Date of Graduation

2014

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Horticulture

Committee Chair

Eugenia M Pena-Yewtukhiw

Committee Co-Chair

Alan J Sexstone

Committee Member

Nicole L Waterland

Abstract

In the past few decades, organic productions systems have become increasingly popular due to rising environmental awareness. Much research has been done on crop rotations and fertilization in conventional agricultural systems, but because organic management practices are often different from those in conventional systems, much is unknown about the effect of organic management practices on soil quality. Composted manure and a temporary grass component within an organic crop rotation may be capable of improving soil quality, and may be particularly important in the absence of synthetic chemical inputs. The objective of this research was to evaluate soil quality changes in two different rotations: with and without grass and at two rates of manure application. Variables measured were bulk density (BD), wet/dry aggregate stability (WA/DA Geometric Mean Diameter), bioavailable nutrients (Soil Organic Matter, N, P, K, Ca, Mg, Zn, TotN), and biomass. Additionally, the transition was examined from crop into temporary grass component, and from grass component back into crops. This research was conducted on an existing crop rotation experiment at the WVU Organic Farm in Morgantown, WV.;Two rotations were studied: of four and seven year durations, with the same crop sequence (corn, soy, wheat, kale), and three years of orchard-grass/red clover added to the 7-year rotation. Two bi-annual manure rates: unmanured (U):0 and manured (M):22.5Mg/ha) were applied to corn and wheat plots. Analysis of variance (ANOVA) was performed on the data. Measurements were taken in corn (C) and kale (K) plots, to represent the beginning and the end of the cropping cycle, and on first (Orchardgrass 5, or O5) and last (Orchardgrass 7, or O7) years of grass component. Two years of data (2013 and 2014) show very similar results for both experiments. Results of Experiment 1 show that, within rotation, manure application nearly always significantly improved soil physical and chemical properties (e.g. for 2013, Bulk density (BD) 4-yr Manured (M): 1.09Mg/m3, 4-yr Unmanured (U): 1.22Mg/m3, 7-yr M: 1.15Mg/m3, 7-yr U: 1.24Mg/m3; Soil Organic Matter 4-yr M: 3.9%, 4-yr U: 2.7%, 7-yr M: 4.9%, 7-yr U: 3.2%; pH 4-yr M: 5.8, 4-yr U: 5.0, 7-yr M: 5.9, 7-yr U: 5.2; Phosphorus 4-yr M: 96.7mg/kg, 4-yr U: 19.7mg/kg, 7-yr M: 70.8mg/kg, 7-yr U: 26.2mg/kg; Total Nitrogen 4-yr M: 2.7%, 4-yr U: 1.7%, 7-yr M: 2.9%, 7-yr U: 2.2%). Corn and cowpea biomass were also higher in manured plots than in unmanured plots [Corn Biomass 4-yr M: 326g, 4-yr U: 248g, 7-yr M: 436g, 7-yr U: 253g; Cowpea Biomass 4-yr M: 8.63 Mg/ha, 4-yr U: 5.69 Mg/ha, 7-yr M: 9.47 Mg/ha, 7-yr U: 4.25 Mg/ha]. "Between-rotation" results for manure application were very similar to those found within rotation.;A significant effect of crop was observed within rotation. Soil quality was often found to be higher in corn plots than in kale plots (e.g. DA-GMD 7-yr C: 5.1 mm, 7-yr K: 4.3 mm; WA-GMD 7-yr C: 4.9 mm, 7-yr K: 2.6 mm; SOM 4-yr C: 3.5%, 4-yr K: 3.1%; 7-yr C: 3.7%, 7-yr K: 3.5%; pH 7-yr C: 5.6, 7-yr K: 5.4; P 4-yr C: 86.9 mg/kg, 4-yr K: 29.6 mg/kg, 7-yr C: 72.9 mg/kg, 7-yr K: 24.5 mg/kg). This may be due to the fact that composted manure is added directly to corn plots, and not to kale plots. Interactions were observed between manure and crop.;The 7-yr rotation significantly improved bulk density (BD 4yr C: 1.7 Mg/m3, 7yr C: 1.3 Mg/m3), DA-GMD (4yr C: 3.9mm, 7yr C: 5.1mm), WA-GMD (4yr C: 3.2mm, 7yr C: 4.9mm) and soil organic matter (SOM 4yr C: 3.1%, 7yr C: 3.5%), and appeared to have a protective effect of SOM. Regardless of crop, Total N was also higher in the 7-yr rotation (C: 2.8%, K: 2.2%) than in the 4-yr rotation (C: 2.3%, K: 2.0%). The 7-yr rotation, however, did not always improve aggregate stability or plant available nutrients (WA-GMD 4yr K: 3.0mm, 7yr K: 2.7mm; P, 7-yr C: 72.9mg/kg, 4-yr C: 86.9mg/kg, and 7-yr K: 24.5mg/kg, and 4-yr K: 29.6mg/kg). Corn and cowpea biomass were highest in plots receiving the combination of the manure treatment and the 7-yr rotation treatment (e.g. Corn Biomass 4-yr M: 326g, 4-yr U: 248g, 7-yr M: 436g, 7-yr U: 253g). An interaction was found between manure addition and rotation.;In 2013, results of Experiment 2 show the effect of the transition into and out of the temporary grass component. The transition from crops into grass showed an improvement in soil quality (e.g. BD K: 1.14, O5: 1.19; DA-GMD K: 4.4mm, O5: 6.4mm; Calcium K: 1728mg/kg, O5: 2015mg/kg). This improvement reversed during the transition out of the temporary grass component (e.g. BD O7: 1.24, C: 1.13; DA-GMD K: 6.1mm, O5: 5.1mm; Calcium O7: 2135mg/kg, C: 1938mg/kg). These changes reflect a pause in tillage and the effect of the grass component, and subsequent resume in tillage.;This research supports the use of manure application and the use of a temporary grass component in an organic rotation to improve soil physical quality. The research also increases the understanding of the effect of a grass component within organic rotations on soil quality, and would benefit from additional organic long-term rotational research.

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