IMPORTANCE OF FERTILIZER NITROGEN

Transcription

1 8 FLORIDA STATE HORTICULTURAL SOCIETY IMPORTANCE OF FERTILIZER NITROGEN FOR CABBAGE PRODUCTION ON SANDY SOILS IN NORTHEAST FLORIDA E. N. McCUBBIN Potato Laboratory Florida Agricultural Experiment Station Hastings Introduction Cabbage is one of the leading truck crops grown on sandy soil in northeast Florida during the fall, winter and spring. Bladen fine sand and Bladen fine sandy loam with reac tions generally ranging between ph.0 and 6.0 are the predominate types of soil used for growing the crop in this part of the State. They are low-lying soils underlaid with a heavy, sandy-clay subsoil that prevents rapid movement of water downward which is detri mental to drainage during rainy weather but an advantage for irrigation during droughty periods. Artesian water is available for irri gation and when the soils are properly drained, irrigated and fertilized they produce good yields of high quality cabbage. When the crop is grown in northeast Flor ida on sandy soils fertilized with ton of -7- commercial fertilized per acre, the plants sometimes develop an abnormal number of small leaves, become stunted, are light green to yellow in color and yield poorly. Such plants are most noticeable during cool weather and even occur in those fields which are ade quately drained and irrigated. Results of experiments conducted during the last years, as reported in this paper, show that poor yields of low-quality cabbage often are trace able to lack of a sufficient amount of nitrogen needed for the production of the crop. Methods The tests were conducted at Hastings, Flor ida, and consisted of () a single application of different fertilizers at the usual rate of ton per acre prior to setting the plants and () the addition of nitrogenous materials as side-dressings after the land had been fer tilized with ton of a -7- fertilizer and set to plants. Each treatment was replicated 8 or more times in -row plots. feet long, the rows being ridged 8 to inches high and spaced 0 inches apart. Early Copenhagen Market plants were set 9 inches apart in the rows in November and December and harvested in February, March and April. Fertilizers ap plied prior to transplanting were placed in a band in each side of the row to weeks before the plants were set. Those used for side-dressing were applied by hand on top of the plants or along each side of the plant row. The plots were irrigated when set to cabbage and as needed thereafter. Good drainage was provided to protect the field against flooding during heavy rains. Pounds of marketable cabbage produced in each plot were recorded and total yield for each treatment was con verted to tons per acre. Fertilizers Applied Before Transplanting The different fertilizer mixtures used, sourc es and amounts of nitrogen contained in the mixtures, numbers of years tested and aver age yields in tons per acre are given in table. Comparisons of the three -7- mixtures show that nitrogen in the nitrate form in creased the yield as special -7- mixture which supplied pounds of nitrate nitro gen to the acre outyielded commercial -7- mixture by. tons per acre. The latter fertilizer provided pounds of nitrogen but it was organic and ammonia nitrogen the first seasons with a little nitrate nitrogen added the last seasons. Mixture also out-

2 FLORIDA STATE HORTICULTURAL SOCIETY 9 yielded -7- mixture which supplied pounds of ammonia nitrogen. Special -7- fertilizer supplying 00 pounds of nitrate nitrogen produced the higest yield, 7.9 tons per acre. This yield, how ever, was only.8 and. tons per acre more than the yields from 0-7- mixtures and, respectively, both of which supplied 00 pounds mixture in table shows no improvement in yield by increasing the phosphorous (P O) from 7 percent to percent. Furthermore, there was little difference in the yield obtained from mixture 8 containing 0 percent potas sium (KO) and mixture containing per cent. The results of this test indicate that maximum yields of cabbage may be expected TABLE. Average Yields of Cabbage Produced During Years in Test Plots Fertilized with Mixtures Containing, 0 and Percent Nitrogen at the Rate of Ton or its Equivalent. No Treatment Fertilizer Commercial -7-* Special -7-*** Special -7- Special 0-7- Special 0-7-**** Special -7- Special -- Special -7-0 Source of Nitrogen 0% Peruvian Guano 0% Castor Pomace 0% Sulphate of Ammonia** Sulphate of Ammonia 0% 0%Nitrate of Potash Pounds Nitrogen Applied Number of Years Tested Tons Cabbage *PO, from acid phosphate; KO, 0% muriate of potash and 0% sulphate of potash. Potash magnesia added th and th years to provide 0 pounds of magnesium per ton. ** For th year N, % castor pomace and tankage, 60% sulphate of ammonia and 0% ni trate of soda. For th near N, % castor pomace and tankage, % sulphate of am monia. 0% uramon and 0% nitrate of soda. *** PO, from superphosphate; KO, muriate of potash. **** KO, from nitrate of potash. of nitrate nitrogen. These small increases in yield were not enough to offset the cost of the extra pounds of nitrogen. Yields obtained from plots fertilized with 0-7- mixtures were.0 to. tons per acre greater than the yield from those fertilized with -7- commercial fertilizer which con tained half as much nitrogen. Plants treated with the 0-7- mixtures were deep green in color during the cool part of the season and remained green until harvested; whereas those receiving the -7- commercial fertilizer were lighter green in color throughout the growing period. Comparison of -- mixture 7 with -7- from a 0-7- fertilizer supplying 00 pounds of nitrogen, 0 pounds of phosphoric acid and pounds of potash. Fertilizers Applied as Side-Dressing After Transplanting Tests were conducted for seasons (90- ) to determine the effect of nitrate of potash side-dressings on the yield of cabbage which was grown on soil that had been fertilized with a complete fertilizer prior to setting the plants. Some plots were fertilized with pounds of -7- commercial fertilizer per acre and others with pounds. After the plants were transplanted some plots in each group were not side-dressed, others were side-

