKNOWLEDGEMENTS
The author would like to take this opportunity to thank A.G. Sponagle for technical assistance, Dr. K.B. McRae for statistical analyses; B. Harnish, Nova
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES
191
Scotia Department of Agriculture and Marketing, Truro, N.S., for analyses of organic amendments; Kenney and Ross Ltd. of Port Saxon, N.S., and National Sea Products Ltd. of Lunenburg, N.S., for fish bone meal; Acadian Seaplants Ltd. of Dartmouth, N.S., for seaweed products; Char-Vale Charolais Ltd. of Windsor, N.S., for pelleted fish silage products; Scott Farms Ltd. of Canard, N.S., for animal-based products; and Casey Fisheries, Victoria Beach, N.S., in cooperation with M. Drebot, Nova Scotia Department of Fisheries, Halifax, N.S., for dry and liquid fish silage.
REFERENCES Atkinson, H.J., Giles, G.R., MacLean, A.J. and Wright, J.R., 1958. Chemical methods of soil analysis. Can. Dep. Agric. Contrib. No. 169, p. 18. Aung, L.H. and Flick, G.J., Jr., 1980. The influence of fish solubles on growth and fruiting of tomato. HortScience, 15: 32-33. Aung, L.H., Flick, G.J., Jr., Buss, G.R. and Bryan, H.H., 1981. Fish and seafood wastes as nutrients for agricultural crop fertilization. In: S. Otwell (Editor), Proceedings of the Conference on Seafood Waste Management in the 1980's. Florida Sea Grant College Rep. No. 40, pp. 275-279. Aung, L.H., Hubbard, J.B. and Flick, G.J., Jr., 1983. Mineral composition of vegetable crops fertilized with fish-soluble nutrients. J. Agric. Food Chem., 31: 1259-1262. Blatt, C.R. and Sanford, K.A., 1990. Effects on table beet of pre-plant organic and Na-amended inorganic fertilizers. Scientia Hortic., 44: 31-41. Bray, R.H., 1948. Diagnostic techniques for soils and crops. The American Potash Institute, Washington, D.C., pp. 53-86. Cann, D.B., MacDougall, J.I. and Hilchey, J.D., 1965. Soil survey of Kings County, Nova Scotia. Rep. Nova Scotia Soil Surv. 15, Truro, NS, pp. 40-64. Emino, E.R., 1981. Effectiveness offish soluble nutrients as fertilizers on container-grown plants. HortScience, 16: 338. Haworth, F., 1961. The effects of organic and inorganic nitrogen fertilizers on the yield of early potatoes, spring cabbage, leeks and summer cabbage. J. Hortic. Sci., 36:202-215. Mehlich, A., 1978. New extractant for soil test evaluation of phosphorus, potassium, magnesium, calcium, sodium, manganese and zinc. Commun. Soil Sci. Plant Anal., 9: 477-492. Payne, R.W. (Chairman), 1987. Genstat 5. Reference Manual. Clarendon Press, Oxford, 749 pp. Smith, S.R. and Hadley, P., 1988. A comparison of the effects of organic and inorganic nitrogen fertilizers on the growth response of summer cabbage (Brassica oleracea var. capitata cv. Hispi FI.). J. Hortic. Sci., 63: 615-620. Smith, S.R. and Hadley, P., 1989a. A comparison of organic and inorganic nitrogen fertilizers: Their nitrate-N and ammonium-N release characteristics and effects on the growth response of lettuce (Lactuca sativa L. cv. Fortune). Plant Soil, 115: 135-144. Smith, S.R. and Hadley, P., 1989b. Effects of organic and inorganic fertilizers on the seedling emergence of vegetable crops. J. Hortic. Sci., 64:581-589. Tecator, 1981. Determination of Kjeldahl nitrogen content with Kjeltec auto systems I, II, III and IV. Application Note AN30/81, pp. 1-5. Waring, S.A. and Bremner, J.M., 1964. Ammonium production in soil under water-logged conditions as an index of nitrogen availability. Nature, 201:951-952.
177
Elsevier Science Publishers B.V., Amsterdam
Comparison of several organic amendments with a chemical fertilizer for vegetable production C.R. Blatt Agriculture Canada, Research Station, Kentville, N.S. B4N l J5, Canada (Accepted 22 January 1991 )
ABSTRACT Blatt, C.R., 1991. Comparison of several organic amendments with a chemical fertilizer for vegetable production. Scientia Hortic., 47:177-19 I. Field research was conducted for seven seasons (1983-89) on three soil types comparing several organic amendments (dry and liquid fish silage, fish bone meal, blood meal, meat meal, seaweed meal, seaweed extract ) with a chemical fertilizer ( 17-17-17 ) applied to seeded beans, carrots, peas and sweet corn, and transplanted broccoli, Brussels sprouts, cabbage, cauliflower and lettuce. In most instances, amendments were compared singly with a chemical fertilizer with different rates of nitrogen (N) and methods of application studied each season. In the last season ( 1989 ), combinations of fish bone meal, blood meal, meat meal and a seaweed concentrate were compared with pelleted fish silage (ground fish and herring), fish bone meal and a chemical fertilizer. For the cropping seasons 1983-88, in the majority of comparisons, plants receiving the organic amendments produced crops of comparable yield and size to those from plants receiving the chemical fertilizer. In 1989, plants receiving the chemical fertilizer had significantly higher yields than plants receiving any of the organic treatments. Soil and leaf nutrient values were not consistently affected by the soil type, fertilizer material, rate of N or method of application. Keywords: blood meal; fish bone meal; fish silage; meat meal; organic amending; seaweed products; vegetables.
