Nutrients in Sugarcane | Sugarcane | Agronomy

In this article we will discuss about the Concentrations of major nutrients in sugarcane crop.

Nutrient Concentration:

As with other crops, sugarcane nutrient concentrations vary with age and among plant parts (Table 18.6).

Highest shoot nitrogen concentration occur in younger plants and tillers. The concentration declines with age due to production of structural tissues and retransolocation of nutrients to active meristems. Nitrogen deficient tillers may have only 4 to 6 green leaves instead of 12-14 on normal tillers.

Growing plant meristems need a continuous supply of phosphorus. Sugarcane accumulates inorganic phosphorus in the stem when the soil supply pennits. During periods of inadequate uptake, this inorganic fraction will be translocated to meristems. As in the case of nitrogen, shoot phosphorus concentration decreases with age.

The concentration of potassium in sugarcane varies among plant parts and with time. Potassium content of sugarcane shoots increases steadily with time and the stalk tissue usually contains more total potassium than green leaves. Since whole sugarcane stalks (including leaves) is removed from the field, sugarcane have higher fertiliser potassium requirement.

Deficiency of several nutrients leads to chlorosis. Nature of chlorotic symptoms due to micronutrient deficiency is given in Table 18.7.

Nutrient Uptake:

Sugarcane crop, producing a heavy tonnage, removes large amounts of nutrients from soil, which needs to be replenished in order to maintain soil fertility and hence sustained productivity. At Anakapalli (AP), uptake of nutrients was approximately 83 N, 37.2 P₂O₅ and 168 K₂O kg ha^-1 by a crop yielding 125 t ha^-1 of cane. As per the latest estimates on an average, sugarcane crop yielding 100 t ha^-1 removes 208 N, 53 P₂O₅, 280 K₂O, 3.4 Fe, 1.2 Zn, 0.6 Mn and 0.2 Cu kg ha^-1, respectively from soil.

Shrivastava et al (1988) reported distribution and partitioning of nitrogen in spring planted Co 1148 at Lucknow. Initially, more nitrogen was present in leaves. However, with the increase in number and size of stalks, the contribution of stalk nitrogen to total plant nitrogen also increased.

Nitrogen content of leaves declined after 206 days partly due to lower nitrogen content and partly due to less contribution of leaves to total dry matter of the plant. Stalks had higher structural nitrogen earlier to 176 days but at later stages, the proportion of storage nitrogen increased (Table 18.8).

Nitrogen uptake follows a sigmoid pattern. Around 1.75 per cent of total nitrogen accumulation is during first 45 days of planting followed by maximum uptake during tillering. Nitrogen uptake increases up to grand growth stage followed by a gradual decrease until harvest.

Absorption of major nutrients is most active beyond four months age and grand growth period coinciding with summer season. During the period (July to August), approximately 75 per cent of the nitrogen, 82 per cent of the phosphorus and 85 per cent of potassium are absorbed by a spring planted cane crop.

Around 40 per cent of the dry matter production occurs during July itself. Uptake of all the major nutrients per unit area (kg ha^-1) is near maximum soon after grand growth period. The uptake pattern of major nutrients (Table 18.9) shows maximum uptake at 180 days and decline thereafter.

Climatic conditions of the region have significant influence of nutrient uptake. In Deccan plateau region of Maharashtra, the crop removes 100 kg nitrogen, 161 kg phosphorus, 204 kg potassium while in coastal area of Andhra Pradesh 84 kg nitrogen, 37 kg phosphorus and 167 kg ha^-1 potassium. In Indo-Gangetic plains of Bihar, the uptake is 161 kg nitrogen, 14 kg phosphorus and 164 kg potassium ha^-1.

Determination of Nutrient Needs:

Soil Tests:

The rating of soils for available nitrogen and per cent organic carbon provides a reliable guide for ascertaining the requirements of fertiliser nitrogen up to a considerable extent. Although, response of sugarcane to applied nitrogen continues to be linear over a high range irrespective of soil types, the adverse effect of very high doses on juice quality are also inevitable.

Unlike nitrogen, adequate limits of phosphorus and potassium in soil should be maintained from very early stages of crop for quality cane crop. Approximate limits of major nutrients in the soil, based on soil testing are given in Table 18.10 for determining fertiliser schedule of cane crop.

Foliar Analysis:

Changes in plant composition with time during the crop growth have been used as quantitative index to arrive at fertiliser needs of sugarcane. However, between the times the tissues are analysed and fertilisers are applied and used by the crop, considerable damage has been done to the crop.

Table 18.7 gives adequate concentration of major nutrients in the plant and may serve as a guide to assess the fertiliser needs of sugarcane. On the basis of foliar analysis, Clements (1980) has developed an effective technique called crop logging.