3 0 FLORIDA STATE HORTICULTURAL SOCIETY dressed with nitrate of potash once, some twice and the remainder times. Each sidedressing consisted of an application of 60 pounds of nitrate of potash per acre which provided pounds of nitrate nitrogen at each application. The first treatment was made approximately 0 days after the plants were set, the second 0 days later and the third 60 days later. The data show that the nitrate of potash side-dressing increased the yields, each one causing an increase on plots that had been treated with -7- fertilizer at the -pound rate prior to setting the plants, table. Likeers for side-dressing cabbage in plots treated with pounds of -7- commercial fer tilizer per acre before the plants were set. During seasons 8 organic nitrogenous ma terials, ground dried blood, steamed bone meal, peanut meal, castor pomace, high grade tank age, milorganite, cotton seed meal and whale guano were compared with nitrate of soda. Each material was applied different times to supply pounds of nitrogen per acre at each application, the applications being made ap proximately 0, 0 and 80 days after the plants had been transplanted. Thus, total nitrogen used in growing the crop was 7 TABLE. Average Yields of Cabbage Produced During Years in Test Plots Fertilized with and Pounds of a -7- Commercial Fertilizer and Side-dressed 0 to Times with 60 Pounds of Nitrate of Potash. Treatment Pounds -7- Commercial Fertilizer Applie Before Transplanting* No. of Sidedressings** 0 0 Pounds Nitrogen Applied Tons Cabbage * Same fertilizer as treatment table. ** First treatment made 0 days after the plants were set, the second 0 days later and the third 60 days later. wise, plots which had been treated with -7- fertilizer at the -ton rate before the plants were set, produced a larger yield than those fertilized with pounds of the fertilizer and also a larger yield with each additional side-dressing. The yields were proportional to the amount of nitrogen applied per acre, the highest yield being obtained from 7 pounds of nitrogen which was the largest amount used. Plants given to side-dressings of ni trate of potash were darker green in color and produced larger heads which were crisper and of better quality than those treated only with -7- fertilizer. Additional tests were conducted to determine the value of various nitrogen-bearing fertilizpounds to the acre. During the years tested none of the materials bearing organic nitro gen produced yields that equalled those ob tained with nitrate of soda supplying nitrate nitrogen. Materials compared as side-dressing in other plots in 9 and in 9 were nitrate of potash, nitrate of soda, sulphate of ammonia, ammonium nitrate, uramon, N and P topdresser (containing nitrogen and pota&h), ammo-phos and -7- commercial fertilizer. For comparative purposes muriate of potash and a treatment without side-dressing were also included in this test. Enough muriate of potash was applied to provide pounds of potassium per acre at each application, while

