Summary. The uptake of iron (Fe) by VF-36 tomato plants as influenced by root temperature and manganese (Mn) nutrition was studied. Following a 1-week pretreatment period of various levels of Fe and Mn in the nutrient solution in a controlled temperatuire room, the uiptake of s9Fe from ferric ethylenediamine di(Ohydroxyphenylacetate) (FeEDDHA) Methods and MaterialsGeneral Procedures. Intact tomato plants were tused in these experiments. Seeds of VF-36 tomatoes were germinated on stainless steel mesh suspended over 9 liters of 10-4 M CaSO in plastic buckets. The seeds were covered and kept moist with a piece of filter paper, the corners of which dipped into the CaSO4 solution. The solution was aerated and the container was kept in the dark at 20°for 1 week, at which time the filter paper was removed and the entire mesh with the young seedlings was transferred to a dilute (1/10 strength) nutrient solution prepared from stock solutions of puirified macronutrients by methods described by Steinberg (20
Field experiments were conducted on organic soil for 3 years using relatively high rates of N to evaluate the influence of N on the growth and maturity of onions. In 2 years with low rainfall, maturity was not influenced, but yields declined with increasing rates of N. The decline in yield was originally attributed to ammonium toxicity, but observations with 3 sources of N indicated that high concn of fertilizer salts also could have caused injury to the plants. With high rainfall, yields increased with each increase in N, and as much as 240 lb. of N/acre was required for normal growth and maturation, while those onions receiving less than 120 lb. of N/acre were deficient in N and failed to mature properly. Utilizing different methods of incorporating N in the soil to evaluate the toxic response to N was unsuccessful in the wet season. Some indication of injury to the young seedlings occurred with the highest rates of N banded beneath the row, but these symptoms disappeared during subsequent periods of high rainfall.
Field experiments were conducted on organic soil for 2 years to evaluate the influence of frequent irrigation and topdressings with N on growth, maturity and storage life of onions (Allium cepa L.). With no irrigation, growth to midseason, maturity, and final yield were not influenced by increasing amounts of N. The growth to midseason, and the final yield increased and maturity was earlier with increasing amounts of N applied to onions receiving 5 cm of rainfall + irrigation per week. Sprouting in storage was earlier with high N and latest with no N or with the low N rates. The effect was greater with irrigation. Onions did not respond to N topdressing without irrigation even though rainfall was regular. With irrigation, the highest yield and earliest maturity was obtained with 22 or 34 kg of N/ha applied whenever the crop received 10 cm of water. No advantage in yield or maturity was obtained by applying N after mid-July. Maturity was earlier without irrigation regardless of N treatment.
Coincident with the world food shortage, ever-increasing food prices and the shortage and high and rising costs of energy, attention is now being directed to the energy-efficiency of agricultural production (1, 5, 6, 12, 13, 18, 30, 31, 34, 40, 45, 47, 48, 52). Although the energy used annually for agriculture in the United States (48) and Canada is not a large percentage of the national totals some feel that to ensure energy supplies “agriculture must stake a claim” (27). The “claim” must stress the form of energy because current agricultural technology is so dependent on liquid fuels for machinery operation and natural gas for the production of nitrogen fertilizers (40). As an important segment of the agricultural industry, horticulturists must also “stake a claim” to energy if they believe fruits and vegetables make a legitimate contribution to food supplies. Fruit and vegetable production is considered energy-extravagant because of the high energy inputs needed compared to the usable energy output (13, 47), although few studies of the energy relationships of individual horticultural crops have been reported. Presented herein are energy calculations for the production of some fruits and vegetables for which production data in Ontario are available with a discussion of the place of fruits and vegetables in a food supply system and the flaws inherent in judging production efficiency solely on an energy basis.
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