INTRODUCTION
Research with fish waste products has dealt primarily with the addition of liquid fish soluble nutrients (FSN) as a soil drench or a dilute foliar spray to various crops grown in greenhouse sand culture and field plots (Aung and Flick, 1980; Aung et al., 1981; Emino, 1981 ). Mineral analyses of the edible portion of several vegetable crops grown under greenhouse conditions showed that plants fertilized with FSN exhibited either no heavy metal accumulation or no excessive heavy metal accumulation compared with plants fertilized with standard Hoagland nutrient solution (Aung et al., 1983 ). Fish solubles have been used in chemical liquid fertilizer formulations for growing house,
178
C.R. BLATT
garden and glasshouse plants. Recently, Blatt and Sanford (1990) reported that fish bone meal and liquid fish silage were suitable alternatives to a chemical fertilizer for the production of field-grown red beets and that there were no significant differences in the flavour of the beetroots due to the source of plant nutrients. Glasshouse trials (C.R. Blatt, unpublished data, 1983 ) with transplanted vegetables indicated a possible benefit from a pre-plant application of dry fish silage. Although home garden and glasshouse crops could utilize a portion of the fish waste produced, there is a larger proportion that is unused by agriculture and could potentially be an alternate source of plant nutrients if the economics of manufacture and transportation were found to be competitive with chemical fertilizers. In the Atlantic region, one of the larger volume fish waste products is fish silage which, when properly treated, can be stored and subsequently used as a liquid or dry source of plant nutrients. Other products that could potentially be sources of plant nutrients include fish bone meal, seaweed meal, seaweed concentrate, blood meal and meat meal. The objective of the present study was to compare these organic amendments with a chemical fertilizer for the production of vegetable crops. MATERIALS AND METHODS - - Three soil types (Cann et al., 1965 ) were utilized during the course of these experiments (Table 1 ). Soil nutrient values are given as a range over all replicates and over all sites where a soil type was used for more than one season. In each experiment, soil samples (0-15 cm depth) were taken from each plot during the growing season and analysed for pH ( 1 : 1 soil: water);
Soils.
TABLE 1 Soil analyses of three soil types in which vegetables were grown when comparing several organic amendments with a chemical fertilizer Soil type
Crop season
pH
OM (%)
N~ ( k g h a -~)
Ca (kgha -~)
Mg (kgha - l )
K (kgha -~)
Berwick sandy loam
1983
5.5-5.6
5.0-7.5
45-50
1350-1440
490-510
160
Cornwallis loamy sand
1984, 1985, 1986
5.6-6.1
2.0-4.0
45-55
1300-1930
180-210
120-160
260-350
Somerset sandyloam
1987, 1988, 1989
6.0-6.5
4.0-6.0
35-70
2016-3810
535-670
170-350
560-780
Mineralizable N as NH4N.
P (kgha -~) 25- 50
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES
| 79
organic matter (OM) (K2Cr207; Atkinson et al., 1958 ); Bray #2 phosphorus (P) (Bray, 1948 ) using the molybdovanadate complex for colour development; and extractable calcium (Ca), magnesium (Mg) and potassium (K) (Mehlich, 1978 ) using atomic absorption spectrometry. Mineralizable nitrogen (N) (Waring and Bremner, 1964) was determined on a representative soil sample (0-15 cm depth ) from each soil type in an attempt to characterize the potential soil N status. Crops and crop management. - - Vegetables grown included broccoli ( Brassica oleracea L., Botrytis group), Brussels sprouts (Brassica oleracea, Gemmifera group), cabbage (Brassica oleracea L., Capitata group), cauliflower (Brassica oleracea L., Botrytis group ), lettuce (Lactuca sativa), peas (Pisum sativum ), yellow beans (Phaseolus vulgar&), carrots (Daucus carota var. sativus) and sweet corn (Zea mays L.). Several vegetables were grown on each of the soil types during each cropping season; however broccoli, cabbage and cauliflower were standard crops over all soil types. Crops grown each season were: 1983 - broccoli, cabbage, cauliflower; 1984 - broccoli, cauliflower, lettuce, peas, beans, carrots; 1985 and 1986 - broccoli, Brussels sprouts, cabbage, cauliflower; 1987 - broccoli, Brussels sprouts, cabbage, cauliflower, sweet corn; 1988 and 1989 - broccoli, cabbage, cauliflower. All crops were grown in single-row plots, 4 × 0.9 m, with 0.4 m in-row spacing between transplants and standard seeding rates used for seeded crops. For all transplant experiments, the first and last plants in