Open Journal of Soil Science, 2012, 2, 299-311
http://dx.doi.org/10.4236/ojss.2012.23036 Published Online September 2012 (http://www.SciRP.org/journal/ojss)
299
Relative Effectiveness of Various Amendments in
Improving Yield and Nutrient Uptake under Organic Crop
Production
Sukhdev S. Malhi
Agriculture and Agri-Food Canada, Melfort, Canada.
Received July 5th, 2012; revised July 8th, 2012; accepted July 19th, 2012
ABSTRACT
In organic farming, artificial/synthetic inorganic fertilizers/chemicals are not applied to increase crop yields, but ade-
quate amounts of nutrients are essential for sustainable high production from agricultural crops. Two 3-year (2008—
wheat, 2009—pea, and 2010—barley) field experiments were conducted on certified organic farms near Spalding (Dark
Brown Chernozem—Typic Haploboroll) and Star City (Gray Luvisol—Typic Haplocryalf) in northeastern Saskatche-
wan to determine the relative effectiveness of various organic amendments (compost, alfalfa pellets, wood ash, rock
phosphate, Penicillium bilaiae, MykePro, or gypsum), and intercropping of non-legume (wheat, barley) and legume
(pea) annual crops on seed yield, total biomass yield (TBY) and nutrient uptake in seed + straw of wheat, pea and barley.
In 2008, seed yield, TBY and nutrient uptake of wheat increased (but small) with compost and alfalfa pellets. In 2010,
seed yield, TBY and nutrient uptake of barley increased substantially with compost and alfalfa pellets and moderately
with wood ash. Other amendments had little or no effect on crop yield and nutrient uptake. In 2009, there was no bene-
ficial effect of any amendment on yield and nutrient uptake of pea, most likely due to fixation of N which is the most
limiting nutrient in these soils. Intercropping of wheat or barley with pea produced greater seed yield and nutrient up-
take per unit land area basis compared to wheat or barley grown as sole crops in most cases. In conclusion, our results
suggest potential benefits in improving yield and nutrient uptake of wheat and barley from compost, alfalfa pellets and
possibly wood ash, most likely by preventing deficiencies of some nutrients, especially N, lacking in these soils under
organic farming. Our findings also suggest the need for future research to determine the feasibility of rock phosphate,
Penicillium bilaiae, MykePro, gypsum or other amendments in preventing P and/or S deficiency in organic crops using
soils extremely deficient in these nutrients.
Keywords: Amendments; Barley; Nutrient Uptake; Organic; Pea; Wheat; Yield
1. Introduction
The interest and demand for organically-grown food and
fiber are increasing in Canada [1] and internationally,
because of possible high economic returns due to the
price premiums on organically-grown products [2]. In
organic farming, synthetic fertilizers/chemicals are not
allowed to prevent nutrient deficiencies and increase crop
production. However, adequate amounts of nutrients are
essential for sustainable high production from agricul-
tural crops, because any nutrient limiting in soil can
cause substantial reduction in crop yield. The availability
of plant nutrients to crops depends on crop species/culti-
var, soil type and climatic conditions. In the Canadian
Prairies, under organically farmed cropping systems most
soils are deficient in available N, many soils are low in
available P, and some soils contain insufficient amounts
of available S (mostly in the Parkland region) and avail-
able K for optimum crop growth and yield [3,4]. Re-
search comparing both organic and conventional crop-
ping systems in Saskatchewan has suggested that on soils
low in available P, long-term production of organic crops
without adding adequate amounts of P can result in the
decrease/depletion of available P in soil by removing/
mining P in seed away from the field [5]. Recent research
in Montana, USA [6] has also indicated the decrease in
nutrients in organically managed soils, resulting in poor
crop yield and produce quality. Therefore, maintaining
soil fertility is an important production issue facing or-
ganic agriculture in the semi-arid region of the Cana-
dian Prairies and elsewhere.
Because N is the most limiting/deficient nutrient in
most soils for optimum yield, organic producers usually
focus on increasing N availability and minimizing N de-

Relative Effectiveness of Various Amendments in Improving Yield and
Nutrient Uptake under Organic Crop Production
300
ficiency in soil-crop system on organic farms by growing
N-fixing legume crops for grain, forge and/or green ma-
nure in the rotations [7,8]. However, if soils are deficient
in available P, K, S or other essential nutrients, the only
alternative is to use external organic sources to prevent
these nutrient deficiencies, which can be inconvenient
and/or expensive. For example, manure/compost can
provide these nutrients to crops on organic farms, but
often there is not enough manure to apply on all farm
fields, especially in remote areas where the cost of trans-
porting manure/compost to long distances can be une-
conomical [9]. On such soils, rock phosphate fertilizer,
elemental S fertilizer, gypsum, wood ash (wood ash is a
waste product of forest industry that contains large
amounts of Ca and Mg, about 0.44% P, 4.2% K, 1% S,
and small amounts of other essential nutrients) or some
other amendments may be used to correct nutrient defi-
ciencies in organic crops.
In addition, crop yields on organic farms can be in-
creased (also called out-yielding) by intercropping non-
legume and legume annual crops together [10,11]. Out-
yielding (i.e. when the yield produced by an intercrop is
greater than the yield produced by the component crops
grown in monoculture on the same total land area) can be
calculated by using Land Equivalency Ratio (LER),
which is defined as the relative land area under sole crops
that is required to produce yields equivalent to inter-
cropping [LER = (Intercrop1/Sole Crop1) + Intercrop2/
Sole Crop2)] as described by [12]. The LER values are
used to compare growth/yield of intercrops relative to the
respective sole crops. If the LER value is greater than 1,
it indicates that out-yielding is occurring with inter-
cropping, and the intercrop is more productive than the
component crops grown as sole crops (i.e. less land re-
quirement with intercropping compared to sole crops). If
the LER is lower than 1, it suggests that there is no
out-yielding occurring with intercropping (in fact under-
yielding with intercropping), and the intercrop is less
productive than the sole crops.
The information on the efficacy of organic nutrient
sources and intercropping non-legume and legume an-
nual crops in increasing yield by preventing nutrient de-
ficiencies in crops is lacking under Canadian prairie
soil-climatic conditions, especially in the Parkland region.
