Tillage and reduced-input rotations affect runoff from agricultural fields

Seed Daily via SPX: No-till management practices can reduce soil erosion, but evidence suggests they can also lead to increased runoff of dissolved phosphorus from soil surfaces. Meanwhile, farmers looking to avoid herbicides often have to combat weeds with tillage, which causes erosion. With all of the tradeoffs of different management systems, which one should growers use? To answer that question, researchers from the USDA Agricultural Research Service compared nutrient and sediment loss from no-till, conventional tillage, and reduced-input rotation watersheds in a study published online in Soil Science Society of America Journal.

By keeping a protective layer of plant matter on the soil surface, no-till practices reduce the loss of soil and phosphorus (P) attached to soil particles. But no-till requires herbicides to control weeds, and even after adoption of the practice by many farmers, harmful algal blooms were still occurring in surface waters. It looked as if no-till, while decreasing particulate P loss, was leading to increased runoff of dissolved P.

"Normally when you apply P-containing fertilizers, you would incorporate them into the soil," says Martin Shipitalo, lead author of the study. "With no-till, you're just broadcasting it on the soil surface, leading to high P concentrations at the surface. Even if you get less particulate loss, runoff will pick up that dissolved P that's highly concentrated at the soil surface."

Shipitalo and his team decided to look at data from a 16-year experiment to compare soil and nutrient runoff in watersheds managed in three different ways - no-till, conventional tillage (chisel-till), and reduced-input rotations. "The idea with the reduced-input rotation was to have a conservation practice that worked for farmers who do not want to use herbicides or large amounts of mineral fertilizers," explains Shipitalo.

In the current study, researchers provided most of the nutrients to crops in the reduced-input watersheds by planting red clover and spreading manure instead of fertilizers. They minimized the amount of bare soils and used just a shallow disking instead of total inversion tillage to leave some crop residue on the soil surface. While herbicides were used in the experiment, they aren't necessary because the light tilling and in-row cultivation that was done kept weeds under control.

"Reduced-input rotations strike a medium between conventional tillage and no-till," says Shipitalo. "And they could easily be adapted to be organic rotations."...

Ferdynand Rusczcyc's 1898 painting, "The Soil"

Reduced tillage doesn't mean reduced cotton yields under drip irrigation

Terra Daily via SPX: Loss of production may be one concern cotton producers have on the Rolling Plains when considering switching to reduced- or no-tillage systems, said Dr. Paul DeLaune, Texas AgriLife Research environmental soil scientist in Vernon. Not only will cotton growers not lose production with subsurface drip irrigation, their economics will improve, according to DeLaune's latest research article that will appear in the July-August issue of Agronomy Journal.

DeLaune's study on cotton production as affected by irrigation level and transitioning tillage systems was designed to identify water management strategies that conserve and protect water resources within semiarid environments.

"We found that tillage has no impact on yields, the net returns are greater and, because we can deficit irrigate, we can save energy and water," he said.

The three-year study included five irrigation regimes, from 0 percent to 133 percent of evapotranspiration replacement, and evaluated four tillage systems - conventional till, reduced till, no-till and no-till with a terminated cover crop, he said. Treatments were replicated three times in a randomized complete block design.

The results showed lint yields were not affected by tillage or the interaction of tillage and evapotranspiration replacement, DeLaune said. The greatest lint yields and net returns were achieved at 100 percent evapotranspiration replacement. Optimum lint yields and net returns were achieved at 104.5 percent evapotranspiration and 102 percent evapotranspiration, respectively...

A cotton field in West Texas, shot by Calsidyrose, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license