each plot were guard or non-record plants. Yield data included total plant top weight (kg) per plot for beans, carrots and peas, and marketable yield (g) and size (cm) per plant for transplanted crops and sweet corn. Percentages of early yield are recorded for crops in which treatment affected maturity. Recommended pesticides were applied as needed and hand cultivation was used for incorporating dry material sidedressings and weed control. Irrigation was applied during the 198789 seasons. A representative leaf sample was taken from each plot and consisted of the most recently mature fully expanded leaves. Samples were dried at 70°C and ground in a Wiley mill with sub-samples subjected to a HNO3HCIO4-H2SO4 digestion for total P, K, Ca and Mg. Total N was determined on separate sub-samples using an automated semi-micro Kjeldahl procedure (Tecator, 1981 ). K, Ca and Mg were determined on an atomic absorption spectrophotometer, and P was analysed colorimetrically using the molybdovanadate complex. Fertilizer and amendments. - - All dry pre-plant treatments were applied by hand and mechanically incorporated 7-10 days prior to planting; sidedressings were applied by hand 4-6 weeks after planting. Liquid pre-plant treatments were applied with a large watering container and sidedressings were applied by a tractor-mounted liquid applicator. 17-17-17 is a standard vege-
180
C.R. BLATT
table fertilizer and is applied commercially pre-plant at rates of N up to 150 kg ha -~. The 0-17-17 formulation was fabricated from concentrated superphosphate (46% P205 ) and KC1 (60% K:O ), and applied to equivalent rates of P and K to the 17-17-17 as an N control. Fish silage is a product of the groundfish industry and was prepared by grinding groundfish (cod, etc. ) offal and then adding formic acid (2% by wet weight) that enhances digestion and contributes to extended storage by increasing silage acidity. In 1988, silage was prepared with phosphoric and formic acids (each at 2% by weight) and strained in order to provide a product that could be applied with an ordinary farm sprayer. The nutrient content of the dry and liquid (formic acid ) silages that were used is presented in Tables 2 and 3, respectively. In subsequent experiments with dry fish silage ( 1984, etc. ), the product supplied was a combination of groundfish species with a nutrient analysis similar to the cod + perch mixture (Table 2 ). Powdered fish silage was pelleted using a dry pelleting process and used as an amendment in the 1985-87 seasons. Fish bone meal was derived as a by-product of the fish meal process utilizing fresh fish with the fish bone being extracted from the meal and ground prior to treatment application (Table 4). Blood meal and meat meal are byproducts of a local poultry rendering plant and these were blended together TABLE 2
Nutrient analyses of dry fish silage (non-pelleted), crabmeal and a combination of cod silage and crabmeal applied to vegetables in 1983 Treatment Cod Cod+perch Crabmeal Cod + crabmeal (4:1)
N (%)
P (%)
K (%)
Ca (%)
Mg (%)
Fe
Mn
Cu
Zn
B
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
9.8 10.2 3.6
5.0 4.4 1.5
0.8 1.0 0.25
6.4 5.6 16.6
0.15 0.14 0.95
65 59 193
10 7 240
6 3 37
51 52 85
T
9.0
4.3
0.75
8.7
0.32
115
64
12
59
7.3 14.3
TABLE 3
Nutrient analysis (FW basis) of liquid fish silage applied to vegetables in 1986, 1987 and 1988 Nutrient
%
Nutrient
ppm
N P K Ca Mg Dry matter
1-3 0.4-2.6 0.4 1.0 0.1 20 - 6 0
Fe Mn Cu Zn
4 -8 0.5-3.0 0.5-1.0 1 -6
4.7
181
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES TABLE 4
Nutrient analysis of dry fish bone meal applied to vegetables in 1986-1989 Nutrient
%
Nutrient
ppm
N P K Ca Mg Na
6 -10 5 -9 0.1 11 -18 0.5 1.0
B Fe Mn Cu Zn
5-20 500-1500 25-45 20-50 100-200
TABLE5
Nutrient analyses of pelleted groundfish silage (GFS), herring silage (HS), a mixture of GFS + HS, seaweed meal (SWM) and mixtures of fish bone meal (FBM), blood meal (BM), meat meal ( MM ) and seaweed extract (SWE) applied to broccoli, cabbage and cauliflower in 1989 Treatment
N (%)
P (%)
K (%)
GFS ~ HS I GFS+HS (1:1) SWM FBM+BM+MM (2:1:1) FBM+BM (1:1) FBM+BM+SWE (5:4:1) FBM+MM+SWE (5:4:1)
1.8 2.3 2.0
0.4 0.4 0.4
0.4 0.5 0.5
0.7 8.2
0.1 4.6
9.4
Ca (%)
Mg (%)
Na (%)
Fe (ppm)
Mn (ppm)
Cu (ppm)
Zn (ppm)
B (ppm)
0.7 3.9 0.5 4.8 0.6 4.3
0.2 0.2 0.2
343 613 418
33 42 37
6.0 5.9 5.3
31 42 37
62 74 69
1.9 0.8
1.3 0.8 8.4 0.2
1.0
135 392
28 7.0
1.5 4.5
33 59
91 37
5.2
1.0
9.6 0.2
1.2
722
9.0
8.1
53
25
7.8
5.9
2.9
10.2 0.3
1.6
581
10.0
9.2
56
23
7.9
5.1
2.5
8.6 0.2
1.3
206
7.8
7.7
73
18
~Dry matter ranged from 49 to 62%.
