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Water: Is there a Problem with Too Much or Too Little? (05/06/21)

For North Dakota and Northwestern Minnesota, the above average precipitation pattern that started in 1993 resulted in unproductive areas along headlands and road-side or in-field ditches.

For North Dakota and Northwestern Minnesota, the above average precipitation pattern that started in 1993 resulted in unproductive areas along headlands and road-side or in-field ditches. However, recent dry weather is not helping these issues either (Figure 1, next page). We need more rain in sufficient quantities to force excess salts deeper into the soil to remediate salinity and to dissolve soil amendments such as gypsum to remediate sodicity.

Fig 1 PLSC

Most unproductive areas have moderate to high levels of water soluble salts (measured by analyzing electrical conductivity). Apart from salt issues, these areas either have high levels of sodicity (measured by analyzing sodium adsorption ratio) that causes breakdown of soil aggregates or high magnesium levels compared to calcium causing excess swelling of soils. These issues affect plants and soils resulting in unproductive areas and net loss of revenue.

Water is essential for all living beings including plants and soils, however, too much or too little water creates challenges. The wet cycle resulted in shallow groundwater depths, saturated soils and brought excess water-soluble salts and sodium (Na+) causing sodicity in topsoil. Whereas, dry weather increases evaporation, which results in greater wicking of groundwater, salts and sodium leaving deposits on the soil surface. Since 2017, the weather pattern started getting drier, excluding the wet fall of 2019, and currently we have drought conditions. We did not feel it in 2017 as the 2016-fall was very wet. In 2020, again we had carryover groundwater from the fall rains in 2019. However, not only was last fall dry but so far this spring has been dry as well. Dry weather is the reason saline and sodic areas are very prominent, widespread and increasing during the last two-years compared to the recent past. These areas keep growing and reduce productivity of once fertile soils. In addition, lack of plant growth increases erosion as topsoil blow away. It is dollars directly out of producer’s pocket when the precious fertile topsoil blows away.

Planting Suitable Salt-tolerant Plants

It is not in our control how much rain we will get and when, however, we can establish salt-tolerant annual crops or perennial grasses to reduce evaporation and wicking up of groundwater, salts and sodium into topsoil. Planting cash crops such as wheat, canola, corn or soybean on these saline-sodic areas will likely result in poor stands. According to the NDSU projected 2021 crop budgets for NE North Dakota, the average cost of seed, fertilizer and one third fuel and lubrication to plant one acre of spring wheat is $108.46. For canola, it is $147.61 per acre for the same inputs, whereas, for corn and soybeans the input cost is $176.12 and $82.16 per acre respectively. However, when soil saturated paste electrical conductivity or EC is close to 4.0 dS/m and sodium adsorption ratio or SAR is around 7.0, these crops generally do not do well and planting salt-tolerant crops such as barley and oats may produce better results. As per a research trial conducted at the NDSU Langdon Research Extension Center in 2020, barley and oats produced high yields when 0-6 inch depth soil EC was 3.99 dS/m with a SAR of 7.12. However, at a EC of 7.80 dS/m and a SAR of 18.13 for the same soil depth, there were 75 and 65 percent yield reductions across the board for barley and oat varieties respectively (Figure 2 and 3).

Fig 2 3 PLSC

However, once soil EC is 5.50 or more and SAR is 10.00 or more, it is best to plant perennial salt-tolerant grasses. Once established, they can be hayed or grazed to generate some profit from these currently unproductive areas. Salt-tolerant perennial covers will also minimize wicking up of groundwater, salts and sodium and will minimize blowing of topsoil. These grasses will grow at EC levels ranging from 14.0 to 26.0 dS/m. Strips could be 30 to 50 feet wide along the headlands, road-side or in-field ditches (Figure 4). It takes about one-year for these grasses to establish and about two-years to suppress weeds. With active management, these strips will require mowing, haying or grazing. Mix includes Tall, Western, Slender, Green (AC Saltlander) Wheatgrasses and Russian Wildrye at 1.5 to 1.6 pounds of each grass per acre. If the strips are adjacent to a native rangeland, then Green Wheatgrass (AC Saltlander) should not be included in the mix and instead seeding rate for the other four species should be increased to 2 pounds per acre. That is suggested as AC Saltlander is a cross between bunch and quack grasses and is rhizomious. This can lead to being invasive. In addition, 1 to 2 pounds of a winter-hardy alfalfa variety can be added to the grass mix. It has been observed at two sites, that alfalfa started establishing three-years after planting. That, however, may not work at all sites. There are two optimum times for planting these grasses: early to mid-May and dormant planting in October.

By planting strips of these mixes, white saline areas can be contained. Also, this remediation strategy may take three to five years or even longer if dry weather persist. Producers can either mow these strips, sell as hay or graze them. In addition, by planting these strips onto these saline and sodic areas, producers may be able to get payments from the government programs. For details, please visit your local Natural Resources Conservation Service office.

With time, these headlands might be planted with crops like wheat, canola and corn and soybean again. However, under drier weather even after establishing these strips, these area may still be one of the worst as there will not be enough rain or snow melt to push the salts and sodium out of the root zone despite lower groundwater depths. Water caused these issues and water will help with remediation. With established perennial salt-tolerant covers, however, remediation of these areas will still continue.

Fig 4 PLSC

There are few more strategies that could be considered as management options:

 

  • Tiling entire fields is often considered as a first-option to lower salt levels. However, under dry weather groundwater depths lowers naturally and there is no need for most of these areas to be tiled. In addition, research has shown that salt levels increased under dry weather on tiled land. It will make more sense to tile these areas once weather pattern starts getting wet again.
  • Soil amendments such as gypsum that are applied to remediate sodicity will also require decent rain to get dissolved and add free calcium (Ca2+) to the soils. Under dry weather, that process will be very slow.
  • In case of not planting salt-tolerant annual crops or perennial grasses, some weed species may grow on these saline-sodic areas. If managed properly, weeds can be mowed before they go to seed to reduce evaporation.

 

Naeem Kalwar

Extension Soil Health Specialist

 

Dr. Thomas F. Scherer

Extension Agricultural Engineer

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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