Agribusiness and government agencies have embraced the 4-R concept (right form, rate, time, and place) to improve nutrient management and environmental quality. No-tillage is also a major component of nutrient efficiency. Over the past three decades, innovators and scientists have developed:

1) machinery to make variable-rate nutrient applications,

2) soil and tissue sampling strategies to better define spatial variability,

3) yield-monitoring harvesters to spatially quantify grain production,

4) remote and proximal sensors to quantify crop vigor during the growing season,

5) soil sensors and water monitoring devices to better characterize soil properties, and

6) statistical procedures to analyze spatial data.

These technologies all embrace global positioning systems (GPS) and rely heavily on geographic information systems (GIS) to display and store the temporal and spatial information. The question at hand… Does the complete adoption of the 4-R technologies, with uniformly improved stored soil moisture, represent the ultimate in terms of precision agricultural production? Are there opportunities for further advancements and innovations?

Considering the above advancements and opportunities they represent, several seed corn companies have been developing cultivars that fit within the 4-R concept and have begun to market drought tolerant hybrids. In terms of the nutrients required to achieve acceptable yields, it is appropriate to more carefully examine the 4-Rs and tillage for their level of sophistication. This is because various aspects of the 4-Rs are inter-related and therefore constitute a challenge for innovators that have the knowledge and expertise to integrate the engineering, chemical, and agronomic aspects of nutrient applications. Minimizing tillage obviously improves the uniformity of the land and the water distribution in the root zone.

Nutrient application issues that deserve further attention include:

1) the uniformity of fertilizer delivery across the width of the applicator (or segment thereof),

2) ways to utilize chemical reactions in the soil to optimize timely nutrient availability and minimize losses, and

3) strategic placement of nutrients relative to rooting patterns and changing soil pH.

Insuring uniform distribution of liquid fertilizers within an applicator is critical and yet can be highly problematic with materials like anhydrous ammonia. To complicate the issue, this primary nitrogen fertilizer source converts from liquid to gas as pressure is reduced. The bubbling and frosty nature of Anhydrous Ammonia flow makes accurate metering virtually impossible. One combined solution is to pressurize the Anhydrous Ammonia system (use a pump, a high pressure manifold delivery system and a series of orifices to keep the material in a liquid form). The system maintains liquid streaming flow by forcing the liquid through a series of carefully-sized orifices so that the pressure does not drop below tank pressure until the point of injection in the soil. Pressurizing the liquid with a hydraulically-controlled positive displacement pump and orifices makes it possible to quickly alter the delivery rate to the target location and in the process address one aspect of Place (uniformity across the applicator based on the specific potential of the land) and a special aspect of Rate (desired application rate which is assured by the low CV application…or absolute uniformity).

Chemical reactions in soil can be both advantageous and problematic. In the case of nitrogen (N), nitrification is the biological process that transforms ammonium to nitrate and thus makes N loss via leaching a threat to the environment. Reducing the rate of nitrification can be accomplished with nitrification inhibitors and thereby better synchronize soil N availability and crop N need during the growing season. Using compounds like ammonium thiosulfate as a nitrification inhibitor also provides sulfur (S) to the crop and frees up micronutrients. Further, injecting small amounts of an organic substance like Humic and Fulvic acid has the potential to protect nutrients from adsorption to soil particles. Rather, the nutrients remain in a quasi-immobile state in the soil so they can be more readily accessed by plant roots.

Placing nutrients in proximity to roots is an important aspect of crop vigor and beating back drought stress. Developing deeper rooting allows the plant to improve it’s survivability in annual cropping. Use of starter fertilizers is common in some areas and fall application of anhydrous ammonia is popular in some situations. For the most part, the majority of N fertilizer applied to corn in the U.S. is made in a single band (under the row as with strip-tillage or between the rows). There is a perceived and real benefit to consider dual-band availability of nutrients. This increases root access to nutrients, especially on infertile soils or at times when crops are growing rapidly and nutrient uptake rate is relatively high.

Field strip studies will be presented that compare current N fertilizer technologies with advanced liquid application systems the address uniformity, rate, placement and no-tillage. Economic analyses favor advanced application systems in terms of fertilizer savings, yield, and profitability.