4 FLORIDA STATE HORTICULTURAL SOCIETY the other materials were applied in amounts needed to supply pounds of nitrogen at each application. The materials were applied times in 9 or approximately 0, 0 and 80 days after the plants had been transplanted. In 9 they were applied only twice, and 67 days after the plants had been set in the field. Thus, total nitrogen applied per acre was 7 pounds the first season and pounds the second. The highest yields were obtained from sidedressings of nitrate of potash and nitrate of soda, both materials producing equally good yields and plants treated with them were deep green in color even in the cool part of the season. Ammonium nitrate and uramon pro duced the next highest yields-. The first of these materials supplied ammonia and nitrate nitrogen but it absorbed water readily and was difficult to apply after it had been stored a few weeks. Uramon provided water-soluable organic nitrogen and the yeilds obtained from it indicate that it could be substituted for nitrate of potash and nitrate of soda. Yields from muriate of potash were no better than from the no side-dressing treatment, indicating that the results obtained with nitrate of potash were due to nitrogen and not to potash. Conclusions Cabbage responded markedly to nitrate nitrogen and less so to other forms of this element. The -7- commercial fertilizer used at rates of pounds to pounds per acre supplied sufficient phosphorous- and potassium but not enough nitrogen for growing the crop. These tests showed that 7 to 00 pounds of nitrogen per acre are needed to pro duce maximum yields and that most of the nitrogen should be in the nitrate form for best results. The soil probably was too cold in December, January and February for the soil organisms to decompose nitrogenous materials and form nitrates for the crop. When the soil warmed up in the spring there was a deficiency of nitrates to supply the needs of a rapidly growing crop. Unfortunately nitrate nitrogen is soluable in water and may be lost easily in the drain age water of these sandy soils. However, since this form of nitrogen promoted maxi mum yields of cabbage, it appears necessary to use large quanities of it even though part may be lost by leaching. The disadvan tages of using nitrate nitrogen are partially offset by its lower cost in comparison to that of nitrogen from natural organic sources. These experiments suggest methods of fertilizing cabbage for production of maxi mum yields. One methods consists of an ap plication of a -7- commercial fertilizer at rates of to pounds per acre in the row a few days prior to seting the plants. Ad ditional nitrogen should be provided by to side-dressings of nitrate of potash or nitrate of soda. Each application should supply to pounds of nitrate nitrogen per acre. The first side-dressing should be made about weeks after the plants are transplanted and the others at to 0 day intervals, thereafter. Successful growers in the Hastings area use this method of fertilizing their crop. They may use nitrate of soda for the first sidedressings and nitrate of potash for the last application, or the latter material may be used for all applications. Few growers use nitrate of soda for all side-dressings because they believe cabbage treated with it just before harvest will become soft while in transit to market. The second method which does not require side-dressings, consists of an application of a special 0-7- fertilizer at rates of to pounds per acre before setting the plants in the field. This fertilizer should be placed in a band in each side of the row to weeks be fore the plants are set. The length of time between applying the fertilizer and setting the plants will depend on the amount of mois ture in the soil, the longer period being allowed if the soil is dry. This method eliminates time and labor to apply side-dressings* and it gives excellent yields of good quality cabbage. The methods of fertilizing cabbage were compared in 9 and they produced about the same yields, but the cost of the first method, including the labor to apply side-dressings, exceeded that of the second method by $6.00 an acre.

5 FLORIDA STATE HORTICULTURAL SOCIETY When no side-dressings were used, plots re ceiving ton of 0-7- fertilizer per acre yielded tons per acre more than those treated with ton of the -7- fertilizer. The highnitrogen mixture cost $0.0 more per ton than the -7- fertilizer, but the increase in yield from its use more than offset the cost of the additional nitrogen. A ton of the special 0-7- fertilizer may be made by mixing 70 pounds of nitrate of potash (% N. and % KO), 80 pounds of nitrate of soda (6%N) and 700 pounds of superphos phate (0% PO). This fertilizer has good drilling qualities when used to weeks after mixing, but it should not be stored from one season to the next because it absorbs water and becomes too wet to use in a fertilizer dis tributor. ORGANIC FUNGICIDES FOR CELERY G. R. TOWNSEND Everglades Experiment Station Florida Agricultural Experiment Station Belle Glade The development of organic fungicides has taken rapid strides since 90. As these new compounds have been offered by the fungicide manufacturers, the celery growers and Experi ment Station workers in Florida have had a keen interest in the possibilities of these com pounds as substitutes for copper fungicides on celery. There would be no merit in replacing copper fungicides if the copper compounds available met all the requirements of a good fungicide for celery, but unfortunately this is not so, and we have been helped in the realization of this by the performance of some of the new organic compounds. Bordeaux mixture of a --0 for mula applied at weekly intervals controls early and late blights of celery reasonably well, but ia known to retard the growth of the crop and leave an undesirable spray deposit. Changing the Bordeaux formula to --0 and adding two pounds of wettable sulphur improves the spray in respect to the visibility of the deposit, safety and fungicidal efficiency. The necessity of mixing several materials in the tank is often considered a handicap, and has given rise to the use of a number of insoluble copper com pounds such as basic copper chloride and cuprous oxide and tribasic copper sulphate. The basic copper chloride and cuprous oxide sprays are about as effective as Bordeaux spray of equal copper content, but they are liable to produce the same type of copper in jury and stunting as is found with Bordeaux mixture. The tribasic copper sulphate sprays is less effective as a fungicide, but not as likely to injure the foliage. With these characteristics of copper fungi cides in mind, we may proceed to discuss the new organic fungicides for celery. However, the discussion is intended only as a report of progress because the tests of organic fungi cides are continuing and new developments in their production may be expected for several years. Growers may safely use some of these materials on a trial basis, but they are cau tioned against a too rapid abondonment of the Bordeaux spray program for celery. Aside from the need for further testing, economic factors such as the cost and availability of the new compounds must be considered. Dithane (disodium ethylene bisdithio-carbamate) is available now as a clear amber colored liquid. It should be used at the rate of quarts to gallons of water. It is preferable to add also to each gallons of spray pound of ZnSO and / pound of hydrated lime. In