The main objective of our study was to determine the
relative effectiveness of various amendments (compost,
alfalfa pellets, wood ash, rock phosphate, Penicillium
bila ia e , gypsum and MykePro), and intercropping of
non-legume (wheat, barley) and legume (pea) annual
crops on yield and nutrient uptake of wheat, pea or barley
organic crops and soil quality/fertility in northeastern
Saskatchewan. The residual effects of these amendments
on organic C and N, potentially mineralizable N (Nmin)
and available nutrients (N, P, K and S) in soil are pub-
lished in a previous paper [13], and the effects of these
amendments on crop yield and uptake of N, P, K and S in
the present study are reported in this paper.
2. Materials and Methods
Two 3-year (2008—wheat, 2009—pea, and 2010—bar-
ley) field experiments were established on certified or-
ganic farms in spring 2008 near Spalding (Dark Brown
Chernozem—Typic Haploboroll) and Star City (Gray
Luvisol—Typic Haplocryalf) in northeastern Saskatche-
wan. During the summer of 2007, the land was managed
as tilled fallow in Experiment 1 at Spalding, and as green
manure fallow in Experiment 2 at Star City. At Spalding,
the land has been under certified organic farming prac-
tice for 21 years, with barley, hard red spring wheat, oat,
fall rye, flax, lentil and pea generally grown in various
rotations including green manure and/or summer fallow.
At Star City, barley, hard red spring wheat, spelt wheat,
oat, fall rye, flax, yellow mustard, polish canola, and pea
have been usually grown in various rotations including
green manure and/or summer fallow under certified or-
ganic farming practice for 15 years. Some characteristics
of soils used in these experiments are presented in Table
1. Soil was low in available N at both sites. Based on soil
type and agroecological region, the soil was suspected to
be potentially deficient in available P in Experiment 1 at
Spalding and available S in Experiment 2 at Star City.
Precipitation in the growing season (May, June, July and
August) at the two sites from 2008 to 2010, and
long-term (30-year) average of precipitation and air
temperature in May to August at the nearest Environment
Canada Meteorological Station (AAFC Melfort Research
Farm) are presented in Table 2. The precipitation in the
2008 growing season was below average, with little pre-
cipitation in May. In 2009, the growing season precipita-
tion was near long-term average, with slightly lower than
average precipitation in May and slightly higher than
average precipitation in August. In 2010, the growing
season precipitation was much higher than average (es-
pecially in June, and also in April prior to spring), and
relatively cooler air temperatures in most summer. A
randomized complete block design was used to lay out
the treatments in four replications. Each plot was 7.5 m
long and 1.8 m wide.
In Experiment 1, the 23 treatments were: 1. Control
(no amendment), 2. Compost @ 10 Mg·ha−1, 3. Compost
@ 20 Mg·ha−1, 4. Compost @ 30 Mg·ha−1, 5. Wood ash
@ 1 Mg·ha−1, 6. Wood ash @ 2 Mg·ha−1, 7. Wood ash @
3 Mg·ha−1, 8. Rock phosphate granular @ 10 kg·P·ha−1,
9. Rock phosphate granular @ 20 kg·P·ha−1, 10. Rock
phosphate granular @ 30 kg·P·ha−1, 11 Rock phosphate
finely-ground @ 10 kg·P·ha−1, 12. Rock phosphate finely-

Relative Effectiveness of Various Amendments in Improving Yield and
Nutrient Uptake under Organic Crop Production
301
Table 1. Some characteristics of soils of field experiments in spring 2008, 2009 and 2010 at Spalding and Star City in north-
eastern Saskatchewan.
Site Year
Soil great
groupZ
Depth
(cm) Texturey pHx Organic matter (%)
Nitrate-N
(mg·kg−1)
Extractable P
(mg·kg−1)
Sulphate-S
(mg·kg−1)
Extractable
K (mg·kg−1)
Spalding 2008 Dark Brown 0 - 15 SL 7.1 2.4 8.8 8.3 3.8 141
15 - 30 3.9 3.9 2.6 99
30 - 60 2.4 2.1 2.0 82
2009 0 - 15 SL nd nd 5.2 6.3 2.6 163
15 - 30 1.6 5.4 0.6 147
30 - 60 1.8 3.7 0.1 124
2010 0 - 15 SL nd nd 3.6 7.6 2.1 184
15 - 30 0.9 5.5 1.4 141
30 - 60 0.8 4.7 0.8 121
Star City 2008 Gray luvisol 0 - 15 L 6.2 1.8 10.7 8.6 2.8 154
15 - 30 3.2 5.4 2.4 116
30 - 60 1.7 5.5 1.2 115
2009 0 - 15 L nd nd 14.0 11.8 2.3 182
15 - 30 2.2 5.2 0.6 131
30 - 60 1.4 5.8 0.3 129
2010 0 - 15 L nd nd 7.2 9.7 2.4 216
15 - 30 1.5 7.2 1.4 129
30 - 60 2.0 6.3 1.7 114
ZBased on Canadian Soil Classification System. ySL and L refer to sandy loam and loam, respectively; xnd refers to not done in 2009 and 2010, as soil
pH and organic matter do not change frequently in the absence of amendments.
Table 2. Growing season monthly and total precipitation for the four site-years, and average 30-yr average precipitation and
temperature in northeastern Saskatchewan.
Precipitation in the growing season (mm)z
Month
Spalding Star City
30-yr average
2008 2009 2010 2008 2009 2010 Precipitation (mm) Temperature (˚C)
May 15.0 10.9 103.2 6.2 21.2 66.6 45.6 9.1
June 29.0 91.8 130.0 32.0 46.6 113.2 65.8 16.9
July 90.6 67.8 51.0 118.4 75.6 63.6 75.5 18.3
August 31.2 82.0 83.0 21.6 81.6 56.8 56.8 19.6
Total 165.8 252.5 367.2 178.2 225.0 300.2 243.7
zAt the nearest Environment Canada Meteorological Station (Muenster for Spalding and Melfort Research Farm for Star City).
ground @ 20 kg·P·ha−1, 13. Rock phosphate finely-
ground @ 30 kg·P·ha−1, 14. Alfalfa pellets @ 1 Mg·ha−1,
15. Alfalfa pellets @ 2 Mg·ha−1, 16. Alfalfa pellets @ 4
Mg·ha−1, 17. Alfalfa pellets @ 6 Mg·ha−1, 18. Control +
inoculate seed with Penicillium bilaiae, 19. Rock pho-
sphate granular @ 20 kg·P·ha−1 + inoculate seed with
Penicillium bilaiae, 20. Rock phosphate finely-ground @
20 kg·P·ha−1 + inoculate seed with Penicillium bilaiae,
21. Pulse (no amendment), 22. Cereal + pulse intercrop
(no amendment), and 23. MykePro.