Crop Logging:

It is a record of progress of the crop from germination until harvest. It is made up of pertinent data: chemical, physical and observational that reflect the welfare of the crop as it develops, the strategies invoked as crisis appears and the final results, good or bad, recorded for posterity. The crop log is a dynamic approach to crop production, designed to maximise yields using not only historical but also current data.

Beginning when the crop is about 3 months old, samples of certain leaf parts are taken every five weeks and analysed for various elements and materials. Each time, the new data are plotted to provide the grower with the information needed to guide the crop towards a successful harvest, very much as a patient’s chart in a hospital help the doctor decide what to do next.

In crop logging, sampling is done only for leaves +3, +4 and +6. Leaf+1 is the top most leaf, which may be well out or it may be just a needlepoint sticking out of the unrolling edge of the next order leaf. Counting down-word then establishes leaves +3, +4 and +6, which are removed by cutting across the attached sheath precisely at the nodal attachment.

When the fine tops have been taken apart, the 20 leaves are separated into sheaths and blades by placing a pocket knife blade underneath the sheath-blade joint and breaking the blade downword with one’s thumb.

The 20 sheaths are weighted and the total green weight when divided by five is the growth index, which is plotted on the log. The sheaths are then chopped into 1.0 cm length and dried at 80°C. The moisture index is calculated on green weight basis and the index is plotted. The dried material is ground and analysed for different nutrient elements.

Several countries have developed their own techniques to suit their needs. In India, studies on crop logging at Anakapalli (AP) indicated that 8-10 internode tissue are most appropriate. However, these could not be selected as index tissue because in the case of a 12 months crop, where fertiliser application is recommended to be completed within three months of planting, these tissues will become available only after 4 months.

Therefore, 3-6 leaf lamina for estimation of nitrogen and 3-6 leaf sheaths for estimation of moisture and other major and minor nutrients have been found quite appropriate. The values presented in Table 18.11 indicated the levels of nutrients and moisture at different ages of crop that recorded 125 t ha^-1 and nearly 20 per cent sucrose.

For the purpose of crop logging, the crop duration is divided into three phases: formative (120 days), grand growth period (150-270 days) and maturity (300-360 days). Elongating sheaths (3-6) on a sugar free dry weight basis for moisture, phosphorus, potassium and other nutrients have been identified as index tissues.

Nitrogen at or above 2 per cent, moisture 80 per cent, phosphorus and potassium at or above 0.08 and 1.99 per cent respectively have been computed as optimum levels at 3 months age of the crop at Anakapalli.

Moisture level in the cane remains high as long as nutrient deficiencies do not exist and as long as moisture is available in the soil. However, towards maturity, moisture should gradually come down to around 75 per cent for higher recovery. Leaf nitrogen begins dropping after 6 months age of the crop. Cane yield is positively correlated with sheath moisture in formative phase and with nitrogen in grand growth phase at Anakapalli.

Y = 498.64 + 6.066 x₁ + 18.72 x₂

where,

Y = cane yield in t ac^-1

x₁ = mean sheath (3-6) moisture % (60-120 days)

x₂ = mean sheath (3-6) nitrogen % (150-270 days)

In case, leaf nitrogen is below 2 per cent at 120 days, the quantity of nitrogen required to correct it is worked out by following the procedure indicated below:

Step I:

Critical value at the time of correction = 2% at optimum rate of N applied

Deficiency value = 1.71% N when fertiliser is not applied

Difference = 0.29 (A)

Step II:

Critical value = 2.0% N

N in fanners leaf samples (assumed) = 1.85% N

Difference = 0.15% N (B)

Step III:

Nitrogen index = B/A

Step IV:

Nitrogen to be applied (kg ha^-1) = B/A x age correction x (100 – x).

(x = N applied to the crop up to the age of crop at correction).

A few computed values of this index for important ages and sheath moisture are given in Table 18.12.

The range between adequacy and inadequacy of micronutrients is quite narrow and it has been felt that it is enough if it is ensured that they are present in amount at or over the adequacy levels indicated below:

Iron: 5 ppm (values up to 80-100 ppm are normal)

Manganese: 20 ppm (values up to 200 ppm are normal)

Zinc: 15 ppm (value up to 50 ppm are normal)

Copper: 4 ppm (value up to 15 ppm are normal)

Molybdenum: 0.08 ppm (value up to 1 ppm are normal)

Boron: 1 ppm (value up to 1 ppm are normal)

Soil Test-Crop Response:

Cane yields can be predicted to some extent on the basis of soil test values. When the level of nitrate nitrogen in the soil was 2 mg 100^-1 of dry soil, the cane yield was more than 100 t ha^-1 and the cane yield was around 150 t ha^-1 when the nitrogen level was 4 mg 100^-1 g or more.

