N.V. AND R. - ISSCT

1 74 AGRICULTURAL SECTION Mr. N. V. Mohan Rao presented the following paper. Paper SOME ASPECTS OF NITROGEN NUTRITION OF SUGARCANE IN ANDHRA MOHAN RAO and r . L. NARASIMHAM Sugarcane Research Station, Anakapalle, India. INTRODUCTION Sugarcane is one of the most important commercial crops in Andhra State and plays a vital role in the agricultural economy of the cultivator. It occupies an area of abopt 1,20,000 acres and shows indications of further increase ; over 80 percent of the area under cane is occupied by Co. 419. With eight sugar mills having a total crushing capacity of about 5,000 tons of sugarcane per day and producing over 40,000 tons of white sugar annually, the sugar industry has come to stay as the foremost in the State and stands fourth in the Indian Union.

2 While approximately 17 to 18 per cent of the cane grown goes to production of sugar, about 65 to 70 percent is converted into crude sugar made in the form of moulds, called Jaggery or Gur, which finds wide use for domestic consumption in place of &gar and is also exported to a considerable extent. Manuring is one of the most potent factors to step up yields of sugarcane and forms a major item in its cost of cultivation. Of the three major plant-food elements, sugarcane responds most to nitrogen in this State, no perceptible effects being observed in the case of potash and phosphoric acid . The total dose of nitrogen varies from about 100 lbs. per acre in the northern to about 200 ibs. in the southern and central districts.

3 Taking about 150 lbs. nitrogen per acre as the average for the State, the annual-requirement of nitrogenous fertilizer taken as ammonium sulphate works out to about 45,000 tons, involving an expenditure of approximately fifteen million rupees. The need for a scientific and rational schedule of fertilization in the interest of national economy is thus apparent. Studies were, therefore, directed to elucidate in detail the various biochemical aspects of nitrogen nutrition of sugarcane with particular reference to this tract; the effects of different doses, forms, and times of application of nitrogen on the qualitative and quantitative aspects of sugarcane production are discussed in the following pages. Preliminary studies conducted on the possibilities of the "foliar MOHAN RAO, R,L.

4 NARASIMHAM ~r~ty of the area. The alluvial delta soils of Godavari and Krishna are fertile ell-supplied in plant nutrients, showing some deficiency of nitrogen ; all sugarcane soils are more deficient in nitrogen and organic matter. The soils of the semi-arid inland districts are heavy clays, alkaline in reaction The climatic conditions of the State represent a transition from the sub- a1 Northern India to the hot and humid South ; the distribution of rainfall from about 40 to 45 inches in the northern districts to about 20 to 25 inches southern and central districts. The rainfall is received in two precise -December). Highest summer temperatures are recorded in the months -May, while the dry and chill winter usually lasts from December to The meteorological data for Anakapalle*, the main centre of sugarcane TABLE I December 64 1 Total for the year 59 *with a rainfall of inch and over, -- -- 76 AGRICULTURAL SECTION The soils of the Anakapalle tract are representative of the well-drained loams of the Northern districts ; analysis of the top one-foot soil is given in Table 11.

5 TABLE I1 PH Mechanical analysis : Total nitrogen Moisture Organic carbon Clay Lime Silt Available PzOs Coarse and fine sand Exch. calcium m. eq. per 100 gm. Water soluble salts Sugarcane is normally planted in the months February-April, and harvested after a year ; after completion of germination and tillering, active growth commeiices from June and extends till December, coinciding broadly with the mci:lsoons, after which maturity sets in. REVIEW OF LITERATURE The role of nitrogen fertilization in the production of sugarcane has received probably the greatest attention in agronomic research on the crop. Earlier work by Das (ll), and Das and Cornelison (12) showed that higher nitrogen doses increased elongation, tillering, leaf-width, and succulence of the plant ; while the sucrose per cent in juice was depressed, the glucose, alcohol soluble as well as total nitrogen and the mineral matter in the same showed an increase.