In Experiment 2, the 21 treatments were: 1. Control (no
amendment), 2. Compost @ 10 Mg·ha−1, 3. Compost @
20 Mg·ha−1, 4. Compost @ 30 Mg·ha−1, 5. Wood ash @
1 Mg·ha−1, 6. Wood ash @ 2 Mg·ha−1, 7. Wood ash @ 3
Mg·ha−1, 8. Alfalfa pellets @ 1 Mg·ha−1, 9. Alfalfa
pellets @ 2 Mg·ha−1, 10. Alfalfa pellets @ 4 Mg·ha−1, 11.
Alfalfa pellets @ 6 Mg·ha−1, 12. Gypsum @ 10 kg·S·ha−1,
13. Gypsum @ 20 kg·S·ha−1, 14. Pulse (no amendment),
15. Cereal + pulse intercrop (no amendment), 16. Control
+ inoculate seed with Penicillium bilaiae, 17. Rock pho-

Relative Effectiveness of Various Amendments in Improving Yield and
Nutrient Uptake under Organic Crop Production
302
sphate finely-ground @ 20 kg·P·ha−1, 18. Rock phos-
phate finely-ground @ 20 kg·P·ha−1 + inoculate seed with
Penicillium bilaiae, 19. Rock phosphate granular @ 20
kg·P·ha−1, 20. Rock phosphate granular @ 20 kg·P·ha−1 +
inoculate seed with Penicillium bilaiae, and 21. Myke-Pro.
On average, compost contained 1.3% N, 0.64% P,
1.3% and 0.3% S; alfalfa pellets had 2.9% N, 0.20% P,
2.5% and 0.2% S; and wood ash contained 0.51% P,
4.5% and 1.3% S. Rock phosphate contained 7.4% P and
gypsum had 12% S. Penicillium bilaiae and MykePro do
not supply any nutrients directly to soil/plant, but these
inoculants are applied to increase the release of P from
soil and/or rock phosphate for plant uptake. The amend-
ments were broadcast on soil surface and all plots were
rotovated to a depth of about 8 cm few days prior to
seeding. Plots were seeded with a double-disc press drill
at 17.8 cm row spacing. In each plot, a 1.25 m wide by
7.0 m long strip was harvested with a plot combine to
determine seed yield. Straw yield was calculated from
two 1-m long rows, hand harvested from each plot. Sub
samples of seed and straw were oven dried (60˚C), and
analyzed for total N [14], total P [15], total K [16] and
total S [17].
The data on each parameter were subjected to analyses
of variance (ANOVA) using GLM procedure in SAS
[18]. The least significant difference at P ≤ 0.05 (LSD0.05)
was used to determine significant differences between
treatment means. For the convenience of the readers, the
results on treatments with wheat or barley intercropped
with pea, or grown as sole crops without any amendment
are reported and discussed separately. In all other amend-
ment treatments, there was only one crop in a growing
season, i.e., wheat in 2008, pea 2009, or barley in 2010.
3. Results
3.1. Experiment 1 at Spalding
3.1.1. Yield
In 2008, seed yield of wheat increased with compost and
tended to increase with alfalfa pellets at higher rates in
the first year of application (Table 3). However, appli-
cation of Penicillium bilaiae, rock phosphate fertilizer
Table 3. Seed yield and total biomass yield (TBY) of wheat (2008), pea (2009) and barley (2010) with various amendments
applied annually in spring of 2008, 2009 and 2010 at Spalding, Saskatchewan (Experiment 1).
Treatment Seed yield (kg·ha−1) TBY (kg·ha−1)
No. Amendments 2008
wheat
2009
pea
2010
barley
2008
wheat
2009
pea
2010
barley
1 Control (no amendment) 1902 3423 1253 5930 5159 4267
2 Compost @ 10 Mg·ha−1 1927 3799 2385 5669 5774 5530
3 Compost @ 20 Mg·ha−1 2146 3179 2576 6657 5314 6100
4 Compost @ 30 Mg·ha−1 2189 3326 2874 6186 5541 6747
5 Wood ash @ 1 Mg·ha−1 1743 3198 1827 5634 5081 4034
6 Wood ash @ 2 Mg·ha−1 1847 3102 1779 5606 4938 4415
7 Wood ash @ 3 Mg·ha−1 1951 3027 1820 5786 4648 4511
8 Rock phosphate granular @ 10 kg·P·ha−1 1635 3393 1601 5304 5239 3809
9 Rock phosphate granular @ 20 kg·P·ha−1 1757 3347 1526 5548 5213 3496
10 Rock phosphate granular @ 30 kg·P·ha−1 1871 3051 1659 5527 4686 4336
11 Rock phosphate finely-ground @ 10 kg·P·ha−1 1717 3177 1203 5277 4903 3743
12 Rock phosphate finely-ground @ 20 kg·P·ha−1 1815 3252 1368 5654 5025 4047
13 Rock phosphate finely-ground @ 30 kg·P·ha−1 1880 3226 1283 5943 4849 3736
14 Alfalfa pellets @ 1 Mgvha−1 1817 2968 1432 5633 4732 4100
15 Alfalfa pellets @ 2 Mg·ha−1 1954 2787 1693 5822 4515 4406
16 Alfalfa pellets @ 4 Mg·ha−1 2083 2345
2174 6271 4171 5521
17 Alfalfa pellets @ 6 Mg·ha−1 2079 1785
2128 6814 3934 4566
18 Control + Penicillium bilaiae 1823 3076 1306 5677 5013 3162
19 Rock phosphate granular @ 20 kg·P·ha−1 +
Penicillium bilaiae 1853 3372 1534 5892 4821 3560
20 Rock phosphate finely-ground @ 20 kg·P·ha−1 +
Penicillium bilaiae 1854 3150 1462 5934 4895 4144
23 MykePro 1896 3279 1412 5889 5132 3767
LSD0.05 229 534 332 754 706 1090
SEMz 80.9*** 188.7*** 117.0*** 266.5* 249.5** 383.7***
z*, ** and *** refer to significant treatment effects in ANOVA at P ≤ 0.05, P ≤ 0.01 and P ≤ 0.001, respectively.

