NITROGEN FERTILIZATION OF SUGARCANE ON A SANDY SOIL: I. YIELD AND LEAF NUTRIENT COMPOSITION

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1 NITROGEN FERTILIZATION OF SUGARCANE ON A SANDY SOIL: I. YIELD AND LEAF NUTRIENT COMPOSITION R. M. Muchovej and P. R. Newman Southwest Florida Research and Education Center, University of Florida, Institute of Food and Agricultural Science, 2686 State Road 29 North, Immokalee, FL ABSTRACT The determination of optimum N fertilization rates for sugarcane (Saccharum spp. hybrids) on Florida sandy soils has been limited to a few studies. The objective of this study, conducted during at the Southwest Florida Research and Education Center, UF-IFAS, at Immokalee, FL (27 25' N, 81 25' W), was to determine the response of sugarcane cultivar CP grown on a sandy soil to varying N rates. Three rates of N fertilizer (170, 280, and 390 kg N ha -1 yr -1 ) were evaluated. The N fertilizer rates were surface applied next to the row in four split applications at 8-wk intervals between March and September. Sugarcane leaf samples were collected for nutrient analysis from each plot, between May and October. Samples were taken 4.5 and 4.0 wk following the latter three split applications of fertilizer in the first ratoon and second ratoon crops, respectively. Nitrogen concentration was obtained in Kjeldahl digests. Phosphorus, K, Ca, Mg, Zn, Mn, Cu, Fe, B, and Na were determined by ashing ground samples, dissolving the ash in HCl and filtering. Concentrations of elements in the filtrate were determined at the Analytical Research Laboratory (ARL), UF-IFAS, at Gainesville, FL, by inductively coupled plasma (ICP) or atomic absorption spectrophotometry (AAS) in combination with colorimetric analysis for P. Leaf macro and micronutrient concentrations were not affected by the N rates. Sugarcane and sugar yields also were not affected by N fertilizer rates greater than 170 kg N ha -1 yr -1. Only stalk weight in the second ratoon crop approached a significant slope for N rate (g stalk -1 = 0.51 kg N ha -1 yr ; r 2 = 0.25, P = 0.096). INTRODUCTION Twenty percent of the 2001 Florida sugarcane crop was grown on sandy soils (40,500 ha) (Glaz and Gilbert, 2003). Unlike the Florida muck soils (Histosols), these soils required N fertilization for acceptable sugarcane production. Soil water in these production areas is controlled by a combination of pre-plant laser leveling and maintaining a soil water table at 61 cm during the dry season and 76 cm during the rainy season (Lang et al., 2002). During 1996 through 2003, the south Florida rainy season was June-September, averaging 200 mm of rainfall for each month (FAWN, 2004). Monthly rainfall during October-May averaged 32 to 112 mm. Total yearly rainfall averaged 1296 mm (FAWN, 2004). Nitrogen Dynamics Nitrification, the release of organic N to plant available forms (R-NH 4 NH + 4 NO3 - ), is favored by high concentrations of NH + 4 in the soil, sufficient populations of nitrifying organisms, ph ranging from 5.5 to 10.0, aerated and dry to moist soil conditions, and temperatures above 3 o C (Tisdale and Nelson, 1975). Conditions for nitrification are met most of the time in Florida sandy soils where sugarcane is grown except where the soil ph is below

