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Crop rotation is a commonly used management practice in the central U.S. whereby different agricultural crops are grown on a farm field in successive years to help maintain the productive capacity of the soil. Understanding hydrologic responses to crop rotation is critical for developing appropriate crop rotation strategies for sustainable water resources management. These responses are not well understood due to limited availability of multi-year, crop-specific land use-land cover data. The study focuses on the Smoky Hill River watershed in west-central Kansas, a typical agro-ecosystem watershed in the Central Great Plains of the U.S. A multi-year land use dataset developed for the state of Kansas was used to identify 3-year crop rotation patterns in the watershed for three different periods (2006–08, 2008–10, 2010–12). Out of 276 unique rotations, 21 rotations were found to be dominant, with rotation patterns of grain sorghum-fallow-winter wheat (G-F-W), winter wheat-winter wheat-fallow (W-W-F), and continuous winter wheat (W-W-W) occupying more than 81% of the cropland in each rotation period. From 2006 to 2012, the coverage of grain sorghum increased by 26% and corn by 305%, while winter wheat decreased by 20%. Three 11-year simulation scenarios based on three 3-year crop rotation patterns were implemented in the SWAT model and separately calibrated for streamflow at two gauge sites. The SWAT model produced good calibration statistics for the periods corresponding to the applied crop rotations, while the statistics tended to decrease for other periods, with Nash-Sutcliffe Efficiency coefficient becoming unsatisfactory for periods of six to eight years outside of the calibration period. Applying a different number of dominant crop rotations to the SWAT model, it was found that the number can be reduced down to the five most dominant without significant loss in model performance. While the optimum number of crop rotations must be evaluated for each agricultural watershed, this finding provides valuable information for watershed model development and calibration, which can help to avoid issues of over-parameterization and equifinality. [ABSTRACT FROM AUTHOR]

Crop rotations (the practice of growing crops on the same land in sequential seasons) reside at the core of agronomic management as they can influence key ecosystem services such as crop yields, carbon and nutrient cycling, soil erosion, water quality, pest and disease control. Despite the availability of the Cropland Data Layer (CDL) which provides remotely sensed data on crop type in the US on an annual basis, crop rotation patterns remain poorly mapped due to the lack of tools that allow for consistent and efficient analysis of multi-year CDLs. This study presents the Representative Crop Rotations Using Edit Distance (RECRUIT) algorithm, implemented as a Python software package, to select representative crop rotations by combining and analyzing multi-year CDLs. Using CDLs from 2010 to 2012 for 5 states in the US Midwest, we demonstrate the performance and parameter sensitivity of RECRUIT in selecting representative crop rotations that preserve crop area and capture land-use changes. Selecting only 82 representative crop rotations accounted for over 90% of the spatio-temporal variability of the more than 13,000 rotations obtained from combining the multi-year CDLs. Furthermore, the accuracy of the crop rotation product compared favorably with total state-wide planted crop area available from agricultural census data. The RECRUIT derived crop rotation product was used to detect land-use conversion from grassland to crop cultivation in a wetland dominated part of the US Midwest. Monoculture corn and monoculture soybean cropping were found to comprise the dominant land-use on the newly cultivated lands. [ABSTRACT FROM AUTHOR]

Cropping systems in the Midwest USA are evolving as farmers seek labor-efficient designs to capture and use available light and precipitation. Heavy reliance on fossil fuels and other energy-intensive production inputs coupled with uncertain markets for commodities have encouraged the search for greater energy efficiency as well as alternative crops, markets, and production systems. Agroecology has emerged as an innovative and integrative approach to evaluating systems more suited to the often harsh and unpredictable environment, using native prairie structure and function as one guide to design of future systems. A more specific approach, Natural Systems Agriculture, is being explored as a new paradigm to saving soil while producing the crop and animal output needed for a growing global population. Whole-farm and landscape- level design and planning will become more important as society recognizes and values multifunctional rural landscapes. [ABSTRACT FROM PUBLISHER]

Nitrification potential is the maximum capacity of a soil’s population of nitrifying bacteria to transform NH4+-N to NO3−-N. Time of season and the effect of several management practices on nitrification potentials were measured via an amended slurry method, shaken for 24 h at 25 °C. Management strategies that reduce potential nitrification rates without limiting plant N uptake may increase the ratio of plant biomass to plant N content (PB:N), the aboveground net primary production (ANPP) per unit of N in ANPP, and decrease the amount of NO3− available for leaching, and/or conversion to N2O. Sites were located in Hickory Corners, MI, USA, on Haplic Luvisols. Management practices included: substitution of compost for N fertilizer, use of a rotation in place of continuous maize and the addition of cover crops. A previously tilled, successional grassland was used as a contrast to agricultural managements. Where N fertilizer was applied, nitrification potential increased in late May and again in late August–October. The seasonal pattern was similar but less pronounced where compost was applied. Nitrification rates were 4.2 times greater than that of the successional site when N fertilizer was applied. Use of N fertilizer increased nitrification potentials 1.5 times above treatments where compost was applied during 1998 and 1999 in the 6th and 7th years of the rotation. In some instances, nitrification potentials could be correlated with in situ NO3−-N measurements. Average PB:Ns in the fertilizer management were greater or equivalent to the successional grassland site. Compost increased PB:N above that of N fertilizer. Utilization of compost decreased nitrification potentials, maintained yields, and increased PB:N. The crop N content was lower when compost was applied. Thus, grain and stover quality may be lowered and need to be monitored. [Copyright &y& Elsevier]

Many lessons in long-term cropping systems experiments are learned from practical experience. I have conducted large-scale, long-term, multidisciplinary dryland and irrigated cropping systems experiments with numerous colleagues at university and government research stations and in farmers' fields in the USA and in developing countries for 25 years. Several practical lessons learned through the years are outlined in this short commentary. While some of these lessons learned may be intrinsically obvious, results of many cropping systems experiments have not been published in scientific journals due to fatal flaws in experimental design, improper transitioning between phases of the experiment and many other reasons. Ongoing active support by stakeholders is critical to maintain funding for long-term cropping systems studies. Problems and unexpected challenges will occur, but scientists can often parlay these into opportunities for discovery and testing of new hypotheses. Better understanding and advancement of stable, profitable and sustainable cropping systems will be critical for feeding the world's projected 10 billion people by the mid-21st century. [ABSTRACT FROM AUTHOR]