Efficient Fertilizing

These improvements range from such simple, relatively inexpensive, and widely available practices as repeated soil testing to the most sophisticated methods of vari- 

Correct placement of fertilizers is no less important. They should be put as close to the position of future, or existing, plant roots as is practical, but they should not 

A totally different approach to increasing the efficiency of fertilizing is to slow down the rate of nitrification, and hence to reduce the water-borne losses of the nutrient. This has been possible since the early 1960s when nitrapyrin, the first nitrification inhibitor, became commercially available. Many inhibitors are now on the market—nitrapyrin and dicyandiamide are the two most popular choices—but their use is rather expensive, their performance is highly variable, results from field tests are often contradictory, and their applications have been restricted to just a few field crops (above all corn and root crops) and special climatic conditions.  

Increasing efficiency of nitrogen fertilizer use in English wheat cultivation. 

Reducing erosion losses by about 20% would save roughly 5 Mt N from nonfertilizer sources, and expanding biofixation (largely through proper rotations with le- 

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An important prerequisite for successful application of the fruit fly male annihilation technique is an attractant compound or mixture powerful enough to reduce the male population to a level well below that required for efficient fertilization of the total egg mass. An appetite for the lure by the males after they are attracted to it is also essential for most effective application. With the overabundance of sperm production and mating capacity possessed by the oriental fruit fly, removal of from 50 to 80% of all males may be necessary before there will be an appreciable effect on egg hatch. Use of strong female lures in combination with the male elimination method would enhance effectiveness but, unfortunately, materials discovered thus far in intensive screening programs in Hawaii and Mexico have not possessed attractant qualities comparable to those of the male lures. 

Regardless of our achievements in more efficient fertilizing, during the next generation we should get a much clearer understanding of the real impact of this excess... 

The ammonia values can be recycled or sold for fertilizer use. The most important consideration ia this process is the efficient elimination of the phosphoms from the product, because as Htfle as 0.01% P2 5 electrolyte causes a 1—1.5% reduction ia current efficiency for aluminum production (28). 

Another area where improved air quaUty has impacted on sulfur use is ia agriculture. As sulfur dioxide emissions have decreased, sulfur content of soils has also decreased. Sulfur, recognized as the fourth most important plant nutrient, is necessary for the most efficient use of other nutrients and optimum plant growth. Because many soils are becoming sulfur-deficient, a demand for sulfur-containing fertilizers has been created. Farmers must therefore apply a nutrient that previously was freely available through atmospheric deposition and low grade fertilizers. 

Catalytic uses result in Htde consumption or loss of vanadium. The need to increase conversion efficiency for pollution control from sulfuric acid plants, which require more catalyst, and expanded fertilizer needs, which require more acid plants, were factors in the growth of vanadium catalyst requirements during the mid-1970s. Use was about evenly divided between initial charges to new plants and replacements or addition to existing plants. 

Fertile sources of carotenoids include carrots and leafy green vegetables such as spinach. Tomatoes contain significant amounts of the red carotenoid, lycopene. Although lycopene has no vitamin A activity, it is a particularly efficient antioxidant (see Antioxidants). Oxidation of carotenoids to biologically inactive xanthophyUs represents an important degradation pathway for these compounds (56). 

Agricultural Use. Citric acid and its ammonium salts are used to form soluble chelates of iron, copper, magnesium, manganese, and zinc micronutrients in Hquid fertilizers (97—103). Citric acid and citrate salts are used in animal feeds to form soluble, easily digestible chelates of essential metal nutrients, enhance feed flavor to increase food uptake, control gastric pH and improve feed efficiency. 

Table 2 Efficiency of use of nitrogen fertilizer by winter wheat, winter oilseed rape, potatoes and sugar beet.

Data of a different kind, the nitrate losses through the held drains of the Brimstone experiment,also suggest that winter oilseed rape uses nitrogen fertilizer somewhat less efficiently than does winter wheat, but this experiment did not include the other crops discussed above. 

After Flarvest. How do the memory effects shown by the other crops compare with those of winter wheat Winter wheat did not show a memory effect after one year, but oilseed rape does seem to do so. Researchers of the Agricultural Development and Advisory Service found that nitrate production by microbes in the soil after a rape crop increased with the amount of fertilizer given to the crop (R. Sylvester-Bradley, personal communication). One reason may lie in this crop s habit of shedding its leaves as harvest approaches, which means that the microbes in the soil get early access to these residues. This habit might contribute to the apparently smaller efficiency of this crop in using nitrogen fertilizer. The crop may be just as efficient as winter wheat at taking up the fertilizer but drops... 

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