Editing Crop rotation (section)

=== Soil organic matter ===

The use of different species in rotation allows for increased soil organic matter (SOM), greater soil structure, and improvement of the chemical and biological soil environment for crops. With more SOM, water infiltration and retention improves, providing increased drought tolerance and decreased erosion.

Soil organic matter is a mix of decaying material from biomass with active [[microorganism]]s. Crop rotation, by nature, increases exposure to biomass from sod, green manure, and various other plant debris. The reduced need for intensive [[tillage]] under crop rotation allows biomass aggregation to lead to greater nutrient retention and utilization, decreasing the need for added nutrients.<ref name=baldwinCEFS/> With tillage, disruption and oxidation of soil creates a less conducive environment for diversity and proliferation of microorganisms in the soil. These microorganisms are what make nutrients available to plants. So, where "active" soil organic matter is a key to productive soil, soil with low microbial activity provides significantly fewer nutrients to plants; this is true even though the quantity of biomass left in the soil may be the same.

Soil microorganisms also decrease [[pathogen]] and [[pest (agriculture)|pest]] activity through competition. In addition, plants produce root exudates and other chemicals which manipulate their soil environment as well as their weed environment. Thus rotation allows increased yields from nutrient availability but also alleviation of [[allelopathy]] and competitive weed environments.<ref name="One Earth 2020 pp. 284–293">{{cite journal |title=Long-Term Evidence Shows that Crop-Rotation Diversification Increases Agricultural Resilience to Adverse Growing Conditions in North America |journal=One Earth |volume=2 |issue=3 |date=20 March 2020 |issn=2590-3322 |doi=10.1016/j.oneear.2020.02.007 |pages=284–293 |last1=Bowles |first1=Timothy M. |last2=Mooshammer |first2=Maria |last3=Socolar |first3=Yvonne |last4=Calderón |first4=Francisco |last5=Cavigelli |first5=Michel A. |last6=Culman |first6=Steve W. |last7=Deen |first7=William |last8=Drury |first8=Craig F. |last9=Garcia y Garcia |first9=Axel |last10=Gaudin |first10=Amélie C.M. |last11=Harkcom |first11=W. Scott |last12=Lehman |first12=R. Michael |last13=Osborne |first13=Shannon L. |last14=Robertson |first14=G. Philip |last15=Salerno |first15=Jonathan |last16=Schmer |first16=Marty R. |last17=Strock |first17=Jeffrey |last18=Grandy |first18=A. Stuart |display-authors=5 |bibcode=2020OEart...2..284B |s2cid=212745944 |doi-access=free |hdl=10214/21229 |hdl-access=free }}</ref>