with fish bone meal and a seaweed extract in various ratios, and applied preplant (Table 5). Seaweed meal (Table 5 ) was produced by drying and grinding rockweed (Ascophyllum nodosum) and an extraction procedure was used to prepare seaweed extract. Groundfish and herring silages (Table 5 ) applied in 1989 were prepared with formic acid and then subjected to a wet pelleting process (patent pending). All organic amendments used singly and in combination were analysed for their nutrient composition by the chemistry laboratory of the Soils and Crops Branch, Nova Scotia Department of Agriculture and Marketing. Nitrogen in all the dry products was determined on a Leco automated Dumas System and in liquid fish silage by a modified Kjeldahl method
182
C.R. BLATT
following wet digestion. All other nutrients were determined with an inductively coupled argon plasma unit. Each experiment was conducted with four replications and data were analysed as a randomized complete block design with field replication treated as a block. In 1983-86, rows of different crops were nested within plots. In 1987-89, crops were planted in different areas within the same field with each set out as a randomized complete block. Comparisons among treatments were made using orthogonal contrasts or polynomial regressions. All calculations were made using Genstat 5 procedures (Payne, 1987).
Statistical
analysis.
--
RESULTS
The 1983 field trial was conducted on a sandy loam soil (Table 1 ) with soil pH, K and P levels initially lower than the average values found in a productive vegetable soil. No significant yield differences were evident when cabbage and cauliflower yield and broccoli head size data from plants receiving the chemical fertilizer were compared with values from plants receiving any amendment (Table 6). When supplied at an equivalent rate of pre-plant N (150 kg ha -1), only cod silage and the cod+crabmeal combination supported marketable yields of broccoli that were similar to the yield from plants receiving the chemical fertilizer. The rate of pre-plant N had little effect on yield and size. The 1984-86 trials were conducted on a Cornwallis loamy sand soil characterized by rapid internal drainage and low soil K and OM. Yields and head TABLE6 Effect of dry fish silage (non-pelleted) and a chemical fertilizer ( 17-17-17 ) on marketable yield and size of broccoli, cabbage and cauliflower in 1983 ~ Treatment
17-17-17 Cod Cod Cod+perch Cod+perch C o d + crabmeal (4:1) SEM ( n = 4 , d f = 15) ~Berwick sandy loam. wt. = weight.
N ( k g h a -1 )
150 75 150 75 150 150
Broccoli head
Cabbage head
Cauliflower head
wt. (g)
diameter (cm)
wt. (g)
diameter (cm)
wt. (g)
diameter (cm)
637 398 501 434 426 555
14.7 12.0 13.8 12.4 12.0 13.9
1305 1149 1218 1068 1291 1207
14.8 14.3 14.8 14.1 14.9 14.3
717 617 637 830 662 842
16.7 15.5 15.4 17.9 15.5 17.4
56.3
0.94
103.9
0.50
119.6
0.97
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES
18 3
TABLE 7 Effect of dry fish silage (non-pelleted) and a chemical fertilizer (17-17-17) on marketable yields of beans, carrots, peas, broccoli, cauliflower and lettuce in 1984 ~ Treatment 2
17-17-17 Fish silage SEM (n=4, df=3)
Bean
3944 3200 390.9
Carrot (g per plot)
Peas
9489 7173
394 162
392.8
53.9
Broccoli head
Cauliflower head
Lettuce head
wt. (g)
diameter (cm)
wt. (g)
diameter (cm)
wt. (g)
diameter (cm)
398 439
16.0 16.5
402 275
10.2 8.9
429 508
10.5 10.9
28.6
0.87
72.8
0.92
16.9
0.24
~Cornwallis loamy sand. 2Total N applied to seeded crops = 100 kg h a - ~; total N applied to transplanted crops = 150 kg h a - ~. wt. = weight. TABLE 8 Effect of dry fish silage (pelleted) and a chemical fertilizer ( 17-17-17 ), applied by two methods, on marketable yields (g per plant) of broccoli, Brussels sprouts, cabbage and cauliflower in 19851 Broccoli
Brussels sprouts
Cabbage
Cauliflower
Application method 2 Single Split
516 543
482 451
1671 1652
794 701
Treatment 17-17-17 Fish silage
546 513
536 396
1677 1646
773 722
SEM ( n = 8 , d f = 9 )
28.8
33.2
74.2
36.3
~Cornwallis loamy sand. :Single= 150 kg ha-1 N broadcast pre-plant. Split = 100 kg ha-~ N broadcast pre-plant plus 50 kg h a - ~N 4-6 weeks after planting.
size of the three transplanted vegetables were not significantly affected by fertilizer source when each vegetable was supplied with N at 150 kg h a broadcast pre-plant and incorporated (Table 7). Fish silage reduced germination in the carrot and pea plots, and led to a significant yield difference between fertilizer sources (Table 7 ). Marketable yields of broccoli, Brussels sprouts, cabbage and cauliflower were not affected by the application method (Table 8 ). Brussels sprouts yield from plants supplied with the chemical fertilizer was significantly higher than the yield from plants supplied with fish silage; however, there were no yield differences between fertilizer sources for broccoli, cabbage and cauliflower. For the 1986-87 seasons, the application schedule (Table 9) for the liquid
184
C.R. BLATT
TABLE 9 Fertilizer treatments applied to four transplanted vegetables in 1986 and 1987 Treatment
N (kg h a - ~)
Application method
17-17-17 Pelleted fish silage Liquid fish silage ~
150 150 100 50 100 50 150
Pre-plant Pre-plant Pre-plant Sidedress Pre-plant Sidedress Pre-plant
Fish bone meal 2 Fish bone meal 3
~Pre-plant only in 1986, pre-plant and sidedress in 1987. 2Treatment for 1986. 3Treatment for 1987.
