strate for the soil microbial biomass and has the potential to be an agricultural soil amendment that provides Oily food waste containing high concentrations of fat, oil, and a beneficial source of organic matter. Higuchi and Kurigrease (FOG) is produced by the food service and food production/ processing industries. Fat, oil, and grease have a high C/N ratio (90:1)

With current agricultural practices the amounts of fertilizer N applied are frequently more than the amounts removed by the crop. Excessive N application may result in short-term accumulation of nitrate nitrogen (NO3-N) in soil, which can easily be leached from the root zone and into the ground water. A management practice suggested for conserving accumulated NO3-N is the application of oily food waste (FOG; fat + oil + greases) to agricultural soils. A two-year field study (1995-1996 and 1996-1997) was conducted at Elora Research Center (43 degrees 38' N, 80 degrees W; 346 m above mean sea level), University of Guelph, Ontario, Canada to determine the effect of FOG application in fall and spring on soil NO3-N contents and apparent N immobilization-mineralization of soil N in the 0- to 60-cm soil layer. The experiment was planned under a randomized complete block design with four replications. An unamended control and a reference treatment [winter wheat (Triticum aestivum L.) cover crop] were included in the experiment to compare the effects of fall and spring treatment of oily food waste on soil NO3-N contents and apparent N immobilization-mineralization. Oily food waste application at 10 Mg ha(-1) in the fall decreased soil NO3-N by immobilization and conserved 47 to 56 kg NO3-N ha(-1), which would otherwise be subject to leaching. Nitrogen immobilized due to FOG application in the fall was subsequently remineralized by the time of fertilizer N sidedress, whereas no net mineralization was observed in spring-amended plots at the same time.

Rashid, M. T., Voroney, P. and Parkin, G. 2005. Predicting nitrogen fertilizer requirements for corn by chlorophyll meter under different N availability conditions. Can. J. Soil Sci. 85: 149-159. Nitrogen management strategies that enhance fertilizer use efficiency and maximize profitability in corn require a rapid and accurate method to determine the crop N needs of current hybrids. The objective of this study was to evaluate the potential of a portable chlorophyll meter for predicting N fertilizer requirements for corn grown under varying levels of N availability. Several crop management treatments were imposed in an attempt to create conditions ranging from low N availability (oily food waste application in spring and fall, application at different rates in spring) to high N availability (continuous fertilized corn, winter wheat cover crop). Different corn hybrids were sown at different sites (21 site yr) and varying N fertilizer application rates were applied. Chlorophyll meter readings (CMR) were taken at the 5th to 6th leaf stage (V 6 ) using a SPAD-502 chlorophyll meter. The crop management treatments, corn hybrids and their interaction significantly affected the chlorophyll meter readings. A high inverse correlation between chlorophyll meter readings and maximum economic rate of nitrogen (MERN) was observed (r = -0.87). The main new and unique aspect of our research is the development of a linear model for using chlorophyll meter measurements to make N fertilizer recommendations (MERN = 348.47 -8.5304 × CMR) for corn production under varying degrees of N availability in Southern Ontario. L'étude devait évaluer l'utilité d'un appareil portatif servant à doser la chlorophylle pour établir les besoins en engrais N du maïs cultivé dans des sols contenant une quantité variable de N assimilable. Les auteurs ont recouru à diverses pratiques culturales pour engendrer les conditions voulues, soit une faible (application de déchets alimentaires huileux au printemps et à l'automne, variation du taux d'application au printemps) à une grande quantité (fertilisation continue, culture-abri de blé d'hiver) de N disponible. Ils ont semé divers hybrides de maïs à différents endroits (21 sites-années) et appliqué un taux variable d'engrais azotés. Ensuite, ils ont dosé la chlorophylle au stade de la 5 e -6 e feuille (V 6 ) avec un lecteur SPAD-502. Les pratiques culturales, l'hybride et leurs interactions affectent significativement les relevés. Les résultats obtenus avec le lecteur présen-tent une très forte corrélation inverse avec le taux d'application maximal économique d'engrais azoté (TAME) (r = -0,87). La principale innovation et le caractère unique de cette étude consistent en l'élaboration d'un modèle linéaire utilisant la concentration de chlorophylle pour formuler des recommandations sur l'application d'engrais azotés (TAME = 348,47 -8,5304 x quantité de chlorophylle) pour la culture du maïs selon la quantité de N disponible dans le sud de l'Ontario.

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Soil and plant indices of soil fertility status have traditionally been developed using conventional soil and crop management practices. Data on managing N fertilizer for corn (Zea mays L.) produced on soils amended with C-rich organic materials, such as oily food waste (OFW) is scarce. Identification of a reliable method for making N fertilizer recommendations under these conditions is imperative. The objective of this research was to evaluate soil NO(3)-N (0- to 30-cm depth) at preplant and presidedress (PSNT) times of sampling for predicting N requirements for corn grown on fields receiving OFW. Experiments were conducted at two locations in Ontario, Canada over 3 yr (1995-1997) where OFW was applied at different rates (0, 10, and 20 Mg ha(-1)), times (fall and spring), and slope positions (upper, mid, and lower) within the same field. Presidedress soil NO(3)-N contents were higher compared with preplant time of sampling under all OFW management conditions. Corn grain yields were significantly affected by OFW management and N fertilizer application rates. Maximum economic rate of N application (MERN) varied depending on OFW management conditions. Presidedress soil NO(3)-N contents had a higher inverse relationship with MERN (r = -0.88) compared with soil NO(3)-N at preplant (r = -0.74) time of sampling. A linear regression model (Y = 180.1 - 8.22 NO(3)-N at PSNT) is proposed for making N fertilizer recommendations to corn grown on soils amended with OFW in this geographical region.