2 Journal American Society Sugar Cane Technologists, Vol. 24, 2004 and after heavy rains when the soil becomes water-saturated causing anaerobic conditions. Retention of soil NH 4 + may be limited due to low cation exchange capacity and low organic matter allowing movement of the cation with soil water. Soil NO 3 - is free to move with soil water because of its anionic charge. Soil water movement may be upward during warm dry sunny weather or downward during rainfall events. Denitrification (NO 3 - N gas) is likely to occur, since these soils generally have a high water table with a spodic horizon. Evidence of denitrification was documented in Florida Spodosols by Crandall (2000) beneath citrus groves on sandy soils with a shallow water table (1.5 m). Nitrogen Fertilizer Rates World recommended rates of N fertilizer for sugarcane production vary between 45 and 300 kg N ha -1 yr -1 (Srivastava and Suarez, 1992). The response to N fertilization occurs more in ratoon crops than on plant-cane crops (de Geus, 1973; Wood, 1964). The optimum rate of N fertilizer for sugarcane in many areas is between 100 and 200 kg N ha -1 yr -1 (de Geus, 1973). For many locations, the depletion of plant-available soil N over time justified the need for split application of the yearly total N rate. This was demonstrated by Wiedenfeld (1997) by a negative soil NO 3 -N concentration response to the time interval between N fertilizer application and soil sampling. In Louisiana, recommended N rates for plant-cane crops are 90 to 135 kg ha -1 for most areas except for the Red River Valley where recommended N rates are 135 to 157 kg ha -1 (Curtis and Loupe, 1975). Ratoon crop N recommendations are 135 to 157 kg N ha -1 yr -1 for all areas (Curtis and Loupe, 1975). When these recommended rates equal 135 kg N ha -1 yr -1 or more, two-thirds of the total rate should be applied in April or early May followed by the remaining fertilizer in June (Curtis and Loupe, 1975). A review of south Texas sugarcane nutrient studies by Rozeff (1990) recommended 56 and 90 kg N ha -1 for the plant-cane crop following a fallow rotation and for the successive crop rotation, respectively. Ratoon crop recommendations were 100 to 157, 134 to 190, and 168 to 202 kg N ha -1 for the first, second, and third crops, respectively. In South Africa, the optimum N rate for the first ratoon crop was different among the cultivars tested (0 to 100 kg N ha -1 ) and incrementally greater at each successive ratoon crop (50 to 150 kg N ha -1 yr -1 ) (Inman-Bamber, 1984). The plant-cane crop did not respond to any of the rates tested in the pre mentioned South African study, and this lack of response was attributed to the study being conducted on a virgin soil. In most areas of Australia, current recommended rates for N fertilizer are 120 to 150 kg N ha -1 for the plant-cane crop following a fallow period and 160 to 200 kg N ha -1 for successive plant-cane crop and ratoon crops (Canegrowers, 2002). Recommended rates were lower in areas of annual rainfall with less than 1200 mm and areas that have alluvial or peat soil (Canegrowers, 2002). Higher rates were recommended for the Burdekin and Mareeba districts, largely due to better growing conditions such as higher soil fertility and higher rainfall (Canegrowers, 2002). 211

3 Muchovej: Nitrogen Fertilization of Sugarcane on a Sandy Soil: I. Yield and Leaf Nutrient Composition The establishment of optimum N fertilization rates for Florida sandy soils has been limited to a few studies. Gascho (1983) determined that the highest sugarcane yields were obtained at N rates of 224 and 448 kg ha -1 for plant-cane and first ratoon crops, respectively, with the use of slow-release nitrogen applied in four split applications on a complex of Pompano and Leon fine sand at Delray, Florida. Gascho (1983) also reported that the cultivars tested had different N use efficiencies. Sugarcane yield of cultivar CP on a Basinger sand was greater with more split applications (five splits for plant-cane and four splits for ratoon) than less split applications (three splits for plant-cane and two splits for ratoon) at the same rate of N fertilization (224 kg N ha -1 yr -1 ) (Obreza et al., 1998). However, in the second ratoon crop, the difference between numbers of split applications was not conclusive. The current recommended N rate for Florida sugarcane is 90 kg ha -1 yr -1, but the rate was derived from research for sugarcane syrup production (Kidder et al., 2002). According to Rice et al. (2002), the nutritional requirement of sugarcane grown on sandy, mucky-sand, and sandy-muck soils appears to be 202, 123, and 34 kg N ha -1 yr -1, respectively, by split applications during the growing season. The objective of this study was to determine the effect of varying N rates on the yield and leaf nutrient concentrations of a major sugarcane cultivar (CP ) grown on a sandy soil in south Florida. MATERIALS AND METHODS The study was conducted during 1999 through 2003 at the Southwest Florida Research and Education Center, UF/IFAS, at Immokalee, FL (27 25' N, 81 25' W). The soil at this 1.6 ha study site was classified as Malabar fine sand (Grossarenic Ochraqualf), 98 % sand (< 2 % organic matter) with an argillic horizon at 1 m (Pitts et al., 1991). The site was surrounded by a 1.5 m deep rim ditch for surface and groundwater control. The ditch also supplied the water for seepage irrigation. Prior to the initiation of the experiment, the area was not planted for nine years. In 1999, weeds were controlled prior to planting in the plots by use of 1.0 kg a.i. ha -1 glyphosate [N- (phosphonomethyl) glycine isopropylamine salt], 0.9 kg a.i. ha -1 paraquat dichloride [(1,1 -dimethyl-4, 4 -bipyridium dichloride)], and mowing. The twelve ha plots were rotor-tilled to a depth of 10 to 15 cm before planting. All plots were planted with sugarcane cultivar CP at 1.5 m row spacing on December 9-13, The initial fertilizer mix that included 67, 22, and 67 kg ha -1 of N, P 2 O 5, and K 2 O, respectively, was applied in the 18 cm deep planting furrow in all plots. Wireworm damage was prevented by applying 3.8 kg a.i. ha -1 phorate {0,0-diethyl s- [(ethylthio) methyl] phosphorodithioate} in the planting furrows. The plot size was nine rows x 24.4 m (329 m 2 ) for the plant-cane crop then reduced in size to seven rows x 15.2 m (160 m 2 ) for the ratoon crops. After planting, piezometers (1.5 m x 7 cm diameter polyvinyl chloride pipes with fine slits in the lower two-thirds and wrapped with plastic screen cloth) were installed in the center of each plot to a soil depth of 1.3 m. The water table was recorded from the piezometers at biweekly intervals in the ratoon crops only. Water-table depth was measured by recording the vertical distance between the soil surface and the surface of the groundwater in the piezometers. Rainfall and temperature data were recorded by a weather station operated by FAWN (2004), located less than 1 km from the study site. 212