fish silage and the fish bone meal was to apply 100 kg h a - 1 N prior to planting, followed by a sidedress of 50 kg h a - ~ N 4-6 weeks after planting. This was accomplished with the fish bone meal; however, the liquid fish silage sidedressing could not be applied with the applicator used for the pre-plant treatment in 1986. Subsequently, a liquid fertilizer injector wheel was purchased and used to inject the liquid fish silage sidedressing treatment into the soil in the 1987-88 seasons. Yields from cabbage and cauliflower plants supplied with dry fish silage were equal to yields from plants supplied the chemical fertilizer in 1986, and these were significantly higher than yields from plants supplied liquid fish silage and fish bone meal (Table 10). Also, in 1986, yields from all four vegetables receiving liquid fish silage at 100 kg ha-1 N were similar to those from plants supplied with fish bone meal at 100 kg h a N pre-plant plus 50 kg h a - 1 N sidedress. With broccoli and Brussels sprouts, the chemical fertilizer produced yields that were higher than all organic amendments (Table 10). In 1987, marketable yield and size of broccoli, Brussels sprouts, cabbage and sweet corn receiving all fish-based products were comparable with those receiving the chemical fertilizer, and overall crop yield was substantially higher on this sandy loam soil type. Marketable yield of cauliflower plants receiving the chemical fertilizer was higher than that of plants receiving dry fish silage; however, liquid fish silage and fish bone meal supported yields comparable with those from plants receiving the chemical fertilizer (Table l 0). In 1988, seaweed meal and liquid fish silage (formic + phosphoric acids) were evaluated with the chemical fertilizer and fish bone meal, each at two rates of N (Table l 1 ). Owing to a lack of crop response to N rate, N rates (75 and 150 kg ha -~ ) were combined and a treatment × source interaction was compared with the zero N treatment (Table 12 ). Of the sea-borne products, fish bone meal pro-
11.4
336 285 245 261
wt. (g)
0.45
14.0 13.2 11.6 12.2
22.2
467 401 466 504
diam. wt. ( c m ) (g)
0.57
14.5 13.7 14.5 15.5
5.5 4.4 3.5 4.1
Sprout (g)
18.85 0.29
307.8 237.5 172.6 183.4
diam. Plant (cm) (g)
1986
1986
1987
Brussels sprouts
Broccoli head
wt. = weight; diam. = diameter.
SEM (n=4, df=9)
17-17-17 DFS LFS FBM
Treatment
31.9
588 544 630 594
Plant (g)
1987
0.27
10.0 9.8 9.9 9.5 46.2
1441 1413 1131 1216
Sprout wt. (g) (g)
1986
1987
0.48
17.3 16.4 15.7 15.7 121.7
2090 2108 2078 2013
diam. wt. ( c m ) (g)
Cabbage head
0.85
16.5 18.0 16.2 15.8
14.22
344.8 373.7 287.9 266.7
diam. wt. ( c m ) (g)
1986
0.34
11.0 11.1 10.5 9.3
53.9
1339 1163 1218 1293
diam. wt. (cm) (g)
1987
Cauliflower head
0.48
13.0 12.8 12.9 12.5
diam. (cm)
24.3
324 254 264 311
wt. (g)
0.10
18.2 17.9 18.0 17.9
length (cm)
Sweet corn ear
Effect of pelleted dry fish silage (DFS), liquid fish silage (LFS), fish bone meal ( F B M ) and a chemical fertilizer (17-17-17 ) on marketable yield and size of vegetables grown in a Cornwallis loamy sand soil in 1986 and in a Somerset sandy loam soil in 1987
TABLE lO
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186
C.R. BLATT
TABLE 11 Fertilizer treatments applied to three transplanted vegetables in 1988 Treatment
N (kgha -I )
Application method
0-17-17
0 75 150 75 150 25 and 25 and 25 and 50 and 25 and
Pre-plant Pre-plant Pre-plant Pre-plant Pre-plant Pre-plant Sidedress - 2 weeks Sidedress - 5 weeks Pre-plant Sidedress - 5 weeks
17-17-17 17-17-17
Fish bone meal Fish bone meal Seaweed meal Seaweed meal Seaweed meal Liquid fish silage Liquid fish silage
50 50 50 100 50
TABLE 12 Effect of liquid fish silage ( LFS ), fish bone meal ( FBM ), seaweed meal (SWM), 0-17-17 and 17-1717 fertilizer (N rates combined) on marketable yield, size and maturity of broccoli, cabbage and cauliflower in 19881 Treatment
0-17-172 17-17-17 FBM LFS SWM SEM ( n = 8 , d f = 2 4 )
Broccoli head
Cabbage head
Cauliflower head
wt. (g)
diam. (cm)
% early harvest
wt. (g)
diam. (cm)
wt. (g)
diam. (cm)
% early
331.0 371.6 378.2 372.2 386.0
10.9 11.5 11.3 11.6 11.6
82.0 88.3 76.4 76.2 46.1
1800 2201 2133 1997 1688
17.4 18.2 18.4 17.9 16.9
913 1063 1150 1005 919
16.1 16.7 17.3 16.3 16.1
17.1 37.8 33.7 22.0 13.9
15.06
0.44
5.47
64.2
0.22
42.6
0.26
harvest
6.22
~Somerset sandy loam. 2n = 4 a n d S E = 2 SEM. wt. = weight; diam. = diameter.
