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Managing Weeds While Transforming Marginal Land Into Perennial Forages Production

Two side-by-side fields. The left field is planted with perennial grass. The right field is bare with salty soil exposed.

Originally written with contributions by Gared Shaffer, former SDSU Extension Weeds Field Specialist.

There are currently millions acres across South Dakota impacted by saline and sodic conditions. The financial burden to produce cash crops on these marginal areas can be difficult to impossible. The goal of Every Acre Counts “is to improve the profitability, diversity, and ecological benefits of agriculture by using precision technologies to empower producers to help make informed management decisions for every acre of their operations.” One management decision is to decrease the undesirable weed vegetation on these lands and growing plant species that produce beneficial vegetation. There are options to manage marginal soils in row crop production to increase their productivity and decrease weeds. Research has shown that salt-tolerant perennial grasses are a possible way to bring land back into production. Perennial species improve the soil by keeping the ground covered (preventing evaporation) and cycling water and nutrients through the soil using deep penetrating root systems. Soil surface salts are carried downward through the soil decreasing the salt content and returning productivity for other plants not tolerant to salt.

Managing Weeds on Marginal Land 

Tillage is often preformed to manage marginal land areas, but a ‘perennial crop’ is better than any type of tillage, because the plants cycle the excess water and salts, lowering the salts in the soil profile. The ground cover could be weeds, cover crop or perennial salt tolerant plant species. Any cover on the ground surface is better than tillage for cycling nutrients and water. Once the site is dry and equipment can be used, terminate the weeds with an herbicide or clipping with a mower will help decrease weed seed production during the growing season. Salt Tolerant perennial species can be planted anytime into the annual weeds. If having weeds is undesired then a cover crop planted during the growing season can give cover for a fall planting of a perennial grass species. As a perennial grass species develops, annual weeds will decrease due to rapid growth and natural competitive nature of perennial grasses. Grasses also give opportunity to control unwanted annuals, biennials and perennial weeds through herbicide application or mowing. Having a beneficial grass growing on marginal lands gives the producer the option to have supplemental forage immediately and help bring the land back into profitable row crop production in the future. However, improper soil water use by cash crops, will require a rotation with perennial plant species to keep salts from coming back to the soil surface.