Dennis D. Francis

Comparison of corn leaf nitrogen concentration and chlorophyll meter readings

Abstract Tissue testing of com leaves for nitrogen (N) concentration is not widely used because it is easier and perhaps more economical to apply sufficient fertilizer than to risk a yield reduction because of an N deficiency. Environmental concerns related to N fertilizer will require producers to improve N management practices to reduce the potential for nitrate leaching. Applying fertilizer N on an “As Needed”; basis rather than using a “Lump Sum”; approach has both environmental and economic advantages. Corn leaf disk N concentrations and SPAD 502 chlorophyll meter readings from N rate studies were compared at silking for a variety of hybrids at several locations. Data indicated that chlorophyll meter readings correlated well with leaf N concentrations for a given hybrid and location. Calibration of chlorophyll meters to determine crop N status may not be practical because of the unique “greenness”; characteristics of different hybrids. However, normalization procedures can be used to standardize the ...

Relay cropping for improved air and water quality.

Abstract Using plants to extract excess nitrate from soil is important in protecting against eutrophication of standing water, hypoxic conditions in lakes and oceans, or elevated nitrate concentrations in domestic water supplies. Global climate change issues have raised new concerns about nitrogen (N) management as it relates to crop production even though there may not be an immediate threat to water quality. Carbon dioxide (CO2) emissions are frequently considered the primary cause of global climate change, but under anaerobic conditions, animals can contribute by expelling methane (CH4) as do soil microbes. In terms of the potential for global climate change, CH4 is ~ 25 times more harmful than CO2. This differential effect is minuscule compared to when nitrous oxide (N2O) is released into the atmosphere because it is ~ 300 times more harmful than CO2. N2O losses from soil have been positively correlated with residual N (nitrate, NO3 -) concentrations in soil. It stands to reason that phytoremediation via nitrate scavenger crops is one approach to help protect air quality, as well as soil and water quality. Winter wheat was inserted into a seed corn/soybean rotation to utilize soil nitrate and thereby reduce the potential for nitrate leaching and N2O emissions. The net effect of the 2001- 2003 relay cropping sequence was to produce three crops in two years, scavenge 130 kg N/ha from the root zone, produce an extra 2 Mg residue/ha, and increase producer profitability by ~

Ability for In-Season Correction of Nitrogen Deficiency in Corn Using Chlorophyll Meters

250/ha.