Effect of nutrient management planning on crop yield, nitrate leaching and sediment loading in Thomas Brook watershed

Impacts of no-tillage management on nitrate loss from corn, soybean and wheat cultivation: A meta-analysis

Although no-till (NT) has been promoted as an alternative land management practice to conventional tillage (CT), its impact on water quality, especially nitrate (NO3-) loss remain controversial. We conducted a meta-analysis to compare NO3- concentration and load in NT and CT systems via two major transport pathways: runoff and leaching. Rainfall variability, aridity, soil texture, tillage duration, crop species, and fertilizer type were used as co-varying factors. In comparison to CT, NT resulted in an overall increase of runoff NO3- concentration, but similar runoff NO3- load. In contrast, leachate NO3- load was greater under NT than under CT, although leachate NO3- concentration was similar under both tillage practices, indicating that the effect of NT on NO3- load was largely determined by changes in water flux. Some deviations from these overall trends, however, were recorded with different co-varying variables. In comparison to CT, NT, for example, generated lower leachate NO3- concentration and similar (instead of elevated) NO3- leachate load from soybean fields (no N fertilizer applied). These results suggest NT needs to be complemented with other practices (e.g., cover crops, reduced N rate, split N application) in order to improve soil N retention and water quality benefits.

Meta-Analysis of Phosphorus Loss from No-Till Soils

Agriculture is a significant contributor to phosphorus (P) enrichment in aquatic ecosystems. No-till (NT) farming has been proposed as an alternative approach to conventional tillage (CT) in reducing soil P export, but published data have shown contrasting impacts, likely due to the interacting effects of different physical (climate region, rainfall variability, transport pathway, slope gradient) and management variables (NT duration, crop species). We conducted a meta-analysis to understand the extent to which each of these variables controls the concentration and load of different P fractions (dissolved P, particulate P) in agricultural runoff and leaching. In comparison with CT, particulate P loss was significantly lower with NT adoption (45 and 55% reduction in concentration and load, respectively), but an increase in dissolved P loss was observed. The extent of the reduction or increase, however, varied with different physical and management variables. In comparison with CT, for example, NT was not effective in reducing particulate P concentration during wet years and particulate P load on steep slopes (4-9%). Total P concentration was also similar with CT at sites under prolonged NT duration (∼10 yr) and at NT fields planted with soybean [ (L.) Merr.]. Our results underscore the need to consider the covarying physical and management factors when assessing the potential of NT farming in controlling P loss in the environment. The limited impact of NT on dissolved P loss remains a serious impediment toward harnessing the water quality benefits of this management practice.