^ (^ 3> 3 *
NFREC Res. Rpt. 94-15
CROP PRODUCTION WITH
F. M. Rhoads and S. M. Olson
NORTH FLORIDA RESEARCH AND
EDUCATION CENTER, QUINCY
Florida Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
Institute of Food and Agricultural Sciences
O r /
/ 1 2 199
University of Florida
Spent mushroom compost (SMC) has been shown to be an effective
organic fertilizer and soil amendment for growing vegetables in
north Florida. A two year experiment was conducted to determine:
the optimum amount of SMC for crop production, if there is a need
for SMC to decompose before planting a crop, and the influence of
residual SMC on crop production. Three crop species were grown
each year using three rates of SMC, 10, 20, and 40 tons acre'. Two
dates of SMC application were. included each year. For the 1993
crop, SMC was applied in October 1992 and Febuary 1993 before
planting in March 1993. In 1994, response to SMC applied in the
spring of 1993 was compared to that applied in the spring of 1994.
This provided six SMC treatments plus a non-fertilized control and
one treatment that received commercial fertilizer each year. Soil-
tests (Mehlich-1 P and K) were made on samples taken from each
treatment each year in the spring following SMC application and
incorporation. Yield was determined on all crops and plant tissue
analyses were conducted on selected crops. The optimum rate of SMC
for most crops was 20 tons acre'1. Yield response to SMC was
attributed to increased N availability because all plots contained
high levels of extractable P and K. There was no need for SMC to
decompose before planting a crop because yields were significantly
(P<0.05) higher in all crops with SMC applied immediately before
planting. Crop yields in 1994 were 21 to 57% higher with SMC
applied in the spring of 1994 in comparison with SMC applied in the
spring of 1993.
Spent mushroom compost (SMC) produced at Quincy Farms, Inc. is
an effective organic fertilizer and soil amendment for growing
vegetables in north Florida (Stephens et. al, 1989). However, the
optimum rate for crop production has not been documented.
Furthermore, response of spring planted crops to fall incorporated
SMC or response of crops planted one year after SMC incorporation
into the soil have not been evaluated. Without SMC rate response
data, it is not possible to determine the economically optimum SMC
rate as vegetable prices and SMC costs vary. Municipal solid waste
compost with a carbon:nitrogen ratio of about 40 was shown to
reduce plant growth when incorporated immediately before planting
tomatoes (Lycopersicon esculentum, Mill) but increased watermelon
[Citrullus lanatus (Thunb.) Matsum & Nakai] yield when allowed to
* decompose for three months in the soil before planting (Obreza and
Reeder, 1994). Since SMC is composted for a period of 12 wk it is
not expected to require further decomposition before planting a
Objectives of these tests were to determine: (1) optimum
amount of SMC for crop production, (2) if SMC needs to decompose
after incorporation for a few months before planting crops, and (3)
influence of soil incorporated SMC on yield of crops planted one
MATERIALS AND METHODS
Sweetcorn (Zea mays cv. Sweet Bell), tomato (cv. Colonial),
and squash (Cucurbita pepo L. var. melopepo cv. Dixie) were grown
in 1993 in plots 12 ft by 50 ft to determine crop response to SMC.
The SMC was applied broadcast and incorporated into the soil at
rates of 10, 20, and 40 tons acre"' on two dates (15 Oct 1992 and
25 Feb 1993) to provide six treatments (two application dates and
three rates of SMC). Two additional treatments were included (for
a total of eight) to compare plant response to SMC with response to
no fertilizer and also with response to 1230 lb acre"' of 13-4-13
(N-P20O-K20) commercial fertilizer. Each plot contained two raised
beds 8 in high, covered with black polyethylene mulch on 6 ft
centers. Mulch width was 3 ft and only one bed in each plot was
fumigated with methyl bromide. Sweet corn was planted in two rows
per bed 18 in apart with in-row plant spacing of 12 in after
punching holes in the mulch. Tomato and squash were planted in
single rows (one row per bed) with 20 in spacing between plants.