6 Ayres (4) reported that sugarcane absorbed potash and silicon to a much greater degree than nitrogen and phosphorus and this absorption was governed by the stage of developnlent of the plant ; he also found that the highest concentratioil of these elements in the dry matter of the plant occurred at three months age and that, while the rate of absorption of nitrogen diminished after reaching a maximum by about six months, that of' calcium, magnesium, phosphorus and potash continued to increase till a far later age. Kobus (21) reported from Java that nitrogen absorption was most rapid under those conditions upto 8 months of age, followed by a decrease. ~ordeh (6,7,8,9,10) elaborated the studies on nitrogen nutrition of sugarcane in Hawaii; he stated that ilitrogen increased the same in all parts of the plant, particularly the foliar tissues and the nitrogen content declined with age.

7 The total green and dry weight of the plants and also the green tops generally increased with higher nitrogen application, the effect of the initial increments of nitrogen being more marked. Nitrogen also depressed arrowing and tended to promote lodging in cane. Borden (5) also reported oil the role of climatic conditions, particularly light and temperature, on nitrogenutilisation, stating that deficiency of the same retarded growth. The results from fertilizer experiments conducted in the Dominican Republic and South Africa were recently reviewed by Aughtry et a1 (3), and Du Toit (14); Innes (19) dealt .with the inorganic MOHAN RAO, NARASIMHAM 77' from nitrogen in all the cane-tracts, while potash and phosphoric acid under nitrogen deficiency and that the optimum uptalte of nitrogen, scussed by Lakshrnikantam (22), who reported that they did not come to the eve1 of concentrates in respect of nitrogen nutrition ; similar observations were also made by Rege (32).

8 Parthasasathy and Lakshmiltaniam (30) reviewed. the fertilizer experiments with nitrogenous manures on sugarcane in Madras and observed that under low soil moisture conditions, organic ilitrogenous manures were better suited, while ammoniunl sulphate was effective under a comparatively more plentiful water supply. EXPERIMENTAL DETAILS Detailed investigations on the influence of graded doses of nitrogen on the uptake of the same by the cane plant, dry'matter production and the ultimate yield of cane and sugar were conducted in a field experiment during the years 1948-49 to 1950-51. The layout was one of split-plot design, with two varieties, Plant samples (above-ground portion) were drawn by the Unit Length AGRICULTURAL SECTION + the effects of the treatments on the soil fertility, alialysis of the same was conducted before and after harvest of the crop, adopting the usual ailalytical methods.

9 (1,31). Detailed juice analysis for the sugar and noa-sugar constituents was conducted on composite samples for the respective treatments, following the procedures given by (I), Fort and McKaig (16), Kharin and Srniriiova (20), and Spencer and Meade (38): The data collected are presented and discussed hereunder. RESULTS AND DISCUSSION INFLUENCE OF NITROGEN ON CROP PERFORMANCE (i) Uptake of nitrogen by the crop:-The data for the nitrogen content of the plant (varieties Co. 527 and Co. 419), as influenced by the different doses of nitrogen are presented in Table 111. TABLE 111 NITROGEN-CONTENT OF STEM AND WHOLE-PLANT (% DRY MATTER) (March-plantyd crop) Treatments* June July Aug. Sept. Nov. Jan. March : 100N S - 0'65 0'52 0'32 0'34 - P do 150N S - P do 200 N S - - P CO.

10 419: 100N S - - P do 150N S - - P ' do 200N S - - P *S : Stems alone ; P : Whole plant. The nitrogen-content of the stem tended to show a slight increase upto August, especially in the higher nitrogen doses, and later followed the same trend as whole-plant. The nitrogen concentration in the plant was highest in the early stages, the youngest plant having the maximum nitrogen percent dry matter. There was a fall in the nitrogen concentration with age, under all conditions, that at the "boom stage" being most rapid, indicating the rapid utilisatioil by the growing crop at this stage (Fig. I). The necessity for maintaining high concentratioil of nitrogen in the plant in the early stages of growth has often been 80 AGRICULTURAL SECTION In spite of the higher nitrogen concentration in the plant, the actual uptake per acre in the early formative stage was the lowest; the nitrogen uptake rapidly increased with the onset of the grand-period of growth (from June), and by about six months age it was found that a inajor portion of the total uptake was completed (Fig.)