Cover crops, buffer strips, and precision fertilizing — how NJ farmers can be part of the solution

Published by NJ Clean Stream  |  Agricultural Runoff Series, Article 3 of 3

The path to clean water in the Delaware watershed runs through farms, not around them. The farmers of South Jersey can be genuine partners in achieving the water quality goals that downstream communities depend on. The best management practices described in this article work — and the farmers who have adopted them often report not just environmental benefits but economic benefits as well.

Cover crops: the most powerful tool for reducing nitrate leaching

Cover crops are non-cash crops planted between cash crop harvest and the following season’s planting — typically in the fall after corn, soybean, or vegetable harvest, remaining through winter and early spring. They are one of the most effective and cost-effective tools available for reducing nitrate leaching from agricultural fields into the water table.

The mechanism is straightforward: a living plant actively takes up water and nutrients through its root system. Residual nitrogen left in the soil after harvest — which would otherwise leach to the water table over fall and winter — is taken up by the cover crop instead, held in the crop’s biomass until spring, then released slowly as the cover crop decomposes. The nitrogen the cover crop scavenges from the soil profile is nitrogen that does not reach the groundwater.

Studies in mid-Atlantic Coastal Plain environments similar to South Jersey’s have documented cover crop nitrate reductions in drainage water of 30 to 90 percent, depending on species, planting date, and management. The most effective species for nitrate scavenging — cereal rye, winter wheat, oats, annual ryegrass — have extensive root systems and high nitrogen uptake capacity in the fall growing period.

Economic reality: Cover crops have direct costs of $25–$75 per acre (seed, planting, termination). These are partially offset by improved soil health, reduced erosion, potential fertilizer savings, weed suppression, and improved water infiltration. For most South Jersey farmers, the net economic impact is modest — slight cost in some situations, modest benefit in others. The environmental benefit accrues primarily to downstream communities, not the farmer bearing the management burden. This is the classic case for public cost-share support, and New Jersey’s programs have demonstrated that expanding cost-share funding significantly increases adoption rates.

Vegetated buffer strips: intercepting runoff before it reaches the stream

A vegetated riparian buffer strip is a strip of perennial vegetation — grasses, shrubs, trees, or combinations — established along streams, ditches, and waterways adjacent to agricultural land. When surface runoff reaches the buffer, velocity slows due to vegetation resistance. Suspended sediment settles out and is deposited. Dissolved nutrients are captured with sediment. Water infiltrating through the buffer’s soil encounters plant roots and microbial communities that take up or transform dissolved nitrogen.

Studies have documented nitrogen removal rates of 30 to 90 percent and sediment removal rates of 50 to 90 percent in well-established buffers of adequate width — typically 25 to 100 feet depending on slope and loading rates. Buffer strips also stabilize stream banks, provide shade that keeps streams cool for fish, provide wildlife habitat, and can be enrolled in conservation easement programs that provide additional payments to landowners.

The enrollment challenge: Buffer strips require taking cropland out of production — a real opportunity cost for farmers operating on thin margins. Federal CRP payments partially compensate for this cost, but payment rates may not fully reflect the value of the land in production on the most productive South Jersey soils. Achieving high adoption rates on the most important stream corridors requires either substantially enhanced payment rates or regulatory requirements making buffer establishment obligatory for farms above a specified nutrient contribution level.

Precision nutrient management: applying only what the crop needs

Precision nutrient management applies fertilizers and manures at rates, timings, and placements that match the crop’s actual nutrient needs — determined by soil testing, yield history, and crop modeling — rather than based on general recommendations or traditional practices. The goal is to provide the nutrients the crop needs for maximum economic yield while minimizing the residual nutrients available for leaching or runoff.

In South Jersey’s variable Coastal Plain soils — where organic matter, texture, and drainage vary significantly across even small fields — precision management increasingly uses variable-rate application technology, allowing fertilizer spreaders to vary rates across a field based on GPS-linked maps of soil properties and yield history.

The economic case is strong: Fertilizer is expensive, and applying more than the crop needs wastes money. Studies have found that many South Jersey farms apply nitrogen at rates that exceed crop demand — either from conservative application practices or inadequate accounting for nitrogen from organic sources. Reducing over-application saves fertilizer costs while reducing leaching losses. NJ’s Nutrient Management Program requires nutrient management plans for farms above specified thresholds, providing a framework for precision management — but implementation quality varies with available resources and technical capacity.

Constructed wetlands and controlled drainage: advanced tools

Constructed wetlands are engineered wetland systems built to intercept and treat nutrient-laden drainage water before it reaches streams. They achieve 50–90 percent nitrate removal through plant uptake, sediment deposition, and denitrification — the microbial process that converts nitrate to nitrogen gas. Capital costs are significant ($1,000–$5,000 per acre-foot of wetland volume), but cost-share funding through NRCS’s Wetland Reserve Easement program can offset construction costs and provide long-term rental payments for the land in wetland use.

Controlled drainage uses adjustable water control structures in subsurface tile drainage systems to hold the water table higher during non-cropping periods, reducing drainage flows that carry nitrate to surface water. Studies in the mid-Atlantic Coastal Plain have documented nitrate load reductions of 30–50 percent with well-implemented controlled drainage systems.

The farmer perspective: what makes conservation work on the ground

The most effective conservation programs share several characteristics. They provide meaningful financial support — not token payments, but cost-share rates that genuinely reflect the farmer’s out-of-pocket costs plus a modest incentive that makes participation economically rational. They involve trusted advisors — the NRCS field office agronomist who has worked with the same farming community for years, the Rutgers Cooperative Extension agricultural agent who understands local soil conditions. They respect farmers’ expertise and autonomy, treating them as professionals who understand their land rather than as problems to be managed.

The most common reasons for non-participation are oversubscription — wanting to participate but being turned away because the program is out of funding — and administrative burden — paperwork and compliance requirements imposed in excess of what is necessary for environmental effectiveness. Both are policy problems that can be addressed: adequate funding eliminates oversubscription, and streamlined administration reduces burden without sacrificing accountability.

A policy framework that works: the final message of this series

Clean water in the Delaware watershed is achievable — not easily, not quickly, and not without significant investment and some degree of regulatory accountability — but genuinely achievable with the right combination of mandatory baseline requirements, robust financial incentives, and a culture of partnership.

  • The mandatory elements — nutrient management planning with verification, TMDL-based load reduction targets, regulatory backstops for farms consistently exceeding acceptable loading — provide the accountability framework that voluntary programs alone cannot deliver.
  • The incentive elements — well-funded cost-share programs, technical assistance, conservation easement payments — provide the support that makes conservation practices economically viable for farms on thin margins.
  • The partnership elements — farmer engagement in program design, trusted advisor relationships, recognition of farming’s positive contributions to the landscape — create the culture of shared responsibility that makes long-term progress possible.

The people who drink from the Delaware River and its tributaries deserve clean water. The farmers who work the land of the watershed deserve fair treatment, adequate support, and recognition of their role in the ecosystem. These interests are not incompatible. Making them complementary is the work of good water policy — and it is work that NJ Clean Stream is committed to pursuing.

This is Article 3 of 3 — and the final article in NJ Clean Stream’s nine-series water quality content library. Article 1 explains the scale of agricultural nutrient loading in the Delaware watershed. Article 2 examines the regulatory framework that exempts agriculture from Clean Water Act requirements that govern every other pollution source.