Nitrogen cycling and budget in crop rotations as influenced by preceding crops and N fertilization

Non-Peer Reviewe

Response of barley yield and yield components to nitrogen rate under low and high input management systems

Increasing rates of nitrogen (N) fertilization may increase disease and lodging in cereals. As a result, use of high-input management (HIM) systems, which use growth regulators to control lodging and fungicides to control disease, may allow a greater increase in yield due to N fertilization than occurs in conventional low input management (LIM) systems. The study was conducted to determine the influence of two management systems on the response of yield and yield components of barley (Hordeum vulgare L.) to N fertilization and to determine if use of a HIM system was cost-effective under southern Ontario growing conditions. Barley, cv. Leger, was grown at eight rates of N fertilization under either HIM or LIM systems in 10 environments in southern Ontario. The response of grain and straw yield to N rate was not significantly different between management systems; however, the maximum economic yield occurred at a significantly higher N rate under the HIM system (90 kg N ha−1) than under the LIM system (71 kg N ha−1). The number of heads m−2 was higher under the HIM system than under the LIM system whereas the reverse was true for grains head−1. Increased N rate resulted in increased 1000-grain weight under the HIM system but had little influence on 1000-grain weight under the LIM system. Over the duration of the study, the increased revenue obtained under the higher input management system was generally less than the cost of the added inputs used, emphasizing the need for threshold values which producers can use to determine when crop protection inputs are likely to be cost-effective. Key words: Fungicide, growth regulator, seeding rate, nitrogen, barley </jats:p

Interaction of the rate of P and K fertilization on the yield response of three forage legume species

A response surface model was used to study the interaction between the rate of P and K fertilization on yield of three legume forage crops: alfalfa (Medicago sativa L.), trefoil (Lotus corniculatus L.), and red clover (Trifolium pratense L.). The results suggest that the soil test calibration recommendations developed for P or K on forage legumes are relatively insensitive to the rate of the other nutrient applied. Key words: Alfalfa, red clover, trefoil, soil test calibration, response surface model </jats:p

Yield and protein response of hard red winter wheat to rate of nitrogen fertilization and previous legume crop

The purpose of the study was to determine the influence of a previous legume or non-legume crop on the yield and crude protein response of hard red winter wheat to the rate of N fertilization. The average N requirement for the maximum economic production of wheat was reduced from 69 kg N ha−1 following corn to 0 kg ha−1 following alfalfa. Crude protein concentration was as much as 2% higher following alfalfa than corn; however, an average of 144 kg N ha−1 following corn and 59 kg N ha−1 following alfalfa was necessary to achieve the optimum level of 13.5% crude protein in the wheat.Key words: Corn, alfalfa, ICM </jats:p

Growing season nitrogen dynamics in manured soils in south coastal British Columbia: Implications for a soil nitrate test for silage corn

Spring soil nitrate and ammonium dynamics in south coastal British Columbia soils were examined with respect to the potential to develop a soil nitrate test for silage corn (Zea mays, L.). Soil nitrate and ammonium contents were measured to 90 cm depth in two soils from April to July of two growing seasons. Treatments included a control, spring application of either 300 or 600 kg total N ha−1 as liquid dairy manure, or 200 kg N ha−1 as inorganic fertilizer. Significant amounts of ammonium were present until late May following manure and until mid-June following fertilizer application, requiring simultaneous determination of both nitrate and ammonium concentrations to assess soil inorganic N contents during this period. Most of the changes in soil nitrate over time occurred in the top 30 cm, suggesting that sampling to 30 cm depth would be sufficient in most cases for a soil nitrate test in this region. Most of the increase in soil inorganic N associated with the spring application of manure occurred by 1 June. A soil nitrate test in early to mid-June when the corn is at the six leaf stage appeared to be most suitable for use in south coastal British Columbia to determine if additional fertilizer N is required. A sample taken at this time will measure soil nitrate contents just before the period of rapid corn N uptake, after most of the additional inorganic N associated with spring manure application is already present in the soil as nitrate, and after nitrification of the manure ammonium has occurred. Key words: N recovery, preplant nitrate test, pre-sidedress soil nitrate test </jats:p