Relative Effectiveness of Various Amendments in Improving Yield and
Nutrient Uptake under Organic Crop Production
303
without and with Penicillium bilaiae, and MykePro had
no beneficial effect on seed yield of wheat, and seed yields
were similar to the zero-amendment control. In 2009,
there was no significant increase in seed yield of pea
from the application of any amendment in the second
year of application (Table 3). In fact, seed yield of pea
decreased with increasing rate of alfalfa pellets. In 2010,
seed yield of barley increased considerably with compost,
followed by alfalfa pellets especially at higher rates, and
moderately with wood ash (Table 3). Seed yield of bar-
ley tended to increase (not significant) with granular rock
phosphate, but seed yields in finely-ground rock phos-
phate, Penicillium bilaiae and MykePro treatments were
similar to the control. Total biomass yield (TBY) usually
followed response trends similar to seed yield, with in-
crease in TBY from compost or alfalfa pellets but no
consistent increase in TBY from wood ash and other
amendments (Table 3).
3.1.2. Nu trient Uptake
In 2008, uptake of total N, K and S in seed + straw of
wheat increased with application of alfalfa pellets at high
rates (Tabl es 4 and 5). Total N, K and S uptake in seed +
straw of wheat tended to increase with application of
compost. This suggested that alfalfa pellets and possibly
compost supplied N, K and S for plant uptake in the first
year of application. In 2009, total N, K and S uptake in
seed + straw usually increased with compost, but no con-
sistent effect from other amendments (Tables 4 and 5).
In 2010, total N, K and S uptake in seed + straw in-
creased considerably with compost and moderately with
alfalfa pellets, but no effect from other amendments (Ta-
bles 4 and 5). Total P uptake in seed + straw of wheat in
2008 increased with increasing rate of alfalfa pellets and
compost, but the increases were small and not significant
(Table 4). In 2009, total P uptake in seed + straw of pea
increased with application of compost, but decreased
with increasing rate of alfalfa pellets (Table 4). In 2010,
total P uptake of barley in seed + straw in- creased con-
siderably with compost, but no consistent effect from
other amendments (Table 4).
Table 4. Total N and P uptake in seed + straw of wheat (2008), pea (2009) and barley (2010) with various amendments ap-
plied annually in spring of 2008, 2009 and 2010 at Spalding, Saskatchewan (Experiment 1).
Treatment Total N uptake in seed + straw
(kg·N·ha−1)
Total P uptake in seed + straw
(kg·P·ha−1)
No. Amendments 2008
wheat
2009
pea
2010
barley
2008
wheat
2009
pea
2010
barley
1 Control (no amendment) 51.2 127.7 41.1 10.1 13.0 10.3
2 Compost @ 10 Mg·ha−1 47.3 144.6 53.1 10.2 17.1 15.5
3 Compost @ 20 Mg·ha−1 54.3 137.8 60.9 11.8 18.0 16.0
4 Compost @ 30 Mg·ha−1 54.5 143.8 71.4 11.5 18.8 19.1
5 Wood ash @ 1 Mg·ha−1 46.0 125.2 40.1 9.6 11.2 9.9
6 Wood ash @ 2 Mg·ha−1 50.2 116.1 42.0 9.7 10.1 10.5
7 Wood ash @ 3 Mg·ha−1 50.7 113.2 41.8 9.3 10.2 11.0
8 Rock phosphate granular @ 10 kg·P·ha−1 43.3 129.9 38.4 8.6 12.4 9.4
9 Rock phosphate granular @ 20 kg·P·ha−1 45.7 126.3 36.4 8.3 11.2 8.8
10 Rock phosphate granular @ 30 kg·P·ha−1 51.6 111.2 44.7 9.3 9.3 9.3
11 Rock phosphate finely-ground @ 10 kg·P·ha−1 44.0 115.3 37.6 8.4 10.4 8.7
12 Rock phosphate finely-ground @ 20 kg·P·ha−1 50.1 118.9 42.5 9.2 10.3 9.8
13 Rock phosphate finely-ground @ 30 kg·P·ha−1 49.7 118.3 38.3 9.7 10.8 9.3
14 Alfalfa pellets @ 1 Mg·ha−1 49.8 105.2 41.1 9.3 10.1 9.3
15 Alfalfa pellets @ 2 Mg·ha−1 52.9 100.2 44.3 9.7 8.7 9.6
16 Alfalfa pellets @ 4 Mg·ha−1 62.6 89.7 56.3
10.8 8.3 11.7
17 Alfalfa pellets @ 6 Mg·ha−1 68.6 73.9 56.1 11.1 6.8 9.7
18 Control + Penicillium bilaiae 48.5 117.4 35.6 9.2 10.3 8.0
19 Rock phosphate granular @ 20 kg·P·ha−1 + Penicillium bilaiae 49.3 121.4 37.5 9.9 11.1 8.3
20 Rock phosphate finely-ground @ 20 kg·P·ha−1+
Penicillium bilaiae 51.4 118.5 43.1 9.8 10.2 9.2
23 MykePro 52.9 118.7 39.8 10.1 11.0 9.1
LSD0.05 7.3 20.8 9.2 1.6 3.2 2.5
SEMz 2.58*** 7.36*** 3.23*** 0.55*** 1.4*** 0.90***
z*** refers to significant treatment effects in ANOVA at P ≤ 0.001.

Relative Effectiveness of Various Amendments in Improving Yield and
Nutrient Uptake under Organic Crop Production
304
Table 5. Total K and S uptake in seed + straw of wheat (2008), pea (2009) and barley (2010) with various amendments ap-
plied annually in spring of 2008, 2009 and 2010 at Spalding, Saskatchewan (Experiment 1).
