Drought Planning Considerations
Drought Planning Considerations
It is important to consider negative impacts within a cropping system during a drought.
Fields may be in less than ideal condition and crops may be suffering from a multitude of stressors including:
- Tilled fields likely had a flush of microbial activity, releasing a considerable dose of nutrients when there was moisture in the soil, thus was available to plants early on. These nutrients may have been used up quickly. Growing plants may experience stress later in the growing season due to lack of nutrients or adequate moisture. Field scouting to identify deficiencies will be important.
- No-till systems typically do not have this early flush, but have a more gradual increase in soil respiration. This gradual increase in respiration releases the nutrients in a “slow-release” fashion. This slow release usually is a good thing, but in times of drought and hot dry weather, biological organism activity slows and decomposition of organic matter is reduced, thus nutrients are released slower or not released at all. Once again, field scouting to identify deficiencies and analysis on whether application of nutrients is appropriate or not will need to be factored in.
With average or normal precipitation, cover crop mixes have the ability to improve soil condition through increasing organic matter, fixing and scavenging nutrients, addressing compaction issues, retaining moisture, etc. With little to no precipitation, the benefit of cover crops, like so many other agricultural processes, is reduced. Those nutrients that were fixed may then become tied up in any remaining plant tissue and are slow to be decomposed and may not be readily released.
Cover crops will use and transpire moisture throughout their growth period until termination. This normal process is predictably beneficial. However, this year those same cover crops that help conserve moisture from late spring rains to help crops through a normal summer may not be able to perform that same benefit. For moisture conservation, we believe that it is critical to achieve and maintain at least 80% ground cover. By doing so, a “micro-climate” is created underneath that canopy, resulting in lower soil temperatures and a reduction in moisture losses due to evaporation.
Much of the nitrogen applied to corn will likely go unused this year. This is precisely the type of year we need a cover crop to trap the much larger residual nitrogen that will be present after a poor crop year; again, adequate moisture will be needed to germinate the cover crop. Deep-rooting, nitrogen-scavenging species should be used in cover crop mixes to capture and retain that nitrogen high in the soil profile, making it available for the following crop.
Droughty conditions have greatly reduced forage availability in many parts of Kansas. Pastures suffered the same challenges as cropland and average production has been decreased substantially.
If pastures have been grazed to the minimum recommended heights, utilization goals or targets have been reached as a percentage of production by weight, or no re-growth has occurred or grasses appear to be completely dormant, producers should put their contingency plan into action. In the absence of a contingency plan which addresses a reduction of forage production due to drought, producers may wish to consider actions such as destocking or marketing targeted herd animals which do not represent long-term herd goals and consider early weaning of calves using alternative forages or pastures set aside for persistent drought conditions. Adequate quality water supplies are also a potential concern during drought and should be monitored regularly to insure safe drinking water conditions are present in grazing areas. When air temperatures are extreme, especially over 100 degrees for extended periods of time, shade may be a necessity during the heat of the day. In an emergency, feeding hay is better than allowing livestock to continuously graze forages and thus severely overgraze, weakening the stand, reducing intake of the animals, and compromising most chances of any good re-growth once adequate moisture returns. However, feeding hay can be expensive and should be considered only after other reduced forage removal actions are considered. Protected plant reserves have more potential of increased dividends of valuable forage for later on.
It is recommended that producers do an inventory of dry matter on hand and estimate livestock forage needs for the present and future. Inventory all grazing livestock and assume at least 3% dry matter needs per body weight per day. Next, walk pastures noting any potential grazing forage present and estimate the amount of available dry matter present per acre. For a rough estimate, figure 250 pounds of dry matter per average acre inch of vegetation present, subtracting what should remain to maintain adequate plant vigor. The total estimated forage from pasture and from hay reserves can then be weighed against livestock requirements. Lastly, estimate the potential for additional plant growth on the conservative side for any possible use or protection of the soil surface. Destocking or allowing for plant growth to occur in the second half of the growing season is important for long-term plant health and vigor.
Alternative forages or annual cover crops such as oats, turnips, and cereal rye can provide good forage for grazing in the fall. Being able to graze annuals during the fall, if conditions allow, will allow more time for re-growth on pastures and rangeland and for plants to rebuild or regenerate root systems damaged or weakened by drought conditions.
Monitor pastures for poisonous plants and forage amounts as livestock graze areas with low available forage. Poisonous plants become more likely to be eaten as hungry livestock search for “something green.”
If possible, grazing is generally more cost-effective than harvesting, moving, and feeding forages to the livestock. Opportunities for grazing and forage should be looked at carefully to ensure the nutritional needs of the livestock will be met with no negative impacts. Drought-stricken crops may become available to be baled, chopped, or grazed. It is extremely important that the producer test all crop material for nitrates. Material with high nitrates will have to be diluted. Check herbicide withdrawals to make sure the crop can be fed to livestock. Fall annuals planted after drought-stricken corn may also be high in nitrates and should be tested prior to feeding or grazing.
For pastures that are not yet dormant or have received enough rain to begin recovery, grazing instead of haying is advisable. Managed grazing may have less of a negative impact because less sod will be opened up and valuable cover will be protected. Pastures with good cover, dry or not, maintain a cooler soil temperature than those with poor cover. This could be the difference in whether the forage survives or not. Cooler soils, even though dry, will be better for plant revival than hotter soils, and cooler soils also slow oxidation of valuable carbon in the soil.
