View Full Table | Close Full ViewTable 1.

Systems description of historical management (1993–2005): weed control, N fertility source and rate (by crop), and soil C and N content (2008) for four systems—conventional (CO), integrated fertilizer (IF), integrated compost (IC), and organic (OR)—in a long-term crop rotation experiment located at the W.K. Kellogg Biological Station, southwest Michigan.

 
System Weed control Range of annual inorganic fertilizer N†
Annual amount of total N in compost
Soil C Soil N
Corn Soybean Wheat Corn‡ Soybean Wheat
kg N ha–1 mg kg–1
CO broadcast herbicide 90–188 0 62–90 0 0 0 7234 d§ 761 d
IF banded herbicide + row cultivator 67–161 0 62–90 0 0 0 9187 c 915 c
IC banded herbicide + row cultivator 0 0 0 100 100 11622 b 1057 b
OR rotary hoe + row cultivator 0 0 0 100 100 12944 a 1156 a
Fertilizer application rate based on presidedress N test results.
Compost application was double the rate in second-year corn.
§ Average values for soil measurements followed by the same letter are not significantly different (P < 0.05).



View Full Table | Close Full ViewTable 2.

Sources of variation and corresponding P values among systems (integrated fertilizer, integrated compost, and organic in 2006; the same plus conventional in 2007), cover (red clover vs. winter fallow), and year (2006 and 2007) for cover biomass, cover biomass N, corn biomass, corn biomass N, corn grain yield, and corn grain N. Data are from a long-term field crop experiment at the Kellogg Biological Station in southwest Michigan.

 
Source of variation P > F
Cover biomass Cover biomass N Corn biomass Corn biomass N Corn grain yield Corn grain N
System 0.0006 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001
Cover <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001
System × cover 0.3850 0.4288 0.8699 0.6885 0.9647 0.1960
Year 0.0538 0.9015 0.0882 <0.0001 0.0023 <0.0001
System × year 0.0903 0.0490 0.3989 0.0362 0.1330 0.0096
Cover × year 0.3597 0.0007 0.3220 0.0441 0.0070 0.8808
System × cover × year 0.8916 0.8166 0.9487 0.4808 0.6905 <0.0001



View Full Table | Close Full ViewTable 3.

Average values for cover and corn grain measurements as affected by cover treatment (red clover or winter fallow) averaged across system treatments for 2006 and 2007 in a long-term field experiment at the Kellogg Biological Station in southwest Michigan.

 
Year Cover Cover biomass Cover biomass N Corn biomass Corn biomass N Corn grain yield Corn grain N
Mg ha–1 kg N ha–1 Mg ha–1 kg N ha–1 Mg ha–1 %
2006 red clover 2.21 a† 80.73 b 14.24 a 121.65 b 7.20 a 1.10 c
winter fallow 1.17 b 31.21 c 11.77 b 91.91 c 5.16 b 0.96 d
2007 red clover 2.07 a 92.64 a 13.11 a 174.48 a 7.19 a 1.53 a
winter fallow 0.76 c 20.13 c 11.20 b 126.26 b 6.39 a 1.34 b
Average values followed by the same letter are not significantly different (P < 0.05).



View Full Table | Close Full ViewTable 4.

Average values for corn grain yield measurements among conventional (CO; 2007 only), integrated fertilizer (IF), integrated compost (IC), and organic (OR) systems, averaged across cover treatments for 2006 and 2007 in a long-term field experiment at the Kellogg Biological Station in southwest Michigan.

 
Year System Cover biomass Cover biomass N Corn biomass Corn biomass N Corn grain yield Corn grain N
Mg ha–1 kg ha–1 Mg ha–1 kg N ha–1 Mg ha–1 %
2006 IF 1.40 b† 45.92 c 11.32 c 87.79 c 5.04 c 0.97 d
IC 1.86 a 60.66 b 13.87 a 114.40 b 6.71 ab 1.02 cd
OR 1.81 a 61.34 ab 13.84 a 118.11 b 6.81 ab 1.10 c
2007 CO 1.20 b 45.17 c 11.14 c 123.41 b 6.40 b 1.30 b
IF 1.22 b 50.14 c 11.16 c 126.25 b 6.43 b 1.34 b
IC 1.36 b 54.51 bc 12.79 b 170.31 a 7.07 ab 1.54 a
OR 1.88 a 75.73 a 13.53 ab 181.52 a 7.27 a 1.56 a
Average values followed by the same letter are not significantly different (P < 0.05).



View Full Table | Close Full ViewTable 5.

Sources of variation among systems (conventional, integrated fertilizer, integrated compost, and organic) and years (2006 and 2007) for the net cover biomass N and apparent red clover N credit.

 
Source of variation P > F
Net cover biomass N Apparent N credit
System 0.9407 0.6712
Year 0.0016 0.0463
System × year 0.9590 0.4708



View Full Table | Close Full ViewTable 6.

Average values for cover biomass N, corn biomass N, net cover biomass N, and apparent N credit for conventional (CO), integrated fertilizer (IF), integrated compost (IC), and organic (OR) cropping systems for 2006 and 2007 in a long-term field experiment at the Kellogg Biological Station in southwest Michigan.

 
Year System Cover Cover biomass N Corn biomass N Net cover biomass N Apparent N credit
kg N ha–1
2006 IF red clover 70.91 97.82 49.99 bc† 20.04 b
winter fallow 20.92 77.78
IC red clover 85.63 131.96 49.95 bc 35.05 ab
winter fallow 35.68 96.91
OR red clover 85.66 135.18 48.64 c 34.13 ab
winter fallow 37.02 101.05
2007 CO red clover 79.27 151.05 68.16 abc 55.27 a
winter fallow 11.11 95.78
IF red clover 86.32 150.50 72.36 abc 48.51 a
winter fallow 13.96 101.99
IC red clover 91.43 195.06 73.84 ab 49.51 a
winter fallow 17.59 145.55
OR red clover 113.58 201.35 75.70 a 39.65 ab
winter fallow 37.88 161.70
Average values followed by the same letter are not significantly different (P < 0.05).