Excess water compromises plant growth and fitness in agricultural systems. Depending on geography, dramatic fluctuations and extreme weather patterns have been observed in Ohio, the United States, and other parts of the world (eg droughts, floods). Research has shown that such events have increased in frequency and intensity over the past 50 years, making farming more difficult.
This is not new to Ohio, the wet conditions would have repeated during the last weeks of the harvest season, starting in April, May and the first half of June 2022. As a result, the harvest did in the face of unfavorable conditions (Figure 1), and farmers started to think about adjusting their decisions for the rest of the season to reduce the impact of the damage.
Reports ranged from waterlogging (i.e. the root system is in anaerobic conditions) to flooded conditions (i.e. the roots and some aboveground vegetation are under water) (Figure 2).
Excess water has negative effects which can range from delaying planting, reducing seed/plant vigor, altering normal growth/development, nutrient losses, water quality issues, erosion soil, reduced nutrient uptake and increased susceptibility to pest and disease pressures.
Each of these conditions can negatively impact early crop establishment, continued growth and development, and ultimately can reduce yields.
Nitrogen (N) is the primary nutrient of concern under waterlogging or flooding conditions. Nitrogen, especially the nitrate form (NO3-), is a highly mobile nutrient in the system (eg soils, plants, water, air) and can be lost due to leaching and denitrification.
Therefore, nitrogen fertilizer applications in maize are often timed (eg, before planting, at planting, after planting) to gain nitrogen use efficiency. Additionally, split applications can avoid losing the season’s N budget due to excessive rainfall.
Ohio’s base nitrogen rate recommendation is from the Corn Nitrogen Rate Calculator (CRNC) found here. The suggested nitrogen rate assumes best management practices for the timing and placement of N. This tool does not provide recommendations for allocations, percentages, sources, or forms to apply.
For apps that haven’t happened yet, here’s a list of tweaks to consider:
Adjusting the timing of nitrogen fertilizer application
This is probably one of the most convenient options. In general, corn needs about 30 lbs of N before the V6 stage, and the rest of the N uptake occurs after this growth stage.
Consider lower pre-sowing rates and plan to apply the rest of the necessary nitrogen later in the season (possibly after flooding) to help minimize losses. Research is underway to develop recommendations for pre-plant rate and lateral coverage combinations. We will share our findings as we go along.
Adjustment of nitrogen fertilizer sources
Some examples are enhanced efficiency fertilizers (EEF) and organic fertilizers. The use of EEFs can prevent and help minimize N losses such as leaching, denitrification and volatilization. Although organic fertilizers are an option, the mineralization of organic sources (eg manure) can be affected by excess water.
Additionally, some research suggests a link between soil potassium (K) levels and N uptake, so ensuring soils are not K-limiting is important to optimize N uptake. study the impact of nitrogen sources on grain yield in the face of flooding, with results to come.
Nitrogen fertilizer placement/method adjustment
Use more efficient locations, for example, 2 x 2. It is necessary to delay fertilizer applications if field conditions do not allow movement of equipment through the field. Starter N can meet the needs of early crops until conditions improve. There may still be an opportunity for nitrogen application later in the season (vegetative medium) with high clearance equipment if the traditional side application windows (V4-V8) are too wet.
Additionally, besides adjusting nitrogen management, a list of other factors to consider include:
The availability of crop insurance has been and continues to be a good risk management tool. Crop insurance payments to farmers in the United States for flood damage averaged $24 billion between 2001 and 2011. As the frequency and intensity of these events increase , the economic losses are expected to be greater at present.
Breeding programs have made efforts to create materials with adaptive traits and acclimatization responses to waterlogging and aerial tissue submersion. At the plant level, ethylene regulation appears to drive one of the adaptive responses. With current records, it is relevant to consider genetic material when ordering seed for the next growing season (i.e. flood-tolerant hybrids).
Use of cover crops
Cover crops provide many services to the system. These services relevant to flood conditions include nutrient retention, better soil structure, nutrient cycling, increased organic matter, reduced soil crusting problems, and increased soil moisture content. biological activity. Note that biological activity is one of the fundamental processes for the cycling of nutrients (i.e. nitrogen) and its transformation into forms available to plants.
However, cover crops can also pose problems with soil drying, harboring negative pests, or causing additional logistical constraints (eg, ending treatment at the right time). Research studies are underway in Ohio to answer some of these questions.
Use of drainage
Drainage systems can be used where excess water is a problem. Drainage systems make it possible to evacuate excess water present in a field. Different options exist; some are sub-drainage and raised bed cultivation. These options are influenced by equipment availability, land topography, cost and labor.
Adjust planting and replanting dates
Late planting under better conditions may prove better than early planting when conditions are not the best (eg wet soils) as an ‘avoidance’ mechanism. Planting may be delayed if corn is used for silage. Depending on when flooding occurs, replanting may also be an option.
However, subsequent plantings would be compromised and could produce low yields due to the shortened growing season. In the event of replanting, it is important to consider adjustments to shorter maturities to increase the chances of success. Recent work from Ohio has suggested that good yields can be obtained with hybrids ranging in relative maturities from 95 to 104, access these results here.
One of the main risks of replanting (i.e. late planting) is that the crop may be frozen in the fall before it has reached physiological maturity. Informations about Maize planting delayed is available here.
Pest and disease monitoring and applications
Seeding problems may be increased due to flooded and waterlogged soil conditions. Some factors that can exacerbate this concern include soil compaction, stunted plant growth, poor seed quality, low seed/plant vigor and crusted soils.
In general, and depending on timing and duration, any presence of pests or diseases can reduce plant growth and yields. To alleviate some of these problems, periodic monitoring and spray applications may become necessary.
A thorough understanding of the morphological, developmental, and physiological responses of maize to waterlogging and flooding is essential to prepare for and adapt to such conditions to minimize yield and economic losses. Some of this work is currently being researched under Ohio conditions; updates and results will be shared as we learn more.