Forages do best when allowed adequate rest after grazing periods, resulting in the plant replacing carbohydrate reserves. Overgrazed pastures take longer to recover once sufficient moisture returns and prolonged damage is detrimental to the stand. Productive forage stands are expensive to establish so care should be taken to prevent damage when possible.
Re-growth during a drought can be very limited and livestock should ideally be allowed to graze to the minimum grazing heights outlined in the Conservation Practice 528, Prescribed Grazing. Most tall cool-season forages have an average minimum grazing height of about 4 inches. This minimum stubble height is needed to sustain the forage plant, its root base, and solar panel. The more leaf material that is left, the more roots are being maintained and the quicker the response of new growth once moisture and improved conditions return.
Rotating livestock allows forages to rest between grazing periods. During drought conditions, longer rest periods are better. If there happens to be heavier amounts of forage available, slowing the livestock down and concentrating them for very short durations will allow them to consume the best forage present, increase utilization, and waste less.
Clearly, the conducting of prescribed fires is anticipated to decline during a drought as planned burns will be delayed until conditions improve. Burning remains a highly effective and economical tool in maintaining/improving rangeland and should still be considered where appropriate. If a prescribed fire is planned, it is critical to check for adequate soil moisture in the profile to better facilitate re-growth. In most soils, the rooting zone should be damp to the touch; and in sandy soils, some excess moisture should be able to be squeezed out. One should also consider the presence or absence of safe prescribed burning conditions. With extended dry periods, natural fire breaks that might be reliable in more average or wet periods may now be unreliable to control or prevent the spread of fire. Heavy fuels such as woody plants or riparian areas containing cool-season forages or leaf litter may readily ignite and make the control of prescribed fires difficult. Relative humidity (Rh) should also be monitored. The lower the Rh, the more likely spot fires will occur. Lower Rh levels will make fuels more easily ignited, rate of spread increased, and control more difficult.
Before seeding an area to grass, soil moisture and site conditions should be carefully evaluated to avoid a potential stand failure. For those areas or practices in which a cover crop is required, it is vital that the cover is of good quality and is as close to that maintainable 80% canopy as possible.
Emergency action should be considered to reduce blowing and drifting soil. This may be observed on all land uses including grazing lands where little or no previous year’s re-growth occurred or was utilized as forage.
Maintaining as much ground cover as possible should be a primary consideration when planning any wind-erosion mitigation action. Ground cover would preferably be living plant material, but previous residue is also effective and as much of it should be left intact on the surface as possible. Planting a cover crop or feed strips should be considered (be certain to have the producer check with their crop insurance representative for any potential conflicts where appropriate). If irrigation is available, it should be properly utilized to support the plant community. Maximizing ground cover may also mean limiting the grazing on “graze-out” wheat, or other stubble. Producers should also be discouraged from burning off their wheat stubble.
Emergency tillage may be necessary on soils with an erodibility factor (I) of less than 134 (non-irrigated I). Soils with an I of 86 to 134 may not respond to emergency tillage depending upon soil moisture conditions and physical properties.
The following file requires Acrobat Reader.
Map - Kansas Soil I Factors (PDF; 4 MB)
Extreme tillage increases wind resistance by roughening the surface of the land. NRCS Conservation Practices 609, Surface Roughening, and 588, Cross Wind Ridges, provide guidance to design this type of activity. Be aware that these practices are temporary and will not likely persist through the entire critical erosion period. Re-application of tillage may be necessary. Tillage on native rangeland is not advised until all other measures have been attempted and failed.
Other measures may be necessary to increase roughness or create obstruction to wind shear. Manure application, mulching and crimping, and/or placement of other obstructions (e.g., large bales) to reduce wind-borne erosion. Follow Conservation Practice 590, Nutrient Management, for manure applications and 484, Mulching, for applying mulch. These methods may be costly, materials difficult to obtain, temporary, and likely only applicable on small fields.
With the present drought conditions throughout the state, be mindful of the minimum moisture requirements for proper soil compaction as listed in the NRCS construction specifications, specifically for earthfill and pipe installation (applies to all pipe types).
- Earthfill: The fill material shall have moisture content sufficient to secure compaction. Adequate moisture will be maintained in the fill material such that, when a ball of material is formed by hand, it will easily maintain its shape and act as a uniform pliable mass
- Pipe Installation: The water content of cohesive backfill material shall be such that, when kneaded in the hand, the soil will form a ball which does not readily separate. For non-cohesive sand and gravel backfill material, water content is not a concern for thin lifts.
If these minimum moisture requirements cannot be met with natural soil moisture by the landowner or contractor, construction is recommended to stop. If construction has to continue, having water available, as well as a means to apply it so that adequate moisture is achieved as described above, is necessary. Please remember that no amount of compactive effort is a substitute for the proper moisture content in the soil when trying to properly compact soil.
Some of the most common types of practices which will be impacted due to poor compaction are pond dams, wetland fills, grade stabilization structures, fill areas in grassed waterways, terraces, diversions, waste storage facility liners and embankments, pipelines, underground outlets, and water and sediment control basin (WASCOB’s). There are some types of practices such as macro-topography for wetlands (excavation) that may be easier to construct due to the dryer soil conditions.