4 Journal American Society Sugar Cane Technologists, Vol. 24, 2004 Seepage irrigation water was supplied from a nearby deep well and a series of underground pipes between the plots that allowed transfer of irrigation water to plot perimeter ditches. Irrigation and drainage was provided to target a water-table depth between 46 and 76 cm from the soil surface. The experimental design was a randomized complete block design with three N fertilizer treatments and four replications. The blocking gradient was from east to west due to the irrigation pattern across the experimental area. The treatments were 170, 280, and 390 kg N ha -1 yr -1 split into four applications each. In the plant-cane crop, the splits were divided between the December planting, and three other dates separated by 8 to 11 wk starting in April. For the first and second ratoon crops, the splits were started in March and then separated by 8 wk intervals. Each plot received the same treatments in each of the three years of the study. The fertilizer was placed on the soil surface next to the planted rows within the plots. Phosphorus and K were included in the split application fertilizer mixes but at the same rate for all plots. Table 1 summarizes the fertilizer rates and timing. During the study period, weeds were controlled on an as-needed basis. Two applications of 1.2 kg a.i. ha -1 dimethylamine salt of 2,4-dichlorophenoxyacetic acid and 0.4 kg a.i. ha -1 dimethylamine salt of dicamba (3,6-dichloro-o-anisic acid) were made on 5 April 2000 and 20 March Tillage was limited to the plant-cane crop by the use of a roto-tiller between the rows on 20 April Weeds were suppressed in the second ratoon crop with a trash blank from the first ratoon crop. There was no pre-harvest burning for each crop. The crops were cut from the crown by hand in mid-january and removed by a front-end-loader for the plant-cane crop and by hand for the first and second ratoon crops. Each cropping cycle was 12 to 13 months. Most of the sugarcane trash was removed after the plant-cane crop, but no trash was removed after the first ratoon crop. The trash blanket was not incorporated into the soil. Yield Estimation The number of mature stalks ha -1 for each plot was estimated in October or November by counting the number of mature stalks in the two center rows of each plot. Mature stalk counting excluded any stalks that had a terminal leaf whorl below the majority of the leaf canopy, which was considered to die out before the normal harvest period. Two 10-stalk samples were taken from each plot at two dates in the ratoon crops, November and January, and only in January for the plant-cane crop. The sugarcane sample included randomly selected mature stalks within the center two rows of the plot, which excluded the tops, green leaves, and senesced brown leaves. Each stalk was toped at the apical meristem and cut at the base just above the soil surface. The average mature stalk weight for each plot was estimated by dividing the total sugarcane sample weight by the number of stalks in the sample. The estimated sugarcane yield (Mg ha -1 ) was calculated for each plot from the estimated plot stalk number and the estimated plot stalk weight. The sugarcane stalk samples were crushed in a three-roller mill at the Everglades Research and Education Center, UF-IFAS, at Belle Glade, FL 1 day after the samples were taken from the field. The sugarcane samples for juice analysis were reduced to two, five-stalk samples per plot. The extracted juice was analyzed for the proportion of total solids (Brix, %) and sucrose (polarity, %) using a refractometer and saccharimeter, respectively. The juice was 213