duced the most consistent results across all three vegetables and marketable yield, size and early yield values were comparable to those from the chemical fertilizer (Table 12). Cabbage and cauliflower plants supplied with seaweed meal produced yields that were comparable with the 0-17-17 treatment and were significantly lower than those from plants supplied with fish bone meal and the chemical fertilizer. Broccoli and cauliflower plants receiving seaweed meal matured later than plants receiving fish bone meal and the chemical fertilizer. Broccoli was the only crop to respond equally to all N sources (Table 12). In 1989, all crops supplied with the chemical fertilizer had market-
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES
187
TABLE 13 Effect of pelleted ground-fish silage (GFS), herring silage ( HS ), fish bone meal ( F B M ) singly and in combination with blood meal ( BM ), meat meal ( M M ) , seaweed extract (SWE), 0-17-17 and 17-1717 fertilizers on marketable yield, size and maturity of broccoli, cabbage and cauliflower in 1989 j Treatment 2
0-17-17 17-17-17 FBM+BM+MM (2:1:1) FBM+BM (1:1) FBM+BM+SWE (5:4:1) FBM+MM+SWE (5:4:1) FBM GFS HS GFS+HS (1:1) SEM ( n = 4 , d f = 2 7 )
Broccoli head
Cabbage head
Cauliflower head
wt. (g)
diam. (cm)
% early harvest
wt. (g)
diam. (cm)
wt. (g)
diam. (cm)
% early harvest
314 427 348
10.6 13.2 11.3
67.0 98.4 94.3
1099 1942 1359
14.2 17.2 15.0
327 722 442
10.8 14.1 11.5
30.6 71.4 27.0
333
11.3
76.1
1412
15.4
494
12.4
51.0
319
10.8
87.6
1327
15.2
493
12.1
39.3
345
11.7
90.7
1479
15.7
465
12.0
42.5
316 356 320 317
10.7 11.6 11.1 11.1
87.4 93.5 73.6 74.8
1433 1479 1400 1535
15.4 15.8 15.0 15.9
488 480 487 489
12.3 12.2 12.0 12.2
36.9 37.1 30.4 44.2
15.8
0.39
6.06
86.1
0.31
39.6
0.39
9.37
tSomerset sandy loam. 2All N sources applied at 80 kg h a - t N. wt. = weight; diam. = diameter.
able yields and size that were significantly higher than those of the other treatments (Table 13 ). Broccoli yield from plants receiving the 0-17-17 treatment were equal to those from all the organic amendment treatments; however, for cabbage and cauliflower the majority of the organic amendments produced yields that were greater than 0-17-17 (Table 13 ). The effect of the various organic amendments on broccoli and cauliflower maturity was inconsistent when compared with the chemical fertilizer or the 0-17-17 treatments. Broccoli, cabbage and cauliflower leaf N values in plants receiving 17-17-17 were consistently higher than those in plants receiving 0-17-17; however, there were no consistent differences in leafN values between 17-17-17 and organic treatments (Table 14). Cauliflower leaf K values were variable across all treatments and also within the organic treatments (Table 14 ). Leaf nutrient values (data not shown) were not consistently affected by any fertilizer treatment over the several soil types and the vegetables grown during the 1983-88 seasons. Leaf N, P, K, Ca and Mg responses were more commonly characterized by differences between the 0-17-17 treatment and all other nutrient sources than specific differences among organic amend-
188
C.R. BLATT
TABLE 14
Effect of pelleted ground fish silage (GFS), herring silage (HS), fish bone meal ( F B M ) singly and in combination with blood meal (BM), meat meal ( M M ) and seaweed extract (SWE), 0-17-17 and 1717-17 fertilizers on broccoli, cabbage and cauliflower % leaf N, P and K Treatment
Broccoli
Cabbage
Cauliflower
N
P
K
N
P
K
N
P
K
0-17-17 17-17-17 FBM+BM+MM (2:1:1) FBM+BM (1:1) FBM+BM+SWE (5:4:1) FBM+MM+SWE (5:4:1) FBM GFS HS GFS+HS (1+1)
2.63 3.13 2.90
0.37 0.36 0.36
1.98 1.75 1.88
1.64 1.88 1.76
0.31 0.31 0.31
2.12 2.06 1.97
2.40 2.89 2.79
0.35 0.37 0.35
1.44 1.34 1.45
2.77
0.37
1.89
1.75
0.33
1.91
2.55
0.34
1.24
2.75
0.37
1.77
1.72
0.32
2.05
2.69
0.38
1.42
2.91
0.36
1.80
1.87
0.33
2.01
2.47
0.33
1.31
2.91 2.94 2.80 2.90
0.37 0.35 0.36 0.38
1.83 1.79 1.84 1.90
1.77 1.84 1.87 1.90
0.32 0.31 0.30 0.29
1.91 2.05 1.98 1.83
2.73 2.59 2.74 2.83
0.36 0.33 0.38 0.39
1.59 1.07 1.41 1.36
SEM ( n = 4 , d f = 2 7 )
0.087
0.013
0.079
0.059
0.017
0.115
0.074
0.025
0.071
ments or between the organic amendments and the chemical fertilizer. Leaf K and Mg values for all vegetables were within the sufficiency ranges established for optimum growth, and did not reflect the low K and Mg levels inherent in most fish-based products. Similarly, all other nutrient levels were within the sufficiency ranges required for optimum production and nutrient deficiency or toxicity symptoms were not evident in any experiment. DISCUSSION
