Measuring the drought impact on your 2012 yields may have been easy, although the psychological impact cut to the quick. However, more difficult may be measuring the impact of the drought on your main asset, the soil on your farm. Sure, it dried out as heat increased and rain diminished, but how was it impacted beyond the loss of moisture?
The soil itself suffered physically and that is something that needs your attention. After all, it may have a $15 to $20 thousand dollar per acre value. With that value you cannot afford to have it break, because baling wire and duct tape won’t help much.
The impact of a drought is typically measured in terms of loss of moisture, and the weekly Drought Monitor from the University of Nebraska kept everyone informed of whether they were in the yellow, brown or red territory, and how bad it was in their state. But just like moisture being only one characteristic of grain, it is only one characteristic of the soil.
Grain can be dried to manage moisture, and soil moisture can be managed to some degree as well. But how is that done and what other issues did the drought create? Those questions are addressed by Iowa State University soil scientist Mahdi Al-Kaisi and a number of his colleagues in the Journal of Soil and Water Conservation.
The Iowa State researchers reported that drought conditions, which were pervasive throughout their state, caused fracturing and cracking in the upper 6 to 15 inches of the soil, with the potential for deeper cracking depending on soil minerals and clay content. They report soil crusting was a problem as surfaces hardened where conventional tillage had been used and where there was poor cover from either residue or crops.
Problems began to appear in the winter of 2011-2012 where a lack of surface cover caused deterioration of soil aggregates, allowing cementation to occur that impacted the relationship between soil moisture and plant roots.
Damage to the soil itself
Al-Kaisi reports that soil management practices can improve the way water is stored in the soil, and when available for plants, it will reduce the impact of the drought. Such management practices will enhance the soil aggregation, water storage, water infiltration, and reduce potential erosion, all with management techniques:
- Tillage of dry soil damages soil structure, and when moisture is available the moisture will not be held in the soil and will result in erosion. Tillage also reduces the ability of moisture to reach the subsoil where it would be available for crops in time of moisture stress. Consequently, he says either no till practices or minimum tillage will decrease the impact of a drought.
- Residue management can play a significant role in sustaining a good soil structure. Surface residue retards erosion in heavy rain, and good residue will allow more water to enter and remain in the soil profile. He says allowing 12 in. of corn stubble to remain will achieve those objectives. He adds, “Upright residue traps and stores moisture effectively and slows downslope water movement.”
- Cover crops will protect soil from erosion, improve the soil structure, increase organic matter, and reduce nutrient loss. But he acknowledges that dry conditions from a drought may challenge the ability to get a cover crop established.
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