Phosphorus and suspended solids (SS) contents in tile discharge from two southwestern Ontario clay soil drainage experiments were measured over a 2‐y period. For continuous corn (Zea mays L.) plots, loads of SS and total P were 407 and 0.88 kg ha−1 y−1, respectively. Suspended solids and total P loads from drains beneath permanent sod were 97 and 1.85 kg ha−1 y−1, respectively. Comparison of these results with limited data on P and SS loads in surface runoff indicated that >50% of the total P load from these nearly level plots may be lost via subsurface tile flow. Overall, 34% of the total P load from subsurface drains was sediment‐associated. Furthermore, crop cover, P fertilization rate, and tile drain depth were found to significantly affect dissolved P export. Dissolved P concentrations in effluent from permanent bluegrass sod exceeded those from continuous corn and rotational plots. Subsurface sediment and sediment‐associated P loads were highest from continuous corn. Greater soil cover over the tile line decreased both sediment and P concentrations. Sediment‐associated P concentrations increased with P fertilization rate at one of the experimental locations.
Liquid dairy cattle manure was applied at three rates (224, 560 and 879 kg/(ha∙yr) of manure nitrogen (N)) and four different times: in the fall after harvest of silage corn, before seeding, half in the fall and half before seeding, or in winter to continous corn grown on sandy clay loam for 5 yr. Two other plots were included: one received chemical N-P-K fertilizer at recommended rates, and one received neither fertilizer nor manure. Over the 5-yr study, soil organic carbon increased in the surface layer of the high-rate plots, but decreased in the chemically fertilized plot. Soil inorganic N contents measured at harvest in the 0- to 120-cm layer of the manured plots were related to both cumulative and annual N inputs. Bicarbonate extractable phosphorus in the 0- to 15-cm layer increased each year in the medium- and high-rate plots and exceeded 90 μg/g in the high-rate plots after 5 yr. Exchangeable potassium levels increased singificantly in the plow layer of the medium- and high-rate plots. Smaller accumulations occurred in the winter-applied plots than in the fall- and spring-applied plots. Uptake of nutrients by the corn crop increased with manure rate, but generally was not affected by time of application.
Strip‐intercropping soybean (Medicago sativa L.) with corn (Zea mays L.) decreases yields in soybean border rows. Separating corn and soybean with a small grain strip could decrease competition for soybean and improve overall yield. This study was conducted to determine the effect of a small grain strip on corn and soybean performance and on soil water content in the corn strip. Corn and soybean were strip‐intercropped (rows running north‐south) with oat (Avena sativa L.) in 1991 and barley (Hordeum vulgare L. emend. Lam.) in 1992 on a ridge‐tilled Dalhousie silt loam (fine, mixed, mesic Typic Endoaquoll) in Nepean, Ontario. Both years, plant height varied among corn rows. In 1992, plant development was faster and grain moisture at harvest was lower in corn border rows than in non‐border rows. In 1991 and 1992, soil water was depleted earlier in the corn and small grain interrow than in the corn and soybean interrow. In 1991, a hot and dry growing season, yield of the corn row next to small grain was 20% lower than that of other corn rows. In 1992, a wet and cool growing season, both corn border rows yielded yielded 26% more than nonborder rows, partly due to increased number of ears per plant. Both years, soybean yield in the row bordering small grain was similar to that of nonborder rows but yield in the row bordering corn was 18% lower than that of nonborder rows. Including a small grain in corn and soybean strip‐cropping can be beneficial if soil moisture is not limiting. Research Question Farmers who plant corn using strip‐intercropping with soybean often attribute high yields in the corn border rows to improved light interception. They also attribute low soybean yields in rows next to corn to light competition from the corn plants. Thus, some farmers have thought of including a small grain crop in the soybean‐corn strip intercropping system to improve light conditions for soybean. During dry growing seasons, however, competition for water from the early‐developing small grain may affect corn, which has a high demand for water later in the season. This study was undertaken to determine the effect of strip‐intercropping corn with soybean and a small grain cereal on (i) corn row and interrow water content, (ii) corn height and development, and (iii) corn, soybean, and small grain yield. Literature Summary Scientific literature has consistently documented soybean yield decreases and corn yield increases in corn‐soybean strip‐intercropping systems in North America, although the extent of the yield increases or decreases can be variable. Sometimes, corn yield increases can be observed only on very narrow strips of less than three rows. In addition, the optimal strip width for corn at a specific location can vary annually, indicating that strip‐intercropping performance can be affected by weather conditions. An experiment in eastern Nebraska comparing strip‐intercropping of corn and soybean under dryland and irrigated conditions demonstrated that soil water availability is important in achieving high corn yields. ...
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