5 Muchovej: Nitrogen Fertilization of Sugarcane on a Sandy Soil: I. Yield and Leaf Nutrient Composition clarified with ABC Sugar Clarifier (Baddley Chemicals Inc., Baton Rouge, LA) and filtered before the saccharimeter measurement. Percent juice sucrose was calculated from Brix, polarity, and temperature values by the following modified formula from Korndërfer et al. (1995). Corrected Brix, % = [(Temp. C - 20) x 0.058] + uncorrected Brix, % [1] Juice sucrose, % = (Polarity, % x 26)/{ (corrected Brix, % - 15) x 0.444} [2] Sucrose concentration (kg Mg -1 ), which estimates the raw sucrose yield of sugarcane from the milling process, was estimated by the following modified formula from Korndërfer et al. (1995). The cultivar correction factor for all calculations was 1.0. Sucrose concentration = [(Juice sucrose, % x ) - (corrected Brix, % x 3.075)] x cultivar correction factor [3] The estimated sugar yield (Mg ha -1 ) was calculated for each plot as the product of sugarcane yield and sugarcane sucrose concentration. A cultivar fiber factor and a mill factor were not included in the calculations for sugar yield. Leaf Sampling Sugarcane leaf samples were collected between May and October for nutrient analysis. Samples were taken at 4.5 and 4.0 wk following the latter three-split applications of fertilizer in the first ratoon and second ratoon crops, respectively. Sugarcane leaf samples consisted of the youngest fully emerged leaf (laminae with midvein) collected from 10 randomly selected mature stalks from each plot. Leaves were sampled at hr. The 10 leaves were placed in labeled paper bags, dried in a forced air oven at 60 o C for 72 hr, ground, and passed through a 10 mm stainless steel screen. Nitrogen concentration was obtained by digesting 0.10 g of the ground tissue with 2.5 ml 18.0 M H 2 SO 4 and 1.0 g Kjeldahl digestion mixture (10 g K 2 SO g CuSO 4 ) for 2.5 to 3.0 hr followed by 500-fold H 2 0 dilution. Semi-automated colorimetric analysis was used to determine N in filter digestates by the Analytical Research Laboratory (ARL), UF-IFAS, at Gainesville, FL. Phosphorus, K, Ca, Mg, Zn, Mn, Cu, Fe, B, and Na were determined by ashing 1.5 g of the ground sample at 500 C for 5 hr. The ash was dissolved in 15 ml 6.0 M HCl and filtered. Concentrations of elements in the filtrate were determined at the ARL using inductively coupled plasma (ICP) or atomic absorption spectrophotometry (AAS) in combination with colorimetric analysis for P. Laboratory blanks were included in both digestion procedures to identify possible contamination. Statistical Analysis Sugarcane yields and leaf analysis data were analyzed as a split-split-plot treatment arrangement within a randomized complete block design (RCBD). The study was treated as a repeated-measures experiment with the three N-fertilizer rates as the main plots, the sample date 214