Treatment Total K uptake in seed + straw
(kg·K·ha−1)
Total S uptake in seed + straw
(kg·S·ha−1)
No. Amendments 2008
wheat
2009
pea
2010
barley
2008
wheat
2009
pea
2010
barley
1 Control (no amendment) 50.1 54.1 45.7 4.7 5.3 3.8
2 Compost @ 10 Mg·ha−1 47.5 74.1 62.7 4.5 9.2 5.5
3 Compost @ 20 Mg·ha−1 57.8 76.1 76.9 5.6 10.0 6.2
4 Compost @ 30 Mg·ha−1 53.0 83.7 82.1 5.4 10.6 7.3
5 Wood ash @ 1 Mg·ha−1 48.7 59.9 35.5 4.9
6.6 4.1
6 Wood ash @ 2 Mg·ha−1 48.8 60.5 42.3 5.2 6.7 4.5
7 Wood ash @ 3 Mg·ha−1 50.9 54.4 43.9 5.2 6.6 4.7
8 Rock phosphate granular @ 10 kg·P·ha−1 43.1 58.7 35.1 4.0 5.5 3.5
9 Rock phosphate granular @ 20 kg·P·ha−1 44.5 58.0 33.5 4.3 5.6 3.4
10 Rock phosphate granular @ 30 kgvP·ha−1 50.1 49.2 41.3 4.8 5.2 4.3
11 Rock phosphate finely-ground @ 10 kg·P·ha−1 42.1 51.0 37.0 3.9 5.0 3.6
12 Rock phosphate finely-ground @ 20 kg·P·ha−1 50.4 53.9 44.4 4.9 5.4 4.2
13 Rock phosphate finely-ground @ 30 kg·P·ha−1 50.6 51.0 41.9 4.8 5.2 3.6
14 Alfalfa pellets @ 1 Mg·ha−1 46.4 51.8 45.5 4.6 5.1 3.9
15 Alfalfa pellets @ 2 Mg·ha−1 47.8 49.1 48.1 4.9 4.6 4.1
16 Alfalfa pellets @ 4 Mg·ha−1 63.4 50.0 62.7 5.7 4.6 5.0
17 Alfalfa pellets @ 6 Mg·ha−1 66.0 52.9 48.3 6.6 4.2 4.5
18 Control + Penicillium bilaiae 45.4 53.3 29.4 4.7 5.4 3.2
19 Rock phosphate granular @ 20 kg·P·ha−1 +
Penicillium bilaiae 51.7 51.1 32.8 4.7 5.1 3.6
20 Rock phosphate finely-ground @ 20 kg·P·ha−1
+ Penicillium bilaiae 50.4 52.5 44.8 5.0 5.4 3.9
23 MykePro 51.1 56.4 38.1 5.1 5.6 3.8
LSD0.05 9.9 9.9 17.3 0.8 1.0 1.0
SEMz 3.50*** 3.52*** 6.11*** 0.27*** 0.34*** 0.37***
z*** refers to significant treatment effects in ANOVA at P ≤ 0.001.
3.2. Experiment 2 at Star City
3.2.1. Yield
In 2008, because of severe infestation of the experi-
mental site with wild oat, seed yield of wheat was very
low in all treatments (Table 6). Seed yield of wheat in-
creased with application of compost and alfalfa pellets in
most cases over the zero-amendment control, but there
was little or no increase in seed yield with other amend-
ments. The TBYs of wheat were moderately high, and
there was a good response of TBY to compost, followed
by alfalfa pellets and MykePro, but little or no increase
from other amendments. In 2009, due to infestation with
wild oat again, seed yields of pea were relatively low, but
TBYs were fairly high (Table 6). Both seed yield and
TBY of pea increased only with application of compost
over the control. In 2010, seed yield and TBY of barley
increased considerably with application of compost and
alfalfa pellets over the control (Table 6). There was also
an improvement in seed yield and TBY of barley (small,
but significant) with application of wood ash at high rates.
Seed yield of wild oat was higher in treatments receiving
compost and alfalfa pellets compared to the control in all
three years (data not shown).
3.2.2. Nu trient Uptake
In 2008 and 2009, total N, P, K and S uptake in seed +
straw increased with increasing rate of compost and also
increased with alfalfa pellets at high rates (Tables 7 and
8). In 2010, total N, P, K and S uptake of barley in seed +
straw increased considerably with application of compost
and alfalfa pellets over the zero-amendment control (Ta-
bles 7 and 8). There was also a tendency of increase in
total N, P, K and S uptake in seed + straw of barley

Relative Effectiveness of Various Amendments in Improving Yield and
Nutrient Uptake under Organic Crop Production
305
Table 6. Seed yield and total biomass yield (TBY) of wheat (2008), pea (2009) and barley (2010) with various amendments
applied annually in spring of 2008, 2009 and 2010 at Star City, Saskatchewan (Experiment 2).
Treatment Seed yield (kg·ha−1) TBY (kg·ha−1)
No. Amendments 2008
wheat
2009
pea
2010
barley
2008
wheat
2009
pea
2010
barley
1 Control (no amendment) 264 668 2233 3237 4893 5005
2 Compost @ 10 Mg·ha−1 435 796 3359 3905 5546 7501
3 Compost @ 20 Mg·ha−1 470 965 3570 4611 5360 8216
4 Compost @ 30 Mg·ha−1 580 1180 3671 5069 6379 8126
5 Wood ash @ 1 Mg·ha−1 305 765 2348 3897 4574 4831
6 Wood ash @ 2 Mg·ha−1 341 760 2705 3695 5009 5489
7 Wood ash @ 3 Mg·ha−1 315 791
2804 3980 5030 6230
8 Alfalfa pellets @ 1 Mg·ha−1 377 493 2663 3909 3901 5716
9 Alfalfa pellets @ 2 Mg·ha−1 340 585 2872 3837 4565 5863
10 Alfalfa pellets @ 4 Mg·ha−1 400 629 3859 4032 4782 8441
11 Alfalfa pellets @ 6 Mg·ha−1 429 726 4067 4322 5747 9577
12 Gypsum @ 10 kg·S·ha−1 391 758 2110 3855 4421 4540
13 Gypsum @ 20 kg·S·ha−1 328 633 2103 3750 4480 4685
16 Control + Penicillium bilaiae 319 691 2128 3635 3635 4638
17 Rock phosphate finely-ground @ 20 kg·P·ha−1 271 619 2170 3116 4292 4720
18 Rock phosphate finely-ground @ 20 kg·P·ha−1 +
Penicillium bilaiae 317 663 2133 3987 4639 4761
19 Rock phosphate granular @ 20 kg·P·ha−1 317 592 2323 3719 4198 5020
20 Rock phosphate granular @ 20 kg·P·ha−1 + Penicillium bilaiae347 589 2227 3775 4138 4772
21 MykePro 341 626 2202 4245 4195 4342
LSD0.05 92 221 367 834 903 941
SEMz 32.3*** 77.9*** 129.3*** 294.1* 318.4*** 331.9***
z* and *** refer to significant treatment effects in ANOVA at P ≤ 0.05 and P ≤ 0.001, respectively.
