ABSTRACT
Reduced tillage management conservation practices (No-till and Reduced-till) are widely adopted in agriculture; however, understanding their overall effectiveness for water quality protection is challenging. A meta-analysis was conducted to understand and quantify the effectiveness of residue and tillage management on runoff, sediment, and nutrient losses from agricultural fields. Annual runoff and the associated sediment, and nutrient (nitrogen and phosphorus) loads were compiled from 60 peer reviewed research articles published across the United States and Canada. A total of 1575 site-years of data were categorized into tillage (<30% surface cover), no-tillage (<30% surface cover), tillage with residue (>30% surface cover), no-tillage with residue (>30% surface cover), and pasture management. No-tillage, no-tillage-residue, and tillage-residue managements were evaluated for their effectiveness in reducing runoff, nutrients, and sediment loads compared to tillage. Synthesized and surveyed corn yield data were used to evaluate the economic cost effectiveness of no-tillage-residue management with respect to tillage. Across the site years (1968-2019) studied, median runoff depth for no-tillage and no-tillage-residue were 84% and 70% greater than tillage and tillage-residue management, respectively. No-tillage-residue management had up to 86% less sediment losses than tillage systems, on average, for both >30% and <30% surface cover. No-tillage-residue management was most effective, with a positive performance effectiveness of 65% to 90% in controlling sediments, particulate, and total nutrient losses in runoff compared to tillage. Cost effectiveness analysis revealed the benefits of no-tillage-residue management in reducing nutrient loads and increasing net-farm revenue by avoiding tillage operational costs. Except for dissolved phosphorus, no-tillage-residue management cost effectiveness for sediments and nutrient loads ranged from negative $6 to negative $102 per every Mg or kg of load reduction, indicating it had both economic and environmental benefits compared to tillage management. Overall, these results indicate that over the long-term, no-tillage and tillage, combined with greater than 30% residue cover, can effectively reduce sediment and nutrient losses. This work highlights the importance of crop residues on the soil surface to reduce runoff losses, even in no-tillage systems.
ABSTRACT
In cold regions, nutrient losses from dairy agroecosystems are a longstanding and recurring problem, especially when manure is applied during winter over snow-covered frozen soils. This study evaluated two tillage (fall chisel tillage [CT] and no-tillage [NT]) and three manure-type management treatments (unmanured control, liquid manure [<5% solids], and solid manure [>20% solids]). The liquid and solid manure used in this study were from the same animal species (Bos taurus) and facility. The six management treatments were field tested in south-central Wisconsin during the winters (November-April) of 2017-2018 and 2018-2019 with a complete factorial design. Seasonal runoff losses were significantly lower from fall CT compared with NT during both seasons. Manure applications (both liquid and solid) on top of snow significantly increased most of the nutrients (NH4 + , dissolved reactive phosphorus, total Kjeldahl nitrogen, and total phosphorus) in runoff compared with unmanured control. Irrespective of tillage and multiple runoff events, solid manure was present on the surface for longer periods, potentially releasing nutrients each time it interacted with runoff. In contrast, liquid manure infiltrated the snowpack and was partly lost with snowmelt and infiltrated soil depending upon soil frost and surface conditions. Overall, results indicate that wintertime manure applications over snow-covered frozen soils pose a risk of nutrient loss irrespective of tillage and manure type, but in unavoidable situations, prioritizing tillage × manure type combination can help reduce losses.