Squash was replanted after 6 weeks growth because herbicide for
weed control in middles caused severe phytotoxicity. The second
crop of squash showed no toxicity symptoms. A 16.7 ft section of
each bed was harvested for yield data. Nitrogen concentration in
whole plants of sweet corn at harvest was determined with micro-
kjeldahl procedures. The experimental design was a randomized
complete block for main plots with four replications and a split
plot to compare fumigated and non-fumigated treatments.
In the spring of 1994 (15 March) SMC was reapplied at previous
rates (10, 20 and 40 tons acre"') to plots that received SMC in the
fall of 1992, while plots that received SMC in the spring of 1993
did not get additional SMC. This allowed comparison between
current year and previous year SMC application dates. Crops in
* 1994 were sweet corn (cv. Sweet Bell), snap bean (Phaseolus
vulgaris L. cv. Strike) and millet (Pennisetum glaucum [L.] R.
Br., HGM-100). A no fertilizer (control) treatment was again
included along with a 1000 lb acre"' treatment of 6-8-8 (N-P205-K20)
in which sweet corn and millet received an additional 60 lb acre"'
of N, as ammonium nitrate, side band, when plants were 18 in tall,
while snap bean received only 30 lb acre'1 of N at first bloom.
Mulch and fumigation were not used in 1994. Corn and snap bean
were planted in rows 30 in apart while millet was planted in rows
8 in apart. Plot size for each crop was 15 ft by 50 ft and the
center 5 ft by 20 ft section of each plot was harvested for yield
data. The design of the experiment in 1994 was similar to that in
1993 i.e. eight treatments replicated four times in a randomized
* complete block but no split plots.
Nitrogen, phosphorus, and potassium concentrations of whole
millet plants were determined at harvest. Nitrogen was determined
by micro-kjeldahl procedures, phosphorus was determined by a
molybdenum blue method and potassium was determined with a flame
emission spectrophotometer. Determinations of P and K were made on
samples ashed at 500 OC and taken up in dilute HCl.
The SMC was dried and ashed at 500 oC and N-P-K concentrations
were determined using the same procedures as for the plant samples.
Soil samples were collected each year after spring application of
SMC and analysed in accordance with Florida Extension Service soil
testing procedures (Hanlon and Devore, 1989).
RESULTS AND DISCUSSION
Crop of 1993
Analytical tests averaged over four SMC samples showed the
following results: 62% moisture; 1.44% N, 0.40% P and 1.40% K, on
dry-matter basis. This is approximately 10 lb of N and K, and
about 3 lb of P ton-1 of SMC. Since these determinations were made
on digested and/or ashed SMC samples, they are not an estimate of
nutrient availability to crops.
Soil-test results after applying SMC (Table 1.) show that
Mehlich-1 extractable P and K were increased by SMC. Highest
extractable P was obtained with fall applied SMC at 40 tons acre"',
while highest extractable K occurred with 40 tons acre-1 of SMC
applied in the spring. However, soil-test P and K were in the high
range (high range of P = 31 to 60 mg kg'1 and high range of K = 61
to 125 mg kg-1) in all treatments, and no yield response to added
P and K was expected (Hanlon, et al., 1990). Therefore, yield
response to SMC was expected to be due to N content and influence
of organic material on soil properties.
