Manure placement depth impacts on crop yields and N retained in soil

Area of Science:

• Soil Science
• Agronomy
• Environmental Science

Background:

• Manure application depth significantly influences nutrient availability and crop performance.
• Understanding nitrogen (N) dynamics in soil is crucial for optimizing fertilizer management and minimizing environmental impacts.

Purpose of the Study:

• To evaluate the effect of deep (45 cm) versus shallow (15 cm) manure injection on crop yield and soil nitrogen retention.
• To assess the impact of manure placement depth on soil water infiltration and nutrient distribution over time.

Main Methods:

• Experimental field trials comparing deep manure injection, shallow manure injection, and conventional fertilizer management.
• Monitoring of soil inorganic N (NO3-N, NH4-N), total N, water infiltration, and crop yields (soybean, corn) over 30 months and three growing seasons.
• Analysis of N distribution in soil profiles following different injection depths.

Main Results:

• Deep manure injection resulted in higher soil inorganic N concentrations (NO3-N and NH4-N) in the long term compared to shallow injection.
• Deep injection led to increased total soil N over 30 months and significantly improved corn yield when nitrogen was limiting, attributed to enhanced N use efficiency.
• No significant impact on soybean yield was observed, but higher corn yields suggest benefits for N-demanding crops.

Conclusions:

• Deep manure injection (45 cm) is a promising technique for improving nitrogen use efficiency and crop yields, particularly for corn, in glacial till soils.
• This method can potentially reduce nitrogen losses through volatilization, leaching, and denitrification, thereby improving water quality.
• The effectiveness of deep manure injection may be limited in rocky glacial outwash soils due to subsurface penetration challenges.