6 Journal American Society Sugar Cane Technologists, Vol. 24, 2004 as the sub-plot, and crop as the sub-sub-plot. Only significant parameters for the N-fertilizer main effect were regressed over increasing N-fertilizer rates. RESULTS AND DISCUSSION The total rainfall from January to December was 1074, 1603, and 1180 mm for the plantcane, first ratoon, and second ratoon crops, respectively. The majority (60-70 %) of the total yearly rainfall occurred during the second part of the growing season, July to October, for the plant-cane and first ratoon crops, whereas only 41 % occurred during the same period for the second ratoon crop. Temperatures at or below 0 C were recorded only in the month of January during the plant-cane and second ratoon crops and only once in the month of December during the plant-cane crop. The water-table depths ranged from 30.9 to 90.6 cm below the soil surface in the first ratoon crop and from 50.4 to 96.0 cm in the second ratoon crop during the March to October growing season (Figure 1). In late August 2002, during the second ratoon crop, the water table reached the soil surface because of an irrigation pump malfunction. Sugarcane Production The only significant yield measurement for the N rate main effect was stalk weight (P<0.05) (Table 2). Stalk weight was not significant for any of the interactions between N rate, harvest date (sample time), or crop. The harvest main effect was not significant for stalk weight (P>0.05), while the crop main effect was highly significant (P<0.01). Stalk weight in the plant-cane and first ratoon crops was not significantly affected by N fertilizer rate. However, the second ratoon crop stalk weight increased slightly with increasing N rate (g stalk -1 = 0.51 kg N ha -1 yr ; R 2 = 0.25, P=0.0962). Cane and sugar yields did not respond to N fertilizer rate at any harvest dates in any crop (P>0.10) (Table 3). However, there was a numeric increase in sugar yield with increasing N rates at each recorded harvest in all crops. The lack of response to N fertilizer rates used in this study indicates that even the lowest rate tested (170 kg N ha -1 ) may have been at or above the critical N rate for sugarcane production on sandy Florida soils. The current University of Florida N fertilizer recommendation for sugarcane grown on these soils is 202 kg N ha -1 yr -1 (Rice et al. 2002). The lack of yield response to N fertilizer in this study (Table 3) may also be related to the proportion of N fertilizer used at each split application. Borden (1948) indicated that sugarcane production was greater if the last N application was completed by the fourth or sixth month on a 12 or 18 month crop. In addition, Samuels (1969b, p ) reported that sugarcane N requirements were greatest in the early stages of growth, germination and boomstage growth periods. In this study, the fertilizer was applied in four splits each year with the last split application occurring after the 6th month. The proportion of the total N fertilizer at each split application varied for each N fertilizer treatment. The difference between the N fertilizer rates applied was 0 kg N ha -1 in the first split. For the second split in April-May, there was a 44 and 215

7 Muchovej: Nitrogen Fertilization of Sugarcane on a Sandy Soil: I. Yield and Leaf Nutrient Composition 34 kg N ha -1 difference in rate between the low and medium rates and the medium and high rates, respectively (Table 1). The same differences in N fertilizer rates were made at the third split in June-July (Table 1). For the fourth split in August-September there was a 22 and 44 kg N ha -1 difference in N fertilizer rate between the low and medium rates and the medium and high rates, respectively (Table 1). The numerical difference between the three N rates became distinctive by the time of the August-September split application. Nevertheless, it is unclear from this study whether the sugarcane plant will respond to varying N rates better in the spring or midsummer or late summer on south Florida sandy soils. In this study, the relative sugar yields between crops were atypical of fallow-plant sugarcane production on sandy soils. First ratoon crop yield was 126 % of the plant-cane crop, and the second ratoon crop was 74 % of the plant-cane crop. Generally, sugarcane production planted on fallow land results in higher sugar yields for the plant-cane crop with declining sugar yields in the successive ratoon crops (Glaz and Ulloa, 1995). The relatively lower sugar production for the plant-cane crop is most probably due to the time of planting. Normally, fallow plant fields are established from August to October, whereas this study had a December planting. Therefore, higher sugar yields for the first ratoon crop when compared with the plantcane crop as observed in this study would not be unusual. However, the 41 % decline in sugar yield from the first ratoon crop to the second ratoon crop was exceptional. The drop in sugarcane production of successive ratoon crops has been attributed to a decrease in soil N (de Geus, 1973; Wood, 1964). In this study, the dramatic decline in sugar yield was likely related to the trash blanket from the first ratoon crop that tied up N from use by the successive crop. Based on results from soil and groundwater analyses, Muchovej and Newman (2004) inferred that N was indeed immobilized by soil microorganisms trying to break down the organic matter in the trash blanket for much of the second ratoon crop growing season. Leaf N Leaf N concentrations at 4 wks following the second, third, and fourth split N-fertilizer applications did not differ between N rates except for the 280 and 390 kg N ha -1 rates on October 4 during the second-ratoon crop (P=0.0561) (Table 4). Most of the leaf N concentrations were below the critical value of 11.0 g N kg -1 established by Samuels (1969a) for sugarcane leaf lamina samples with the midvein. The low leaf N concentrations may have resulted from the timing of the sampling, which was 4 wk following the split applications. In this time interval, rapid sugarcane growth and dry matter accumulation may have occurred, contributing to N dilution in the leaves. Jarrell and Beverly (1981) have described this nutrient dilution effect for a number of plant species, including many grasses. Leaf macro- and micro-nutrients were not affected by N rate when sampled at 4.0 to 4.5 wk following the latter three split applications of fertilizer in the first and second ratoon crops (P>0.05). There were only three significant N-rate x crop interactions (P<0.05). Across sampling time, first-ratoon crop leaf K concentrations were 9.1, 10.0, and 9.0 g kg -1 for 170, 280, and 390 kg N ha -1, respectively, whereas second-ratoon crop leaf K concentrations were 10.3, 8.6, and 8.4 g kg -1 for the respective N rates. Also, across sampling time, first ratoon crop leaf Cu concentrations were 3.4, 4.6, and 4.0 mg kg -1 for 170, 280, and 390 kg N ha -1, respectively, whereas second-ratoon crop leaf Cu concentrations were 5.4, 4.5, and 4.3 mg kg -1 for the same N 216