Yield of tomato was significantly (P50.05) increased by all
rates and both application times of SMC (Table 1.). Control plots
(no SMC or commercial fertilizer) produced 42% of maximum yield,
which was 1984 boxes acre"1 (1 box = 25 lb) with 40 tons acre"' of
spring applied SMC. The yield with 20 tons acre"- of spring applied
SMC was not significantly different from the maximum yield or the
yield of the commercial fertilizer treatment. Fall applied SMC
yielded about 21% less than spring applied and the difference was
Squash yield response to SMC was almost linear for both
application dates, the average increase was 2.4 bu of squash ton'1
(1 bu = 42 lb) of fall applied SMC and 5.2 bu of squash ton'1 of
spring applied SMC (Table 1.). Average squash yield for the state
of Florida in 1992-93 was 276 bu acre"1 or about 29% greater than
the maximum yield in our test (Freie and Pugh, i994). Reduced
yields were attributed to N utilization by the first crop which was
discarded when herbicide toxicity symptoms developed. The reason
being that soil-test P and K remained in the high range following
the 1993 crop (Table 2.) and squash has a relatively high N
requirement compared to other vegetables (Geraldson and Tyler,
Average sweet corn yield with fall applied SMC was about 26%
less than spring applied SMC (Table 1.). Sweet corn yield with 20
ton acre"' of spring applied SMC was not significantly different
(P50.05) from the maximum yield of 274 crates acre"1 (1 crate = 42
lb) which was produced with commercial fertilizer.
Crop yield may vary widely in the critical concentration range
of a yield limiting nutrient but there is no significant yield
increase above the critical range (Ulrich and Hills, 1990). The
critical N concentration of whole sweet corn plants at harvest
appeared to be about 1.3% (Table 1.). This statement is supported
by the following observations: yield varied from 223 to 251 crates
acre"' (yield difference not significant) while N concentration
remained at 1.32%; where N concentration was significantly less
than 1.3%, yield was also significantly less than yield where N
concentration was near 1.3%; whereas, an N concentration of 1.78%
was significantly greater than 1.3%, but the yield increase was not
There was no response to soil fumigation with methyl bromide
by any of the crops grown in 1993.
Crop of 1994
Results from soil tests in 1994 were similar to those in 1993
and showed that both P and K were in the high range for all
treatments. Therefore, a yield response to added P and K was not
Highest snap bean yield (306 bu acre"', 1 bu = 30 lb) occurred
with commercial fertilizer and was significantly (P 0.05) higher
than the highest yield produced with SMC. The yield difference
between treatments receiving 20 and 40 tons of SMC per acre in the
spring of 1994 was not significant. Snap bean yield with SMC
applied in 1993 was 25% less than with SMC applied in 1994. Snap
bean has a more limited root system than corn for example and takes
up N more efficiently when it is banded close to the row as
compared with broadcast N. Therefore, 20 tons acre'- of SMC plus
30 lb acre"' of N as side band should produce maximum yield.
However, cost of commercial fertilizer ($97.43 acre") was less than
20 tons acre"' of SMC ($135 acre'), thus 10 ton acre"' of SMC plus
45 lb acre"' of N as side band (cost = $82.40 acre"') would be more
Sweet corn yields in 1994 were similar in magnitude to those
S of comparable treatments in 1993. For example, 40 tons acre"' of
SMC preplant produced 251 crates acre"1 in 1993 and 264 crates acre'1
in 1994 (Tables 1. and 2.). This is of interest since plastic
mulch was used in 1993 and bare ground culture was used in 1994.
Therefore, it appears that there was no advantage in using plastic
mulch for sweet corn production. Although, 40 tons acre"' of SMC
produced a significantly higher yield than 20 tons acre-1 (Table
2.), 60 lb acre'1 of N as ammonium nitrate plus 20 tons acre'1 of SMC
is expected to yield about the same as 40 tons acre'1 and would cost
considerably less ($270 versus $155 acre1'. Yield increase of
sweet corn from current year application of SMC was 5.7 crates ton'"
of SMC between 10 and 20 tons acre"' of SMC and 2.3 crates ton"'
between 20 and 40 tons acre"1 (Table 2.) Sweet corn yield in 1994
with SMC applied in 1993 was 37% less than with SMC applied in
Yield (5.8 tons acre"') of millet with 40 tons acre"' of SMC
applied in the current year was not significantly different from
the yield (5.3 tons acre"') produced with commercial fertilizer
(Table 2.) The average effect of 20 and 40 tons acre'1 of SMC on
millet yield was significantly (Ps0.10) greater than that of 10
tons acre'1 but the yield difference between 20 and 40 tons acre-1
was not significant. Therefore, 20 tons acre"1 of SMC appear to be
adequate for maximum yield of millet. Millet yield was 17%
(significant at P50.05) less with SMC applied one year before
planting compared to SMC applied a few days before planting.
