Impact of Compost and Compost Extract As Amendments on Soil, Plant Biomass, and Corn Grain Yield.

Growers who grow continuous corn conventionally without including cover crop as part of crop rotation may experience a decline in corn yield and soil fertility. Amending soil with compost and or compost extract may aid in improving soil quality and corn yield. To test that, we amended soil with either Compost (C), Extract (E), or Compost +Extract (CE) and compared to the standard grower’s practice treatment (S) with four replications in a RCB design. Three weeks before planting corn, compost was surface applied at the rate of 1 tons/acre in C and CE plot. Compost extracts were applied three times during the season. Soil samples were collected before each treatment application and analyzed for %C, %N, pH, and EC. At harvest, from each treatment per replicate, 10 whole plant samples were hand collected in 2.3 m2 (25 ft²), dried, weighed for biomass, ground and analyzed for nutrients. At the same time, corn cobs were harvested from another 2.3 m² (25 ft²) per treatment per replicate, weighed, dried, shelled, and corn grain yield was determined.

Results showed that soil %C and %N were similar in CE to those of S treatment and no significant difference among treatments. However, soil bulk density was significantly reduced from 1.45 g.cm^-3 in the S treatment to 1.35 g.cm^-3 in the CE treatment. There was no significant difference in mean dry whole plant biomass between treatments. Similarly, there was no significant difference in corn grain yield, however, corn grain yield was greater in all treatments amended with either C (11,501 kg.ha^-1; 183.37 bu.acre^-1), E (11,442 kg.ha^-1; 182.43 bu.acre^-1) or their combination CE (11,094 kg.ha^-1; 176.89 bu.acre^-1) when compared to the S treatment (10,861 kg.ha^-1; 173.16 bu.acre^-1). The harvest index (kernel per whole plant weight) was highest in the E treatment (0.57) followed by C and CE (0.55) and lowest in the S treatment (0.51). Results showed that in addition to reduction in soil bulk density, a corn grower who grows about 3000 acres annually could also gain an additional $16,500 for an increase in corn yield by 10 bushels per acre.