Table 7. Total N and P uptake in seed + straw of wheat (2008), pea (2009) and barley (2010) with various amendments ap-
plied annually in spring of 2008, 2009 and 2010 at Star City, Saskatchewan (Experiment 2).
Treatment Total N uptake in seed + straw
(kg·N·ha−1)
Total P uptake in seed + straw
(kg·P·ha−1)
No. Amendments 2008 wheat2009 pea2010 barley 2008 wheat 2009 pea 2010 barley
1 Control (no amendment) 34.6 46.5 57.7 4.6 6.7 13.1
2 Compost @ 10 Mg·ha−1 42.0 57.0 76.8 6.3 9.3 19.8
3 Compost @ 20 Mg·ha−1 44.0 62.5 84.4 7.9 10.5 22.4
4 Compost @ 30 Mg·ha−1 48.8 75.0 89.4 8.9 12.8 23.8
5 Wood ash @ 1 Mg·ha−1 38.9 48.9 51.1 5.2 7.3 13.8
6 Wood ash @ 2 Mg·ha−1 35.7 52.5 56.9 5.4 8.3 15.0
7 Wood ash @ 3 Mg·ha−1 41.7 51.3 64.4 6.0 7.9 16.5
8 Alfalfa pellets @ 1 Mg·ha−1 39.2 36.6 63.4 5.0 5.7 15.0
9 Alfalfa pellets @ 2 Mg·ha−1 38.1 43.3 66.9 5.7 6.6
15.3
10 Alfalfa pellets @ 4 Mg·ha−1 42.7 47.6 94.9 5.4 6.8 19.5
11 Alfalfa pellets @ 6 Mg·ha−1 49.4 62.5 114.6 6.6 7.8 21.4
12 Gypsum @ 10 kg·S·ha−1 41.1 48.0 55.1 5.7 6.4 12.7
13 Gypsum @ 20 kg·S·ha−1 36.0 43.9 53.8 4.8 6.5 13.0
16 Control + Penicillium bilaiae 34.6 40.8 53.1 4.5 5.9 13.1
17 Rock phosphate finely-ground @ 20 kg·P·ha−1 29.3 43.7 53.2 4.2 6.9 13.2
18 Rock phosphate finely-ground @ 20 kg·P·ha−1 +
Penicillium bilaiae 35.4 45.7 54.7 5.9 8.0 13.9
19 Rock phosphate granular @ 20 kg·P·ha−1 31.5 40.4 55.2 5.5 6.9 14.1
20 Rock phosphate granular @ 20 kg·P·ha−1 + Penicillium bilaiae 37.5 39.6 52.6 5.4 6.6 13.6
21 MykePro 40.4 43.2 52.4 6.2 7.0 13.1
LSD0.05 8.7 9.6 10.6 1.4 1.5 2.1
SEMz 3.07*** 3.37*** 3.73*** 0.50*** 0.52*** 0.74***
z*** refers to significant treatment effects in ANOVA at P ≤ 0.001.

Relative Effectiveness of Various Amendments in Improving Yield and
Nutrient Uptake under Organic Crop Production
306
Table 8. Total K and S uptake in seed + straw of wheat (2008), pea (2009) and barley (2010) with various amendments ap-
plied annually in spring of 2008, 2009 and 2010 at Star City, Saskatchewan (Experiment 2).
Treatment
Total K uptake in seed + straw
(kg·K·ha−1)
Total S uptake in seed + straw
(kg·S·ha−1)
No. Amendments 2008
wheat
2009
pea
2010
barley
2008
wheat
2009
pea
2010
barley
1 Control (no amendment) 48.0 77.4 40.1 3.1 5.1 5.4
2 Compost @ 10 Mg·ha−1 49.5 93.4 71.0 3.9 12.6 7.5
3 Compost @ 20 Mg·ha−1 56.0 96.9 89.0 4.7 13.3 8.5
4 Compost @ 30 Mg·ha−1 64.2 123.5 88.5 4.8 16.9 8.6
5 Wood ash @ 1 Mg·ha−1 56.3 76.5 38.2 4.5 8.5 5.1
6 Wood ash @ 2 Mg·ha−1 53.3 87.3 45.2 4.0 10.8 5.9
7 Wood ash @ 3 Mg·ha−1 54.1 87.4 54.3 4.8 11.5 6.5
8 Alfalfa pellets @ 1 Mg·ha−1 54.0 62.7 48.1 3.7 4.3 5.8
9 Alfalfa pellets @ 2 Mg·ha−1 55.3 72.6 49.8 3.4 4.6 5.9
10 Alfalfa pellets @ 4 Mg·ha−1 58.6 83.9
79.3 3.9 4.9 8.0
11 Alfalfa pellets @ 6 Mg·ha−1 59.9 111.6 109.3 4.4 5.8 9.3
12 Gypsum @ 10 kg·S·ha−1 52.2 70.9 39.2 4.1 6.4 5.4
13 Gypsum @ 20 kg·S·ha−1 50.3 74.6 38.7 3.9 8.5 5.8
16 Control + Penicillium bilaiae 46.5 55.1 37.3 3.2 3.8 4.8
17 Rock phosphate finely-ground @ 20 kg·P·ha−1 37.8 66.1 37.2 2.8 4.7 4.8
18 Rock phosphate finely-ground @ 20 kg·P·ha−1+
Penicillium bilaiae 48.0 74.9 41.7 3.2 4.8 5.0
19 Rock phosphate granular @ 20 kg·P·ha−1 47.4 66.9 42.9 3.2 4.3 5.1
20 Rock phosphate granular @ 20 kg·P·ha−1 + Penicillium bilaiae 50.3 66.4 38.2 3.6 4.8 5.0
21 MykePro 57.5 70.8 36.4 4.0 4.3 4.8
LSD0.05 17.6 18.7 12.0 1.0 2.2 0.9
SEMz 6.22 ns 6.59*** 4.22*** 0.35*** 0.79*** 0.32***
z*** and ns refer to significant treatment effects in ANOVA at P ≤ 0.001 and not significant, respectively.
with wood ash. The results suggested that N, P, K and S
in compost and alfalfa pellets became available to the
crop in all three growing seasons. There was no increase
in total N uptake in seed + straw from the application of
other amendments.
