Case Studies: Champ H
Champ H is located south of Montréal. The aerial photo shows that Champ H comprised two fields. The northern field has a section that is not cultivated as it has many stones and has rock outcrops. This field has considerable differences in elevation (Figure 1 ) with a height difference of 3.7 m in the field. The 8-ha field had a sampling density of 10 samples per ha and a total of 82 samples were taken on this field. Figure 1 shows the soil-sampling grid for the field. The field was hand-sampled for grain corn yield at each of the 82 points. There are no yield maps from previous years.
Phosphorus & Potassium
The phosphorus distribution pattern based on the 82 sample points is given in Figure 2.. The average P level was 148 kg/ha with a range of 66 to 270 kg P/ha. The recommended P fertilizer rate is 40 kg P2O5/ha for corn. Based on this map, 34% of the field received the recommended fertilizer rate while 21% was under-fertilized and 45% of the area was over-fertilized. Figure 3 shows a map based on six randomly chosen sample points, which is a number closer to what a commercial operation would use. In this case, based on the 6-point interpolated map, 30% of the area would get the recommended fertilizer rate while 21% would be under-fertilized and 49% would be over-fertilized. A greater portion of the field was estimated to have a level of P greater than 150 kg/ha. Figure 4 shows the potassium distribution in the field. The average K level was 309 kg/ha with a range of 94 to 696 kg/ha. These K values are relatively high for a loam to a clay loam soil. The field is close to the dairy barn and has received frequent manure applications. Figure 5 shows the K distribution map based on the same six sample points. The K distribution pattern is similar in the two maps (six points versus 82 points). In this case six points accurately represent the field K level, but K is not considered to be an environmental problem.
Crop Yield Patterns B Unaltered
Figure 6 gives the yield map based on 82 sample points. The average yield was 11.8 t/ha with a range of 4 to 16 t/ha. The yield patterns are not correlated with the P or K distributions. None of the other measured soil parameters shows any relationship with the yield.
Crop Yield Patterns B Normalized
Figure 7 shows the normalized yield and in 1999 57% of the field had a yield within +/- 10% of the average and 24% of the field had a yield greater than 10% of the average yield. Again, there are no clear reasons or patterns to explain why certain zones had a high yield or why 19% of the field had a yield less than 90% of the average.
Spatial, Temporal and Classified Management Maps
These management maps require several years of yield data that were unobtainable for this field.
Soil Physical and Nutrient Maps
Figure 8 shows that the P saturation % is average to high, with 75% of the field between 5 to 10%. About 25% of the field is in the high zone and this could be a future problem with regards to P applications whether from fertilizer or manure. The aluminum content (Figure 9 ) varies widely across the field, from 480 to 1300 mg/kg of soil. The Al level is based on the parent material and is an inherent soil characteristic, that is, the levels cannot be modified by the producer. The calcium (Figure 10 ) and magnesium (Figure 11 ) levels are sufficient for crop growth and no remedial measures appear necessary. The organic matter distribution is given in Figure 12. and levels vary from 2.5 to 7.5 % across the field. The organic matter content does not correspond to the sand % shown in Figure 13 (normally a high sand % would have a low organic matter %). However the higher clay % in Figure 14, is correlated with a higher organic matter %. Organic matter binds to clays and is protected from decomposition. The silt % does not show any relationship with other soil variables (Figure 15 ). The soil pH (Figure 16 ) is good for corn growth and 95% of the field had a pH greater than 6.2. Ammonium-N levels (Figure 17 ) were low (less than 9-kg ammonium-N/ha) and 90% of the field had a nitrate-N level of 16 kg/ha (Figure 18 ). The N levels were determined on soil samples taken in July/00. The soil moisture contents given in Figure 19 show higher levels associated with the higher clay values.
Conclusions & Recommendations
The field does not have any strong zones of high or low yield that can be explained by any of the parameters measured. Compared to the other case studies, this field had a high grain corn yield average and 81% of the field area had good to high yield levels. There could be a problem with the P saturation % as it is approaching the critical level of 10% but the soil test P average is less than 250 kg P /ha. Fields that have greater than 10% P saturation and greater than 250kg P/ha has restrictions on the amount of P applied in manure or fertilizer.