Several studies (Haworth, 1961; Smith and Hadley, 1988, 1989a,b) have dealt with the application of organic and inorganic fertilizers primarily as a N source for various vegetables. Basal pre-preplant applications of P and K were added at appropriate rates based on soil tests. In the present study, the rate of N application was equivalent for all materials and each material was the sole source of applied plant nutrients. In the 1984 experiment, there was a reduction in the number of carrot and pea seedlings emerging in plots treated with dry non-pelleted fish silage compared with germination in plots receiving the chemical fertilizer, a finding similar to that of Smith and Hadley (1989b) with carrot and lettuce seedlings supplied with a material from the activated sewage process (Protox) in a soil with a moisture content above
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES
189
16%. Soil moisture was adequate for seed germination in the 1984 experiment, but the dissolution of the finely divided dry fish silage may have been rapid enough to raise the conductivity of the soil solution to a level that was detrimental to seed germination. Similar results were obtained in glasshouse germination studies with broccoli, cabbage and cauliflower using dry fish silage (C.R. Blatt, unpublished data, 1983). The fish-based amendments generally supported marketable yields comparable to those of the chemical fertilizer for the short-season transplanted crops broccoli, cabbage and cauliflower growing in a coarse-textured, low-OM loamy sand soil with no irrigation (1984-86). However, none of the fish-based amendments appeared to exhibit any slow-release characteristics on this soil type and could not support marketable yields of Brussels sprouts, a long-season transplanted crop, comparable with the chemical fertilizer during the 1985-86 seasons. Subsequent experiments were conducted on a sandy loam soil type characterized by higher OM, soil fertility and moisture-holding capacity than the previous two soils, and the fish-based amendments generally supported crop yields comparable with those of the chemical fertilizer for the 1987-88 seasons. In 1988, rate of N (75 and 150 kg h a - l ) and the 0-17-17 treatment were included as variables (Table 11 ) due to the fact that at this location the mineralizable N values at the first two experimental sites ( 1987-88 ) were higher than those at the previous two locations. Seaweed meal was included in comparison with the fish-based amendments and the chemical fertilizer as another possible ocean-based plant nutrient source. Owing to the low N content (1%), large amounts of seaweed meal had to be applied pre-plant and as sidedressings in order to achieve rates of N equivalent to the other amendments. Apparently, the rate of mineralization of seaweed meal was slower than that of the fish-based amendments with the result that the early harvest of broccoli and cauliflower was considerably less than all other N treatments (Table 12 ). Crop response was equivalent at each N rate and the fish-based amendments were comparable with the chemical fertilizer at each rate of applied N. These results differ somewhat from those of Smith and Hadley ( 1988 ) in which summer cabbage yields with Protox and feathermeal were greater at rates of N application above the optimum levels for ammonium nitrate and dried blood. The 1989 season was the only one in which plants receiving the chemical fertilizer had significantly higher plant yield and size compared with all organic treatments (Table 13). Even though soil moisture was adequate at the time of transplanting, this was the only season in which soil and air temperatures were below normal for an extended period following transplanting. Plants receiving the chemical fertilizer were observed to be further advanced in growth during this period compared with plants receiving the organic treatments. The difference in plant size persisted throughout the season in spite of warmer temperatures and irrigation, and was reflected in crop yield, with plants receiving the organic treatments responding in a manner similar
190
C.R. BLATT
TABLE 15 S u m m a r y of effects of organic amendments compared with a chemical fertilizer ( 17-17-17 ) on marketable yield of broccoli, Brussels sprouts, cabbage and cauliflower grown on several soil types Year
1983 1984 1985 1986 1986 1986 1987 1987 1987 1988 1988 1989 1989
Treatment
Dry fish silage Dry fish silage Dry fish silage Dry fish silage Liquid fish silage Fish bone meal Dry fish silage Liquid fish silage Fish bone meal Liquid fish silage Fish bone meal Dry fish silage Fish bone meal
Soil type
Berwick sl Cornwallis ls Cornwallis Is Cornwallis Is Cornwallis Is Cornwallis Is Somerset sl Somerset sl Somerset sl Somerset sl Somerset sl Somerset sl Somerset sl
Crop yield as percent of 17-17-17 Broccoli
Brussels sprouts
Cabbage
Cauliflower
77 110 94 85 73 78 86 100 108 100 102 83 74
74 77 56 59 92.5 107 101 -
95 98 98 78 84 101 99 96 91 97 76 74
99.5 68 93 108 83.5 77 87 91 96 94.5 108 66 68
sl = sandy loam. ls = loamy sand.