3.3. Cereal-pea Intercropping
3.3.1. Experi ment 1 a t Spalding
At Spalding, seed yield was lower with pea alone, but
greater with wheat alone than wheat-pea intercrop in
2008 (Ta ble 9). The order of seed yield was pea alone <
wheat + pea intercrop < wheat alone. The LER for
wheat-pea intercrop was 1.08 (0.62 + 0.46), suggesting
8% less land requirement for wheat-pea intercrop com-
pared to wheat or pea grown as sole crops to produce the
same seed yield. In 2009, barley alone and barley inter-
cropped with pea produced lower seed yield than the pea
alone (Table 9 ). The order of seed yield was pea alone >
barley + pea intercrop > barley alone. The LER for
barley-pea intercrop was 0.96 (0.42 + 0.54), suggesting
slightly higher land requirement for barley-pea intercrop
compared to barley or pea grown as sole crops for the
same seed yield. In 2010, seed yield of pea alone was
highest, followed by barley-pea intercrop, with the lowest
seed yield with barley alone (Table 9). The LER for bar-
ley-pea intercrop was 1.29 (0.73 + 0.56). This suggests
29% lower land requirement for barley-pea intercrop
compared to barley or pea grown as sole crops for the
same seed yield. The total biomass yield of various
crops in all three years usually showed trends similar to
seed yield (Table 9).
3.3.2. Experiment 2 at Star City
At Star City, seed yields were very low due to severe
wild oat infestation in 2008, and the order of seed yield
was pea alone < wheat + pea intercrop = wheat alone
(Table 10). The LER for wheat-pea intercrop was 1.22
(0.68 + 0.54), suggesting 22% less land requirement for
wheat-pea intercrop compared to wheat or pea grown as

Relative Effectiveness of Various Amendments in Improving Yield and
Nutrient Uptake under Organic Crop Production
307
Table 9. Seed yield and total biomass y ield (TBY - seed + straw) of wheat, barley, or pea grown as sole crops and as intercrop
(wheat-pea in 2008, and barley-pea in 2009 and 2010) without addition of any amendment in 2008, 2009 and 2010 at Spalding,
Saskatchewan (Experiment 1).
Year/treatment
Year Treatment number Sole crops versus intercrop Seed yield (kg·ha−1) TBY (kg·ha−1)
2008 1 Wheat 1902 5930
21
Pea 762 3997
22 Wheat + pea 1532 (1180 + 352) 5191
LSD
0.05 267 690
SEM 77.1*** 199.3**
2009 1 Barley 766 1359
21
Pea 3423 5159
22 Barley + pea 2167 (324 + 1843) 3595
LSD
0.05 431 581
SEM 124.6*** 167.9***
2010 1 Barley 400 1400
21
Pea 1253
4267
22 Barley + pea 990 (293+697) 3018
LSD
0.05 486 1352
SEM 123.7* 344.3*
*, ** and *** refer to significant treatment effects in ANOVA at P ≤ 0.10, P ≤ 0.05, P ≤ 0.01 and P ≤ 0.001, respectively.
Table 10. Seed yield and total biomass yield (TBY - seed + straw) of wheat, barley, or pea grown as sole crops and as inter-
crop (wheat-pea in 2008, and barley-pea in 2009 and 2010) without addition of any amendment in 2008, 2009 and 2010 at
Star City, Saskatchewan (Experiment 2).
Year/treatment
Year Treatment number Sole crops versus intercrop Seed yield (kg·ha−1) TBY (kg·ha−1)
2008 1 Wheat 264 3237
14 Pea 71 3635
15 Wheat + pea 217 (179 + 38) 3829
LSD
0.05 66 836
SEM19.2** 241.7ns
2009 1 Barley 1409 3799
14 Pea 668 4893
15 Barley + pea 886 (389+497) 4372
LSD
0.05 242 1004
SEM69.8*** 290.1●
2010 1 Barley 2233 4905
14 Pea 2399 5005
15 Barley + pea 2569 (1234+1335) 4952
LSD
0.05 859 1519
SEM 248.3ns 439 ns
•, **, *** and ns refer to significant treatment effects in ANOVA at P ≤ 0.10, P ≤ 0.01, P ≤ 0.001 and not significant, respectively.

Relative Effectiveness of Various Amendments in Improving Yield and
Nutrient Uptake under Organic Crop Production
308
sole crops to produce same seed yield. In 2009, barley
alone produced greater, but barley intercropped with pea
produced lower seed yield than the pea alone control
(Table 10). The order of seed yield was barley alone >
barley + pea intercrop > pea alone. The LER for barley-
pea intercrop was 0.93 (0.35 + 0.58), suggesting slightly
higher land requirement for barley-pea intercrop com-
pared to barley or pea grown as sole crops for the same
seed yield. In 2010, seed yield of barley-pea intercrop
tended to be higher than sole crops of barley and pea
(Table 10). The LER for barley-pea intercrop was 1.11
(0.55 + 0.56). This suggested that barley-pea intercrop
had 11% lower land requirement compared to barley or
pea grown as sole crops for the same seed yield. The
total biomass yield showed trends similar to seed yield
(Table 10).
4. Discussion
Earlier studies have shown potential beneficial effects of
both organic and mineral/inorganic amendments (that are
allowed as nutrient sources for certified organic produ-
ction), and soil activators/inoculants on crop yields, pro-
duce quality and nutrient uptake [7,19-22]. Similarly, in
our study a few amendments improved yield and nutrient
uptake of crops grown on certified organic farms, and the
results are discussed in detail by providing ex- planations
in the following paragraphs.
Previous research has indicated that composted ma-
nure is a good supplier of N, P, K, S, and other nutrients,
and is expected to increase crop yield when these nu-
trients are limiting in soil for optimum crop growth/de-
velopment [23]. Similarly, in our study, composted ma-
nure and alfalfa pellets in many cases and also wood ash
in some cases were effective in increasing crop yields in
2008 and 2010, when cereals were the test crops, and
nutrient uptake in all years regardless of crop type. The
increases in crop yields from various amendments were
most likely by preventing some nutrient deficiencies in
crops, especially N (the most yield limiting nutrient in
soil at our experimental sites), as also suggested for ma-
nure by other researchers [23]. For alfalfa pellets, it is
possible that narrow C:N ratio in plant materials of al-
falfa pellets may have supplied N and other nutrients
after mineralization [24]. In our other previous study for
the same experimental sites on residual effects of amend-
ments on soil properties [13], total and light fraction or-
ganic C and N, Nmin, and available N, P, K or S in soil
usually increased after three annual applications of com-
post, alfalfa pellets, wood ash or gypsum, depending on
the amendment and site. Therefore, the increases in up-
take of N, P, K or S in crops in the present study were
due to the fact that these amendments supplied these nu-
trients for plant uptake, most likely by increasing nutrient
availability in soil due to improvement in soil fertility
and also possibly by enhancing soil quality/tilth/health.
