Exploring How Composts Affect the Soil’s Plant and Microbial

Community

• Review of paper from South Korea

• Analysis of paper

• Outline of my research plan for 2- year field study of compost applied to an established grass pasture

Review of paper: Effect of food waste compost on microbial population, soil

enzyme activity and lettuce growth

• Jae-Jung Lee, Ro-Dong Park, Yong-Woong Kim, Jae-Han Shim, Dong-Hyun Chae, Yo-Sup Rim, Bo-Kyoon Sohn, Tae-Hwan Kim, Kil-Yong Kim

• Department of Agricultural Chemistry, Institute of Biotechnology, Chonnam National University, South Korea, in Bioresources Technology

Introduction

• Food wastes are significant part of the waste stream in South Korea but they can be high in Na due to cooking practices

• Disposal of food wastes:– Landfilling creates groundwater problems

– Incineration – costly, environmental problems

– Feeding to animals – not healthy or practical

– Composting: good feedstock high in Nitrogen, low in salts, high moisture, but elevated levels of Na

Description of methods

• Lettuce germinated in commercial medium

• Lettuce transplanted to pot, 4 kg soil

• Amendments added to pots

• Lettuce grown 6 weeks

• Biological measurements, lettuce weights taken at end

• 9 authors!

Treatment name

Description Pounds N/A

CON

No amendments added

0

MF

Mineral fertilizer (15 kg N/10a)*

134 lbs N/A

CC

Commercial Compost

(1800 kg/10a)

107 lbs. NT/A (21 – 42.8 lbs.

NA/A)** FW0.5 Food Waste

Compost (900 kg/10a)

300 lbs. NT/A (60 – 120 lbs

lbs. NA/A FW1.0 Food Waste

Compost (1800 kg/10a)

600 lbs. NT/A (120 – 240 lbs.

NA/A) FW1.5 Food Waste

Compost (2700 kg/10a)

1200 lbs NT/A (240 – 480 lbs. NA/A)

* an a is an are, 10a = .1 ha ** Assume compost is 20 – 40 % available in year 1 *** Agronomic rate of N for lettuce is reported in litt. @ 60–80 lbs. N/A

Fig. 1. Population of fungi in rhizospheres of lettuce in pots as affected by CON, CC, MF, FW0.5, FW1.0, FW1.5.

Fig. 2. Population of bacteria in rhizospheres of lettuce in pots as affected by CON, CC, MF, FW0.5,FW1.0,FW1.5. Means with same letters are not sig. different at p<0.05 when compared by LSD, means avg. 3 reps.

Fig. 3. Microbial biomass in rhizosphere of lettuce in pots as affected by CON, CC, MF, FW0.5, FW1.0, FW1.5

Enzymes measured

• Acid phosphatase & Alkaline phosphatase– Hydrolases which catalyze the hydrolytic

cleavage of chemical bonds

• Dehydrogenase– Calalyze oxidation-reduction reactions

important in fermentation and respiration pathways

Fig. 4. Acid phosphatase activity in rhizospheres of lettuce in pots as affected by CON, CC, MF, FW0.5,FW1.0,FW1.5. Means with same letters are not sig. different at p<0.05 when compared by LSD, means avg. 3 reps.

Fig. 5. Alkaline phosphatase activity in rhizospheres of lettuce in pots as affected by CON, CC, MF, FW0.5, FW1.0, FW1.5. Means with same letters are not sig. different at p<0.05 when compared by LSD, means avg. 3 reps.

Fig. 6. Dehydrogenase activity in rhizospheres of lettuce in pots as affected by CON, CC, MF, FW0.5, Fw1.0, FW1.5.

Fig. 7. Fresh weight of lettuce in pots as affected by CON, CC, MF, FW0.5,FW1.0,FW1.5. Means with same letters are not sig. different at p<0.05 when compared by LSD, means avg. 3 reps.

Nutritional Needs of Lettuce*

• N: 60-80 #/A

• P2O5: 200#/A

• K2O: 200#/A

* From litterature, not site specific

Measurable Parameters that Indicate Quality in Compost

• CO2 evolution: maturity

• C:N

• NH4-N:NO3-N

• pH

• EC

Comparison of CC and FW

• Commercial Compost– Composted 4 months

– High C:N (38:1)

– Low Total N

– Made with a high proportion of sawdust (probably high in C, difficult to degrade)

• Food Waste Compost– Made in a lab

– Unknown additative – “Miracalous Soil Microorganisms”

– Composted for 1 year

– C:N = 12:1

Analysis of Paper

• Objective: “ Look at change in soil microbial population…” ?

• Information about soil? Silty clay from a wheat field at Ag Ext. Station – no data about initial fertility of soil to understand control with no amendments added

• No background data on population of soil microorganisms in soil used in pots

• Unclear about how rates of soil amendments xwere chosen• Description of sampling of rhizosphere soil lacking

Applying Composted Horse Manure to Grass Pasture

• Pasture planted in spring, 2004• Compost made fall, 2004 and present• Compost to be tested for quality, first batch:

C:N = 12:1• Spring 2005 application of:

– mineral fertilizer (MF) at agronomic rate based on fall soil tests and expected yield of hay (185 lbs N/A, 0 lbs. P2O5/A)

– Compost at same rate of N as MF – uncomposted horse manure at same rate of N as compost– compost tea (split plot?), 5 gal/A weekly May - September

Challenges

• To compare equivalent rates of available N among treatments

• Unknown mineralization rate of compost

• Assume manure = 50% in year 1

• Unknown effects of compost tea – may affect mineralization rates of N…

• Border effects from tea applications

More Challenges

• Little good qualatitive info available about compost tea

• How to measure “quality” of tea

• How to replicate tea every week over summer

More Challenges

• Measuring changes in soil microbial community!

• Explore effect of microbial soil life on plant response– both biomass and nutritional quality