USDA ARS: CQSTER model can evaluate soil quality

By Anna Austin | November 03, 2008
Web exclusive posted Nov. 25, 2008 at 12:46 p.m. CST

The development of soil management practices to maintain adequate soil organic matter (SOM) is essential for making prudent decisions regarding land use for food, fiber, feed and bioenergy, according to an article by the USDA-Agricultural Research Services which was recently published in the Soil Science Society of American Journal.

The report details methods of measuring soil quality using the carbon sequestration (CQSTER) model, and predicts long-term soil organic matter and soil organic carbon changes caused by an array of practices including crop residue removal.

The CQSTER model is described in the report as a tool used to relate organic residue additions, crop management, and soil tillage to SOM accretion or loss. "Given the high correlation of simulated and observed SOM changes, CQESTR can be used as a reliable tool to predict SOM changes from management practices and offers the potential for estimating soil carbon storage required for carbon credits," the article stated. "It can also be an important tool to estimate the impacts of crop residue removal for bioenergy production on SOM level and soil production capacity."

ARS scientists selected four previously conducted long-term experiments with several management systems to examine the ability of the CQSTER to simulate the long-term effects of practices such as crop rotation, organic amendments and tillage practices. Two of the experiments were 100-year studies done in Champaign, Ill., and Columbia, Mo., and the other two were 20-year studies done in Lincoln and Sidney, Neb.

The CQSTER model successfully simulated the detrimental effect of 50 or more years of crop residue removal on SOM dynamics, according to the report. "Management practices that increase biomass, limit inversion tillage, and return root and shoot biomass to the soil annually promote C accretion," it stated. "The CQESTR model can be used to examine the expected effect of planned or proposed changes in agricultural management practices on soil C contents at the field scale."

The scientists also found that the use of the CQESTR model allows evaluation of management options so that sustainability can be considered along with soil productivity. "More studies are needed to evaluate the CQESTR model's performance in predicting the amount of crop residue required to maintain the SOM concentration in different soils under a wide range of management and climatic conditions," the article concluded.

The report is available on the Soil Science Society of American Journal Web site at no charge until Dec. 20.