M. A. Schmitt

Performance of dicyandiamide in the north central states

Abstract The effectiveness of the nitrification inhibitors, nitrapyrin and dicyandiamine, in reducing nitrogen loss from soil and preventing reduction in crop yield was evaluated in field studies conducted over dozens of site years in Illinois, Iowa, Minnesota, and Wisconsin on corn, wheat, and a vegetable crop, potato. Both chemicals were effective in retarding the nitrification of ammoniacal fertilizers, including nitrogen from liquid animal manures, but this inhibitor did not always result in yield increases above that obtained with equivalent amounts of nitrogen applied without inhibitor. Greatest benefits for nitrification inhibitor use was obtained on coarse‐textured soils under conditions that were conducive to nitrate nitrogen loss when nitrogen was applied at rates not considered to be excessive.

A Manure Management Survey of Minnesota Swine Producers: Effect of Farm Size on Manure Application

There is a national trend for swine enterprises to increase in size due to cost efficiencies associated with economies of scale. This study was performed to evaluate the effect of farm size on manure application management for a survey of 391 swine producers in Minnesota. There was a statistically significant effect of farm size on almost all of the variables evaluated. As farm size increased: a) more manure was handled in the liquid form; b) more farms analytically tested their manure; c) more farms calibrated their application equipment; d) less manure was applied in the summer and winter months; e) broadcast manure applications decreased while injected manure increased; and f) more farms kept records of manure applications. However, while the management practices associated with the larger farms were better correlated to recommended practices, the ratio of animal units to the number of acres owned and available for manure application increased steeply as farm size categories went from small to large.

Effect of manure on accumulation of dry matter, nitrogen, and phosphorus by soybean

Manure application for soybean [Glycine max (L.) Merr.] production is being considered by livestock producers, but the manures influence on dry matter (DM), nitrogen (N), and phosphorus (P) accumulation is not well documented. The objectives of this study were to measure N, P, and DM accumulation patterns and quantities by three genetically-different soybean varieties. Two preplant, sweep-injected manure application rates and a control were main plot treatments and three soybean varieties were subplots at seven experimental sites in 1996 and 1997. Starting in mid-June and continuing on a 15-d schedule until maturity, whole-plant samples were collected, dried, weighed, and analyzed for N and P. Plant DM increased with increasing manure rates at each sampling after mid-June. Nitrogen concentration differences among manure rates were greatest early in the season and diminished with time, whereas P concentration differences were consistent throughout the sampling period. Compared to the control treatment, manure resulted in an average of 25% more N accumulation at the first sampling date, 35% more at the second sampling, 42% at the third sampling, and then steadily decreased to a 10% increase at the final sampling date. Similar to N accumulation, mean P accumulation differences between the control and the manure treatments increased to 27% at the third sampling and then gradually decreased to 14% by the final sampling date. The overall effect of variety was minimal, yet statistically significant, and interactions between manure rate and variety were not found. Applying manure for soybean increased end-of-season accumulation of DM, N, and P by 9, 10, and 14%, respectively, compared to the non-manure treatment.

Extractable Phosphorus Following Soil Amendment With Manure From Swine Fed Low-phytate Corn

Manure application rate recommendations have been based almost exclusively on nitrogen (N) management considerations, which can result in over-application of phosphorus (P) and its accumulation in soil. Low-phytate (LP) corn (Zea mays L.) was introduced into swine (Sus scrofa domesticus) feed to reduce the amount of P in manure. Unlike ruminants, swine cannot utilize phytate, the major form of P in normal hybrid corn. The objectives of this study were to determine extractable P following swine manure application from different manure sources and compare the relative P availability of LP-manure to standard (S) manure. A laboratory incubation study was conducted using a Waukegan silt loam, a Verndale sandy loam soil, and five levels of total P (Pt) from three P sources (KH2PO4, S-manure, LP-manure). Extractable P from manures of swine fed low-phytate corn and standard corn diets were compared with a soluble P (KH2PO4) source. Slope ratio procedure was used to determine a phosphorus availability index (PAI). The effect of the P application rate on extractable Bray-1 P was linear (r2>0.97). Small but significant P mineralization was observed for the Verndale sandy loam soil. Mineralization of organic P was detected only at the highest LP-manure application rate for the Waukegan silt loam soil. Relative to KH2PO4, the LP-manure and S-manure had PAI of 0.55 and 0.61, respectively. Swine manure P availability was about 60% that of the KH2PO4 source for both manure sources. The total P concentration for the LP-manure was 42% lower than that for the S-manure. The important factor in the difference between manure sources is the 42% lower total P content for the LPmanure, not a difference in availability. Further evaluation of available P from LP-manure is needed under field conditions.

A Manure Management Survey of Minnesota Swine Producers: Summary of Responses

Manure’s impact on the environment is a concern for both livestock producers and the general public. A survey of Minnesota swine producers was conducted to determine current manure handling systems and manure management practices. A questionnaire containing 36 questions was mailed to 699 Minnesota swine producers. Questions focused on manure collection, storage, and application systems, dead pig disposal, and swine housing system. Survey responses indicate: a) most producers market 2,000 pigs per year or fewer; b) most producers handle some manure as a solid; c) the majority of producers are not testing manure, calibrating manure application equipment, or keeping records of manure applications; d) surface application of manure is more common than subsurface injection; e) rendering and burial are the most common means of dead pig disposal.

Extension programming for teaching manure management to farmers

livestock manure. Others have had to change practices because of public concerns for water quality. In addition, the ever-expanding size of new livestock facilities makes them much more likely to run afoul of local zoning ordinances because of odor and other aspects of manure storage, handling, and application. The water quality dimensions of manure management are magnified in Minnesota by state-level feedlot regulations that are commonly regarded as being among the toughest in the United States. All farms having over 10 animal units in confinement at any time during the year are included. Individual counties are allowed to

MODELING OF SUGARBEET QUALITY VARIABLES FROM CANOPY SPECTRAL INDICES IN A FERTILITY TRIAL

Sugarbeet quality varies inversely with N fertility, while gross yield varies positively with N. Existing models of yield from remotely sensed data do not consider crop quality. A fertility trial was used as the basis for a canopy reflectance study to correlate quality variables to canopy characteristics. Sugarbeet canopy reflectance and radiance were measured with a portable spectroradiometer, and from airborne images of the trial plots. Canopy data were collected five times from early August to early October of 1999. Linear regression models were used to correlate canopy indices to sugarbeet quality variables on each date. Both a green NDVI and the conventional NDVI indices showed strong correlation to recoverable sucrose concentration in sugarbeet roots. Correlations to harvest quality in October were highest in spectral measurements taken in early to mid–August. Other quality variables including root concentrations of sodium, potassium, and amino–N were poorly correlated to spectral properties of the canopy. The results suggest that a single image of a field in August could provide spatial indication of variability in root quality.