Crops with taproots can absorb nutrients from deeper
soil layers [25], depending on the root length [26]. How-
ever, if the surface and sub-soil layers are low in avail-
able P, then it is very difficult to increase the availability
of P on the farm site and sustain high crop production
under organic farming systems, by using deep taproot
crops in the rotation to bring P from deeper soil layers to
the surface soil for future crop use [5]. So, the only al-
ternative is to add external P source, which is acceptable
and practical under organic farming. For example, pre-
vious research has suggested the use of vesiculararbus-
cular mychorrhiza (VAM), Penicillium b ila iae , rock
phosphate, or bone meal to increase the release of P from
soil and organic P fertilizers/amendments in order to
prevent P deficiency in P-deficient soils and increase
crop yields [19,21-22,27-28]. In a field study in Sas-
katchewan, Takeda [25] did not find any benefit of rock
phosphate application on crop yield and P uptake over
two years at any of the three sites, but showed increases
in crop yield and P uptake at two sites from the applica-
tion of rock phosphate in a combination with Penicillium
bilaiae. Gleddie et al. [29] also reported positive re-
sponses to Penicillium bilaiae inoculation on soils that
were extremely deficient in P for optimum growth. How-
ever, in our study on organic farms, there was no con-
sistent significant beneficial effect of rock phosphate
and/or Penicillium bilaiae on crop yield and P uptake in
our study (with potentially P-deficient soil in Experiment
1) over three years. It is possible that our soils may not
be deficient in available P to the level to limit crop yield
under organic production, because of the possibility of
low yield potential under organic farming, as suggested
by Brandt et al. [23] when comparing organic and con-
ventional cropping systems over 12 years. We expected
increase in crop yield and/or P uptake from the finely
ground rock phosphate, because of the increase in surface
area, but it did not happen. As explained earlier, this
could be due to low yield potential of organic crops, and
possibly the finely ground rock phosphate may have also
conferred physical or chemical changes in soil, which in
turn may have affected the microbiological activities in
soil. This may have resulted in immobilization/fixation
of P from finely ground rock phosphate into the soil or-
ganic fraction and subsequently impacting plant growth
negatively on this potentially low P soil. Thus, suggest-
ing the need of future long-term investigation to deter-
mine the efficacy of rock phosphate, Penicillium bilaiae,
MykePro and other amendments in preventing deficiency
of P in organic crops on soils extremely deficient in
available P for optimum yield.
Like P, if soil is low in available S, then the only al-

Relative Effectiveness of Various Amendments in Improving Yield and
Nutrient Uptake under Organic Crop Production
309
ternative is to add external S source that can be used un-
der organic farming. Our previous research has suggested
that gypsum can be a suitable source of S to prevent S
deficiency in crops [30]. However, in our present study
on organic farm, there was little effect of gypsum used in
Experiment 2 (with potentially S-deficient soil at this site)
on crop yield and S uptake in any of the three years. It is
possible that our soil may not be deficient in available S
to the extent that can limit crop yield, because of the low
yield potential of crops in our study under organic farm-
ing and also lower S requirements of cereals than oil-
seeds. This suggests the need of future research to deter-
mine the feasibility of gypsum and other amendments
(such as granular elemental S) in preventing S deficiency
in organic crops on soils extremely deficient in available
S for optimum crop growth and yield. In our study, wood
ash increased yield of barley in both experiments in 2010,
and this may be due to the supply of P, S, or other nutria-
ents to the crop, because it contains fairly high content of
available P, S, K, Ca and Mg, but little or no N.
In 2009, there was no beneficial effect on seed yield
and/or nutrient uptake of pea from any amendment in
Experiment 1 (in fact, seed yield and nutrient uptake of
pea decreased with increasing rate of alfalfa pellets in
this experiment), and only from compost application in
Experiment 2. This was most likely that pea can fix N
from the atmospheric air for its own requirement [8,
31-33] and do not need any N (probably the most limit-
ing nutrient in soil at these sites) from external sources.
Thus, suggesting little or no increase in yield of pea from
N-supplying organic amendments, especially when soil is
adequately supplied with P, S, K, or other nutrients and
legume is the main crop. When legumes are grown in the
rotation, it is also possible that their crop residue after
decomposition may also provide N benefit to subsequent
crops for improving yield under organic farming [32,34].
In Experiment 1, we did not expect any dramatic reduc-
tion in seed yield of pea from alfalfa pellets application
treatments compared to the control. The decrease in seed
yield of pea with increasing rate of alfalfa pellets was
most likely due to the increase in wild oat infestation as
evidenced by the significant increase in seed yield of
wild oat with increasing rate of alfalfa pellets (data not
shown; seed yield of wild oat ranged from 122 to 317
kg·ha–1).
Previous research has suggested yield on organic
farms can be increased (also called out-yielding calcu-
lated as LER) by intercropping non-legume and legume
annual crops together compared to as sole crops for ce-
real-legume [10,11]. Similarly, in our study, the LER
values were greater than 1 in the cereal-pea intercrop
treatments compared to the wheat, barley, or pea as sole
crops in 2 of the 3 years. This indicates less land re-
quirement for wheat- or barley-pea intercrop compared to
wheat, barley, or pea grown as sole crops to produce the
same seed yield. This also suggests the importance of
growing intercrops in improving productivity and use
efficiency of land and soil nutrients, while sustaining
high crop production.
5. Conclusion
There was some potential benefit in improving yield and
nutrient uptake of wheat and barley from compost, alfalfa
pellets and possibly wood ash, and from intercropping
non-legume wheat or barley with legume pea. Our find-
ings suggest the need for future research to determine the
feasibility of rock phosphate, Penicillium bilaiae, Myke-
Pro, gypsum or other amendments in preventing P and/or
S deficiency in organic crops using soils extremely defi-
cient in these nutrients.
6. Acknowledgements
The author thanks Western Alfalfa for financial assi-
stance and supplying alfalfa pellets amendment for this
study, International Compost Ltd., Calgary, Alberta, for
supplying Rock Phosphate fertilizers for this study, and
D. Leach and K. Strukoff for technical help.
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