Residual SMC from the previous year increased millet yield by as
much as 80% compared to the control treatment, however, the effect
of application rate was not significant.
Regression analysis showed that yield of millet was much more
dependent on N concentration than either P or K concentration. The
40 ton acre"' rate of SMC applied in 1994 supplied millet with 112
lb of N acre"1 (151 39 in control treatment) compared with 100 lb
acre"' (139 39) supplied by commercial fertilizer. The N recovery
efficiency of millet from commercial fertilizer was (100 + 120)
83%. However, the 50 lb of N acre"' (89 39) recovered from the
40 ton acre"' rate of SMC applied in 1993 shows that a considerable
amount of N was released from the SMC during the second year. The
critical range of P concentration in millet after five wk growth is
0.16 to 0.20%, while the critical range of K concentration is
1.6 to 2.0% (Kelling and Matocha, 1990). Luxury consumption of P
by millet occurred as shown by a yield of 5.0 tons acre"' with 0.22%
P and a yield of 5.3 tons acre"1 with 0.16% P (Table 2.). Increased
K concentration with increased yield was attributed to luxury
consumption because K concentration was not below the critical
range even in the control treatment. Millet planted in close rows
has a more uniform distribution of roots in the plow layer than any
of the other crops in the test and should give a more accurate
estimate of nutrient supplying characteristics of SMC.
Soil-test P was increased each year from high (31-60 mg kg')
to very high (>60 mg kg"') with 20 or 40 tons acre"' of SMC. The
immediate effect of SMC on soil-test K was to increase it from high
(61-125 mg kg-1) to very high (>125 mg kg'1) but after a few months
it dropped back into the high range.
The optimum rate of compost was 20 ton acre"' for most crops,
even where 40 tons acre"' produced the highest yield it was more
cost effective to add nitrogen from commercial fertilizer to
increase yield. In the case of snap bean which has a limited root
system, it appears that an annual application of 10 tons acre"' of
SMC plus a side band application of 30 lb of commercial N acre"'
would be satisfactory. For sweet corn, 20 tons acre"1 of SMC plus
50 lb acre"' of commercial N as a side band application appears to
be satisfactory for bare ground production practices, however, the
extra N was not necessary for mulched bed production.
There was no yield advantage for applying SMC several months
* before planting crops. This was demonstrated by observations that
SMC applied 5 or 12 months before planting crops yielded from 17 to
37% less than when applied a few days before planting. Therefore,
the need to allow SMC to decompose before planting crops was not
Since the yield response to SMC was attributed to increased N
availability it appears that satisfactory results could be obtained
if SMC is applied at the rate of 20 tons acre"1, as needed, to
maintain availability of P and K for optimum yield; and commercial
N is applied according to extension service recommendations in
years when SMC is not applied.
Freie, R. L. and N. L. Pugh. 1994. Vegetable summary 1992-1993,
Florida Agricultural Statistics. Florida Department of
Agriculture and Consumer Services, Orlando.
Geraldson, C. M. and K. B. Tyler. 1990. Plant analysis as an aid in
fertilizing vegetable crops. p. 549-562. In R. L. Westerman
(ed.) Soil testing and plant analysis. SSSA, Madison, WI.
Hanlon, E. A., G. Kidder, and B. L. McNeal. 1990. Soil, container
media, and water testing; interpretations and standardized
fertilization recommendations. Florida Coop. Extension Serv.,
Univ. of Florida, Gainesville. Circular 817. 49 pp.
Kelling, K. A. and J. E. Matocha. 1990. Plant analysis as an aid in
fertilizing forage crops. p. 603-643. In R. L. Westerman (ed.)