8 Journal American Society Sugar Cane Technologists, Vol. 24, 2004 rates. Within the 4 wk post third split application of fertilizer sampling, first ratoon crop leaf Fe concentrations were 45.3, 46.5, and 44.0 mg kg -1 for 170, 280, and 390 kg N ha -1, respectively, and 41.4, 43.7, and 49.3 mg kg -1 in the second ratoon crop for the respective N rates. The sampling time and crop effects for leaf macro- and micro-nutrient concentrations were significant (P<0.05) (Table 5). Leaf nutrient concentrations fluctuated across sampling time within crop and differed among crops at similar sampling dates. Leaf K concentrations increased with time during the first ratoon crop but decreased with time in the second ratoon crop. Leaf B and Na concentrations increased with time in the second ratoon crop, while in the first ratoon crop, they were not different or fluctuated with time. These different patterns in leaf nutrient concentrations between first and second ratoon crops may be due to differences between the presence and absence of a trash blanket, as well as rainfall and climatic conditions. CONCLUSIONS Nitrogen fertilizer rates greater than 170 kg N ha -1 yr -1 did not increase sugarcane yield when the fertilizer was surface applied next to the rows in four splits (March-September at 8 wk intervals). Overall, leaf macro- and micro-nutrient concentrations were not affected by the N rates tested. ACKNOWLEGEMENTS This research was supported by the Florida Agricultural Experiment Station and approved for publication as Journal Series No. R We thank John Perry of Moore Haven Florida who supplied the sugarcane seed-cane for this study. In addition, we recognize Matt Dutchrow and Robert Taylor of the Sugar Cane Growers Cooperative of Florida for assisting in the milling of the sampled sugarcane for juice analysis and Jeff Jones, Ann Summeralls, Rudy Aragus, and Michael Obern for technical assistance. The authors are also thankful to Dr. Thomas Obreza, Univ. of Florida/Soil and Water Science Dept., for comments and review of the manuscript. DISCLAIMER The product names and trademarks are mentioned only to report factually on available data. The University of Florida does not guarantee or supply warranty to the use of these products and does not imply the exclusion of other products that may be suitable. 217

9 Muchovej: Nitrogen Fertilization of Sugarcane on a Sandy Soil: I. Yield and Leaf Nutrient Composition REFERENCES 1. Borden, R.J Nitrogen effects upon yield and composition of sugarcane. Hawaiian Planter s Rec. 52: Canegrowers Code of Practice for Sustainable Cane Growing in Queensland. [Online] Canegrowers, Brisbane, Queensland, Australia. 27 pp. 3. Crandall, C.A Distribution, movement, and fate of nitrate in the superficial aquifer beneath citrus groves, Indian River, Martin, and St. Lucie Counties, Florida. [Online] Water-Resources Invest. Rept U.S. Geol. Surv. 4 Curtis, O.D., and D.T. Loupe Fertilizer and soil fertility practices for sugarcane production in Louisiana. Sugar Bull. 53(10): de Geus, J.G Sugar crops. Pages: In: Fertilizer Guide For The Tropics And Subtropics. 2 nd ed., J.G. de Geus, ed. Centre D'Ẽtude de L'Azote, Zurick. 6. FAWN Immokalee monthly rainfall data. [Online] Florida Agricultural Weather Network, Univ. of Fla., Gainesville. 7. Gascho, G.J The effect of nitrogen rate on four sugar cane varieties grown on sand. J. Amer. Soc. Sugar Cane Technol. 2: Glaz, B., and R.A. Gilbert Sugarcane variety census: Florida [Online] Fla. Coop. Ext. Ser. Doc. SS ARG 198. Univ. of Fla., Inst. Food Agric. Sci., Gainesville. 9. Glaz, B., and M.F. Ulloa Fallow and successive planting effects on sugarcane yields in Florida. J. Amer. Soc. Sugar Cane Technol. 15: Inman-Bamber, N.G The effects of nitrogenous fertilizer on sugarcane varieties and varietal differences in third leaf nutrient content. Proc. Ann. Congr. S. Afr. Sugar Technol. Assoc. 58: Jarrell, W.M., and R.B. Beverly The dilution effect in plant nutrition studies. Adv. Agron. 34: Kidder, G., C.G. Chambliss, and R. Mylavarapu UF/IFAS Standardized Fertilization Recommendations for Agronomic Crops. [Online] Florida Coop. Ext. Ser., UF/IFAS, Doc. SL-129. Univ. of Fla., Inst. Food Agric. Sci., Gainesville. 13. Korndörfer, G.H., D.L. Anderson, K.M. Portier, and E.A. Hanlon Phosphorus soil test correlation to sugarcane grown on Histosols in the Everglades. Soil Sci. Soc. Am. J. 59:

10 Journal American Society Sugar Cane Technologists, Vol. 24, Lang, T.A., S.H. Daroub, and R.S. Lentini Water management for Florida sugarcane production. [Online] Fla. Coop. Ext. Ser. Doc. SS ARG 231. [11 p.] Univ. of Fla., Inst. Food Agric. Sci., Gainesville. 15. Muchovej, R.M., and P.R. Newman Nitrogen fertilization of sugarcane on a sandy soil: II. Soil and groundwater analyses. J. Amer. Soc. Sugar Cane Technol. 24: Obreza, T.A., D.L. Anderson, and D.J. Pitts Water and nitrogen management of sugarcane on sandy, high water-table soil. Soil Sci. Soc. Am. J. 62: Pitts, D.J., D.L. Myhre, Y.J. Tsai, and S.F. Shih Effect of water-table depth on water relations and yield for sugarcane grown on sand. J. Amer. Soc. Sugar Cane Technol. 11: Rice, R.W., R.A. Gilbert, and R.S. Lentini Nutritional Requirements for Florida Sugarcane. [Online] Florida Coop. Ext. Ser., UF/IFAS, Doc. SS-ARG-228. Univ. of Fla., Inst. Food Agric. Sci., Gainesville. 19. Rozeff, N A survey of south Texas sugarcane nutrient studies and current fertilizer recommendations derived from this survey. J. Amer. Soc. Sugar Cane Technol. 10: Samuels, G. 1969a. Method of foliar diagnosis. Pages: In: Foliar Diagnosis of Sugarcane, G. Samuels, ed. Adams Press, Chicago. 21. Samuels, G. 1969b. Major element nutrition with respect to foliar diagnosis. Pages: In: Foliar Diagnosis of Sugarcane, G. Samuels, ed. Adams Press, Chicago. 22. Srivastava, S.C., and N.R. Suarez Sugarcane. [Online] Pages: In: World Fertilizer Use Manual, W. Wichmann, ed. BASF AG, Germany. 23. Tisdale, S.L., and W.L. Nelson Soil and fertilizer nitrogen. Pages: In: Soil Fertility and Fertilizers, S.L. Tisdale and W.L. Nelson, eds. Macmillan Publishing, New York. 24. Wiedenfeld, R Sugarcane responses to N fertilizer application on clay soils. J. Amer. Soc. Sugar Cane Technol. 17: Wood, R.A Analogous nitrogen mineralisation effects produced by soils under grass leys and sugar cane. Int. Congr. Soil Sci. 8:

11 Muchovej: Nitrogen Fertilization of Sugarcane on a Sandy Soil: I. Yield and Leaf Nutrient Composition Table 1. Fertilizer rates at the first, second, third, and fourth split applications in the plant-cane, first ratoon, and second ratoon crops. 1 Fertilizer split Crop Plant-cane (2000) First ratoon (2001) Second ratoon (2002) N Treatment Date N P 2 O 5 K 2 O Date N P 2 O 5 K 2 O Date N P 2 O 5 K 2 O kg ha -1 kg ha -1 kg ha -1 First High Dec. 2 Mar. Mar. Medium Low Second High Apr. Apr. May Medium Low Third High June June July Medium Low Fourth High Aug. Aug. Sept. Medium Low Total High Medium Low Sources for N, P, and K were ammonium nitrate, triple superphosphate, and muriate of potash, respectively, with the exception of the first fertilizer split; plant-cane crop received N sources as ammonium sulfate and coated urea while the first and second ratoon crops received N sources as two-thirds ammonium nitrate and one-third ammonium sulfate. 2 December 9-13, 1999 was the planting date. 220