to those receiving the 0-17-17 treatment. These growth discrepancies are reflected, to some extent, in the leaf nutrient values, primarily N, with some of the organic treatments having lower values compared with the chemical fertilizer treatment (Table 14). The apparent deficiency of an adequate supply of plant-available N from the organic treatments was probably the result of a slow rate of mineralization under these moist cool soil conditions, a finding similar to that of Haworth ( 1961 ) with hoof and horn meal applied to summer cabbage. It is possible that the full benefit of combining the fish- and animal-based amendments was not realized due to the early growing season conditions in 1989, as there were no consistent yield differences between these treatments and the fish-only based treatments. A summary of the crop response to several of the organic amendments compared with the chemical fertilizer is given in Table 15 and it is interesting to note the consistent response of cabbage regardless of the source of organic amendment, soil type or season. With the exception of the 1989 season, the overall crop response from plants receiving the organic amendments was more consistent and more comparable with the chemical fertilizer when plants were supplied with irrigation and grown in the Somerset sandy loam soil. ACKNOWLEDGEMENTS
The author would like to take this opportunity to thank A.G. Sponagle for technical assistance, Dr. K.B. McRae for statistical analyses; B. Harnish, Nova
ORGANIC AMENDMENTS WITH CHEMICAL FERTILIZER FOR VEGETABLES
191
Scotia Department of Agriculture and Marketing, Truro, N.S., for analyses of organic amendments; Kenney and Ross Ltd. of Port Saxon, N.S., and National Sea Products Ltd. of Lunenburg, N.S., for fish bone meal; Acadian Seaplants Ltd. of Dartmouth, N.S., for seaweed products; Char-Vale Charolais Ltd. of Windsor, N.S., for pelleted fish silage products; Scott Farms Ltd. of Canard, N.S., for animal-based products; and Casey Fisheries, Victoria Beach, N.S., in cooperation with M. Drebot, Nova Scotia Department of Fisheries, Halifax, N.S., for dry and liquid fish silage.
REFERENCES Atkinson, H.J., Giles, G.R., MacLean, A.J. and Wright, J.R., 1958. Chemical methods of soil analysis. Can. Dep. Agric. Contrib. No. 169, p. 18. Aung, L.H. and Flick, G.J., Jr., 1980. The influence of fish solubles on growth and fruiting of tomato. HortScience, 15: 32-33. Aung, L.H., Flick, G.J., Jr., Buss, G.R. and Bryan, H.H., 1981. Fish and seafood wastes as nutrients for agricultural crop fertilization. In: S. Otwell (Editor), Proceedings of the Conference on Seafood Waste Management in the 1980's. Florida Sea Grant College Rep. No. 40, pp. 275-279. Aung, L.H., Hubbard, J.B. and Flick, G.J., Jr., 1983. Mineral composition of vegetable crops fertilized with fish-soluble nutrients. J. Agric. Food Chem., 31: 1259-1262. Blatt, C.R. and Sanford, K.A., 1990. Effects on table beet of pre-plant organic and Na-amended inorganic fertilizers. Scientia Hortic., 44: 31-41. Bray, R.H., 1948. Diagnostic techniques for soils and crops. The American Potash Institute, Washington, D.C., pp. 53-86. Cann, D.B., MacDougall, J.I. and Hilchey, J.D., 1965. Soil survey of Kings County, Nova Scotia. Rep. Nova Scotia Soil Surv. 15, Truro, NS, pp. 40-64. Emino, E.R., 1981. Effectiveness offish soluble nutrients as fertilizers on container-grown plants. HortScience, 16: 338. Haworth, F., 1961. The effects of organic and inorganic nitrogen fertilizers on the yield of early potatoes, spring cabbage, leeks and summer cabbage. J. Hortic. Sci., 36:202-215. Mehlich, A., 1978. New extractant for soil test evaluation of phosphorus, potassium, magnesium, calcium, sodium, manganese and zinc. Commun. Soil Sci. Plant Anal., 9: 477-492. Payne, R.W. (Chairman), 1987. Genstat 5. Reference Manual. Clarendon Press, Oxford, 749 pp. Smith, S.R. and Hadley, P., 1988. A comparison of the effects of organic and inorganic nitrogen fertilizers on the growth response of summer cabbage (Brassica oleracea var. capitata cv. Hispi FI.). J. Hortic. Sci., 63: 615-620. Smith, S.R. and Hadley, P., 1989a. A comparison of organic and inorganic nitrogen fertilizers: Their nitrate-N and ammonium-N release characteristics and effects on the growth response of lettuce (Lactuca sativa L. cv. Fortune). Plant Soil, 115: 135-144. Smith, S.R. and Hadley, P., 1989b. Effects of organic and inorganic fertilizers on the seedling emergence of vegetable crops. J. Hortic. Sci., 64:581-589. Tecator, 1981. Determination of Kjeldahl nitrogen content with Kjeltec auto systems I, II, III and IV. Application Note AN30/81, pp. 1-5. Waring, S.A. and Bremner, J.M., 1964. Ammonium production in soil under water-logged conditions as an index of nitrogen availability. Nature, 201:951-952.