Soil testing and plant analysis. SSSA, Madison, WI.
Obreza, T. A. and R. K. Reeder. 1994. Municipal solid waste compost
in tomato/watermelon successional cropping. Soil Crop Sci.
Soc. Florida Proc. 53:13-19.
Steel, R. G. D., and J. H. Torrie. 1960. Principles and Procedures
of Statistics. McGraw-Hill, New York. 481 pp.
Stephens, J. M., G. C. Henry, B. F. Castro, and D. L. Bennett.
1989. Mushroom compost as a soil amendment for vegetable
gardens. Proc. Fla. State Hort. Soc. 102:108-111.
Ulrich, A., and F. J. Hills. 1990. Plant analysis as an aid in
fertilizing sugarbeet. p. 429-447. In R. L. Westerman (ed.)
Soil testing and plant analysis. SSSA, Madison, WI.
Table 1. Soil-test results; yield of tomato, squash. and sweet corn; and N
concentration of sweet corn plants at harvest in 1993 on soil
amended with spent mushroom compost (SMC).
Soil Soil-test Tomatot Squash[ Sweet cornS N-Conc. of
Treatment P K Yield Yield yield sweet corn
mg kg' tons acre" %
Control (NT) 34 61 10.4 0.4 1.6 0.94
SMC (F) 10 53 76 15.9 0.9 2.4 1.06
SMC (F) 20 61 100 15.9 1.6 3.0 0.97
SMC (F) 40 92 131 18.9 2.4 4.7 1.32
SMC (S) 10 51 120 16.8 1.6 3.4 1.06
SMC (S) 20 62 188 22.6 2.7 5.1 1.29
S SMC (S) 40 65 296 24.8 4.5 5.3 1.32
13-4-13 79 220 22.9 3.0 5.7 1.78
LSD 0. 24 51 4.3 0.7 1.0 0.23
t NT = no treatment, F = fall applied SMC, S = spring applied SMC; 10, 20, and
40 = tons acre' of SMC; 13-4-13 = 160 lb N acre", 22 lb P acre', 133 lb K acre"
$ To convert yield: to boxes of tomatoes multiply by 80, to bushels of squash
or crates of sweet corn multiply by 47.6.
Table 2. Soil-test results; yield of snap bean, sweet corn, and millet; and N, P, and K
concentration of millet in 1994 on soil amended with spent mushroom compost
Soil Soil-test Snap bean Sweet corn Millet cone. of millet
Treatment P K yields yields yield N P K
-mg kg'1- tons acre' %
Control (NT) 31 74 1.8 1.2 2.6 0.73 0.13 1.78
SMC (94) 10 53 149 3.1 3.4 4.2 0.95 0.20 2.37
SMC (94) 20 62 173 3.7 4.5 4.9 1.08 0.22 2.63
SMC (94) 40 97 306 3.3 5.5 5.8 1.30 0.23 3.09
SMC (93) 10 42 81 2.2 2.0 3.6 0.82 0.15 1.75
SMC (93) 20 40 92 2.7 3.2 4.1 0.92 0.14 1.91
SMC (93) 40 59 90 2.8 3.4 4.7 0.94 0.16 2.19
6-8-8 29 80 4.6 5.9 5.3 1.33 0.16 2.63
LSDo. 13 34 0.8 0.9 1.4 0.18 0.04 0.28
t NT = no treatment; 93 = spring application of SMC in 1993, 94 = spring application of SMC
in 1994; 10, 20, and 40 = tons acre' of SMC; 6-8-8 = 60 lb N acre-, 35 lb P acre-', and 66
lb K acre', snap bean in this treatment received 30 Ib of N acre-' as side band while sweet
corn and millet each received 60 lb of N acre'.
$ To convert yield to: bushels of snap bean multiply by 66.7, crates of sweet corn multiply
by 47.6. Millet yield is equal to dry-matter production.