12 Journal American Society Sugar Cane Technologists, Vol. 24, 2004 Table 2. Mean squares of CP production data in response to three N rates (170, 280, and 390 kg N ha -1 yr -1 ) split into four applications for each year. Sucrose Source df concentration Stalk wt. Stalk no. 1 Cane yield Sugar yield (x 10 3 ) Nitrogen 2 Mean squares 9.98 ns * ns ns 8.00 ns Harvest ** ns ns ** Nitrogen x Harvest ns 0.33 ns 0.59 ns 0.10 ns Crop ** ** * ** ** Nitrogen x Crop ns 7.44 ns ns ns 0.29 ns Harvest x Crop * 1.03 ns 0.27 ns 0.21 ns Nitrogen x Harvest x Crop ns ns ns 0.20 ns ns, nonsignificant; *, **, significance of P < 0.05 and 0.01, respectively. 1 One stalk count was obtained for each crop in October or November. 221

13 Muchovej: Nitrogen Fertilization of Sugarcane on a Sandy Soil: I. Yield and Leaf Nutrient Composition Table 3. Means of sugarcane and sugar yields of CP in response to three N rates (170, 280, and 390 kg N ha -1 yr -1 ) split into four applications for each year. N rate (kg N ha -1 yr -1 ) Crop Sugarcane yield (Mg ha -1 ) November January Plant-cane First ratoon Second ratoon Sugar yield (Mg ha -1 ) November January Plant-cane First ratoon Second ratoon November sample was not obtained for the plant-cane crop. Table 4. Means of leaf tissue N concentrations of CP in the top visible dewlap leaf (with midrib) in response to three N rates (170, 280, and 390 kg N ha -1 yr -1 ) split into four applications for each year. N rate (kg N ha -1 yr -1 ) Crop g N kg -1 May June 2 July Aug. Sept. Oct. First ratoon Second ratoon No samples were obtained during the plant-cane crop. 2 Tissue sampling dates were scheduled 4.5 and 4.0 wk following split application of N fertilizer. 222

14 Journal American Society Sugar Cane Technologists, Vol. 24, 2004 Table 5. Macro- and micro-nutrient concentrations in the youngest fully emerged leaf (with midvein) of first and second ratoon crops CP sampled four weeks following the second, third, and fourth split applications of N fertilizer. Sample time 1 Between Nutrient Crop 2 Second split Third split Fourth split L.S.D. (P<0.05) 4-wk post 4-wk post 4-wk post sample times g kg -1 N 1 R ns ns ns R P 1 R 1.52 * 1.62 ** 1.46 ** R K 1 R 6.70 ** ** ** R Ca 1 R 3.94 ** 2.83 ** 2.37 ** R Mg 1 R 1.31 ** 1.23 ** 0.88 ** R mg kg -1 Zn 1 R ns * ns ns 2 R Mn 1 R ns * ns ns 2 R ns Cu 1 R 4.47 ns 3.87 ns 3.71 ns ns 2 R Fe 1 R ns ns ** R B 1 R ** ns ** ns 2 R Na 1 R ** ns ** R Sampling times were at 4.5 and 4.0-wk following the latter three-split application of fertilizer in the first-ratoon and second-ratoon crops, respectively. 2 Crop: 1 R means first ratoon crop and 2 R means second ratoon crop. 3 Between crops within sample time: ns, nonsignificant; *, **, significance of P<0.05 and 0.01, respectively. 223

15 Muchovej: Nitrogen Fertilization of Sugarcane on a Sandy Soil: I. Yield and Leaf Nutrient Composition Rainfall (mm) nd split 3rd split 4th split Plant (no water-table data recorded) Water-table elevation, soil surface = 0 (cm) Rainfall (mm) st split 2nd split 3rd split 4th split First ratoon Water-table elevation, soil surface = 0 (cm) Rainfall (mm) st split 2nd split 3rd split 4th split Second ratoon Water-table elevation, soil surface = 0 (cm) 0 J F M A M J J A S O N D Month Figure 1. Daily rainfall (vertical bars) and water-table depth ( ) for plant-cane, first ratoon, and second ratoon crops