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Crops, as the basic source of essential substances and nutrients, do not always contain sufficient amounts of these essential nutrients to meet dietary requirements. In this review paper, we discussed the effects of fertilization and other agronomic measures on the nutritional quality of cereal, oilseed and protein crops, tuber plants and vegetables. Research indicates that application of N, P, K and S fertilizers generally increases crop yield as well as nutritional quality. For example, fertilizer increased protein concentration in cereals and pulses, oil concentration in oilseed crops, starch concentration in tubers, and concentration of essential amino acids and vitamins in vegetables. However, excessive fertilizer application, especially N fertilizer, can result in undesirable changes such as increases in nitrate, titratable acidity and acid to sugar ratio, while decreasing the concentration of vitamin C, soluble sugar, soluble solids, and Mg and Ca in some crops. Other agronomic measures, such as tillage and crop rotation, organic farming, soil moisture management, and crop breeding and genetic engineering can also have a large effect on food crop quality, though the potential benefits of these measures for improving crop quality has not been fully exploited. Research literature on this subject suggests that more information is needed in order to achieve an increase in the concentration of essential microelements, prevent accumulation of toxic levels of elements such as Cu, Mo, Zn, Ni, Se and nitrate, and other dangerous or toxic substances and elements in crops.

[255][256][257][258][259][260][261][262][263][264][265][266]. New canola cultivars have much higher yield potential than conventional canola cultivars and changes in production practices may be needed to achieve optimum yield from these cultivars. Studies were conducted to investigate the influence of seeding rates (2.8, 5.6 and 8.4 kg ha -1 ), fertilizer level (67% -low, 100% -medium, 133% -high of the commercial recommendation) and fungicide application on growth, dry matter accumulation, seed yield and seed quality using two high-yielding canola cultivars [cv. Quantum, open pollinated (OP), and cv. Invigor TM , hybrid (HYB)]. The studies were conducted from 1999 to 2001 at three sites in the Parkland region of the Canadian prairies. The two cultivars did not differ in their responses to seeding and fertilizer rates, or fungicide application. Plant density was lower for the HYB than the OP because the HYB had larger seeds, with fewer seeds per kilogram. Emergence declined slightly at high fertilizer levels in some site-years due to fertilizer induced seedling damage, but increased with seeding rate. Time to onset of flowering and maturity showed no consistent influence of cultivar, and tended to be somewhat prolonged with an increase in fertilizer levels, but reduced by an increase in seeding rate. On average, the HYB produced 822 kg ha -1 more biomass and 200 kg ha -1 more seed yield than the OP. Sclerotinia stem rot incidence was very low, except at Melfort in 2000, and fungicide application generally failed to benefit the crop. Seed yield was generally increased when seeding rate was increased, with the largest increase occurring from 2.8 to 5.8 kg ha -1 . Seed yield responses to the high rates of seeding or fertilizer only occurred where both inputs were at the highest level, indicating that the optimum level of one was dependent upon the level of the other input. Oil and protein concentration in the seed was higher for the HYB than the OP. High fertilizer levels generally increased the total yield of biomass and seed, and protein concentration in the seed, but usually reduced oil concentration in the seed. Increased seeding rate resulted in a small increase in oil concentration and a small reduction in protein concentration in the seed. Net returns were greatest and least variable for the HYB cultivar. Overall, the HYB performed better than the OP, and the full economic value of high-yielding canola cultivars was only realized when fertilizer and seeding rates were at or above the current recommended rates. . Les recherches se sont déroulées de 1999 à 2001, à trois endroits, dans la région des prairies-parcs des Prairies canadiennes. Les deux cultivars ont réagi de la même manière à la densité des semis, au taux de fertilisation et à l'usage du fongicide. Le cultivar PL a donné un peuplement plus dense que la variété HYB, les semences de ce dernier étant plus grosses, donc moins nombreuses par kilo. La levée a légèrement diminué aux taux de fertilisation les plus élevés à certains sites-années, l'engrai...

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Fall application of N fertilizers is often less effective than spring application in increasing yields of cereal crops in portions of the Prairie Provinces of Canada. This paper reports on five field experiments (and involving three soils) using 15N‐labelled fertilizers to determine the amounts of mineral N lost over the winter by denitrification, leaching, and immobilization. The labelled N fertilizers were applied at 112 kg N ha−1in October in 1974–1975 experiments and in December in 1975–1976 experiments. The plots were sampled to a depth of 120 or 150 cm in late May. In the two 1974–1975 experiments (Malmo sicl soil), KNO3 and urea were mixed into the 0 to 12 cm depth of soil, and (NH4)2SO4 was placed in a band. Recovery of the labelled fertilizer N found in the total soil N was lowest for KNO3 (60 %), next for urea (71 %), the highest for (NH4)2SO4 (84%). The addition of 50 mm of water to the soil, which reduced the soil moisture tension of the 0 to 15 cm depth to less than 33 KPa on fall freezing, decreased the recoveries of KNO3 and urea in the total soil N to 26 and 54%, respectively. There was no leaching below the 60 cm depth. For the three fertilizers, from a 10th to a third of applied N was immobilized. In the three 1975–1976 experiments, the three soil types were, Demay 1, Malmo sicl, and Falun 1. The fertilizers were placed in bands 5 cm deep into the frozen soil. There was little loss of the labelled N from the total soil N for (NH4)2SO4, but very large losses for KNO3. As in the experiments from 1974–1975, the experiments for 1975–1976 showed no 15N below 60 cm depth for KNO3, and below 30 cm depth for (NH4)2SO4. The percent of applied N which became immobilized range from 7 to 49%, with the highest value for (NH4)3SO4 on a Malmo sicl soil. In summary, substantial losses of late fall‐applied l5N‐labelled fertilizers occurred over the winter, with field experiments that were started in 2 different years. These losses from the soil averaged 67% for KNO3 (five experiments, range of 40 to 87%), 38% for urea (two experiments, range of 29 to 46%), and 10% for (NH4)2SO4 (five experiments, range of 1 to 18%). The overwinter loss of fall‐ or winterapplied N was not through leaching, but through denitrification which apparently took place in early spring. The amount of immobilization of the labelled fertilizers varied from experiment to experiment.