DRAINAGE PROJECT ENTERS A NEW PHASE

Increased awareness of the impact of nutrient loading from agricultural activities has driven public and producer interest alike in adopting practices such as cover cropping (CC) and no tillage (NT) corn production. While considerable strides have been made in adapting these practices to northern climates with short growing seasons, harsh winters, and unpredictable weather in the fall harvest and spring planting windows, there has been much less focus as to whether the intended environmental benefits are being achieved.

Research has demonstrated that the agronomic benefits of NT+CC in combination is greater than the sum of the benefits of either practice in isolation. Therefore, NT is rarely implemented without the accompanying usage of CC.

Much of the cropland in the Lake Champlain Basin of New York and Vermont has a high potential for surface runoff due to the topography and an abundance of poorly drained soils. The limited soil disturbance and increased residue cover with NT management can result in significant reductions of sediment and particulate phosphorus (P) in surface runoff. Conversely, the improved soil structure in NT fields can result in elevated subsurface losses of P through preferential flow pathways in fields with systematic tile drainage, especially when manure is applied and remains on the soil surface. Cover cropping is often paired with NT production as the continuous vegetative cover and root system enhances the development of soil structure. The living CC in the fall and spring (when planting winter hardy varieties such as cereal rye) helps remove plant available P and nitrogen (N) that could otherwise be lost in runoff. Tile drainage has and continues to be widely adopted in the region, and research has demonstrated the potential for NT+CC systems to contribute a significant proportion of annual P and N loads in certain circumstances. Understanding how the conversion to NT+CC impacts field hydrology (surface vs tile drainage), nutrient dynamics, and the potential tradeoffs that may occur with conversion to NT+CC in tiled fields is critical to developing sound recommendations for producers.

Despite the possible benefits to the producer, there are also challenges related to implementing NT+CC in corn fields. Short growing seasons, allelopathic effects on the subsequent corn crop, water and nutrient competition between the CC and corn during the early growth stages, can all impact the quality and yield of the corn crop. Although cereal rye is a winter hardy crop that can be planted as late as October 10 in the region, it’s not unusual for CC to be planted well into October. Understanding the degree to which a well-established CC compared to a low biomass CC stand will impact water quality metrics is important for real-world assessment as conditions are rarely ideal.

The same surface runoff monitoring location at the corner of the previously untiled field is pictured at different times of the year. Notice that despite the same approximate rate of drainage, the potential for increased erosion when there isn’t a growing crop to anchor the soil in place and protect the soil from raindrops with its leafy canopy.

From 2018-2022, two fields in Keeseville, NY were monitored for surface and tile drainage water quality. While surface drainage was monitored and sampled from both fields, only one of the fields was tile drained. During this 5-yr period, it was clear that tile drainage had a substantial impact on the water balance for each field; total drainage was 46% greater in the tiled versus untiled field, but the primary runoff pathways differed with the vast majority of drainage from the tiled field occurring through the subsurface. This increased soil drainage capacity also resulted in 244% greater N losses from the tiled field, but no meaningful differences were observed for P.

As we enter the new phase of the project, the untiled field has now been tiled (summer 2023) and sampling began in December 2023. Currently both fields are being managed with conservation tillage and no winter cover crop to develop a new baseline comparison of their surface and tile drainage water quality. The NT+CC management will begin in one of the fields in 2026. This study will provide an opportunity to collect data that will enhance the experimental rigor of the previous study at this site (impacts of tiling), allowing for more robust and scientifically defensible conclusions to be drawn, while simultaneously generating data for the investigation of the environmental and agronomic benefits of NT+CC corn silage production and whether this system can help mitigate the additional N losses that occur when fields are tiled.

— Laura Klaiber

klaiber@whminer.com