In order to establish relationship between soil test values of major nutrients and nutrient content in index tissues of ratoon crop, Jafri (1974) conducted experiment with three levels of nitrogen (0, 150 and 200 kg ha^-1), three levels of phosphorus (0,50 and 100 kg ha^-1) and three levels of potassium (0, 75 and 150 kg ha^-1). Soil and plant samples were analysed at formative and grand growth period (Table 18.13).

Correlation coefficients and regression equations revealed that at both the stages, all the nutrients except phosphorus have significant correlation values.

At formative phase

For N: Y = 0.8815 + 0.0033 x. (r = 0.6784)

For P: Y = 0.2887 not significant

For K: Y = 0.8460 + 0.006 x. (r = 0.8506)

At grand growth period

For N: Y = 0.9519 + 0.0027 x. (r = 0.5766)

For P: Y = 0.647 + 0.003 x. (r = 0.7028)

For K: Y = 1.3129 + 0.0074 x. (r = 0.4395)

where, Y = index tissue composition (%) and x = soil composition (kg ha^-1).

Fertiliser Schedule:

Fertiliser nitrogen has been the main plank in the strategy for increasing sugarcane production. There is wide range in fertiliser use (112 to 504 kg N ha^-1) depending on the crop duration (12-18 months) of cane crop. The optimum rate in north India ranges between 112 and 224 kg N ha^-1.

For tropical belt, the recommended rates of nitrogen in kg ha^-1 are 112 to 400 for Andhra Pradesh, 187 to 375 for Karnataka, 175 to 275 for Tamil Nadu, 165 to 225 for Kerala, 150 to 400 for Maharashtra and 200 to 300 for Gujarat and Madhya Pradesh.

Sugarcane crop can utilise about 20 per cent of applied phosphorus. Response to added phosphorus can be expected in red, black and alluvial soils. Optimum rate varies between 50 and 180 kg P₂O₅ ha^-1 and the response varies from 0.05 to 0.025 t kg^-1 P₂O₅ in sandy and sandy loam soils. In general, recommended rates of phosphorus in kg ha^-1 are 50-80, 30-90, 120-180, 60-100 in north, south, west and eastern India respectively.

Sugarcane removes enormous quantity of potassium from soil, even up to 900 kg ha^-1, which could be termed luxury consumption. Response to applied potassium is expected in red and black soils. Recommended rates of application vary from 30 to 186 kg K₂O ha^-1 with response ranging from 0.02 to 0.15 t kg^-1 applied potassium. Recommended rates of potassium are 40-90, 75-190, 120-150 and 60-120 kg K₂O ha^-1 in northern, southern, western and eastern India respectively.

Rates of fertilisers recommended in different states of the country are summarised in Table 18.14. Each state has developed its own fertiliser schedule to meet the location specific needs.

As an example, Andhra Pradesh has recommended the following fertiliser schedule for a 12 months crop in different sugarcane growing districts:

The usefulness of organic manures is due to its contribution to general improvement in physical and biophysical properties of soil, which are indirectly useful in plant nutrition and maintenance of soil heath.

In addition to inorganic fertilisers, application of FYM or compost around 101 ha^-1 is, generally, recommended throughout the country. It should be incorporated 4 to 6 weeks before planting. If they are not available, green manuring with legumes may be done and field prepared after incorporating the green manure crop. In Bihar, Tamil Nadu and Karnataka, use of press mud is also common.

Sugarcane is benefited by biofertilisers. Field experiments with Azotobacter or Azospirillum indicated a saving of 35 kg N ha^-1. The use of Azotobacter culture at 5 kg ha^-1 along with 4 t ha^-1 of press mud increased cane yield with net saving of 25 kg N ha^-1.

The use of Acetobacter diazotrophicus as bioinoculant showed positive effect on plant growth not only due to its nitrogen fixation but also due to production of growth promoting hormones. Similarly, phosphate solubilising bacteria (Bacillus, Achromobacter, Acrobacter) and fungus (Aspergillus, Penicillium) can increase the phosphorus availability for higher can yield.

Wherever sulphur deficiency is observed, 50-100 kg S ha^-1 elemental sulphur may be mixed with soil prior to planting. Among the micronutrients, zinc and iron deficiencies are frequently observed. When sugarcane is grown after rice, zinc deficiency is common. It can be corrected by soil application of 25 kg Zn SO₄ ha^-1 once in 2-3 years. Lime induced iron chlorosis can be corrected by soil application of 25 to 50 kg Fe SO₄ ha^-1 or foliar spray (2% Fe SO₄).

Time and Method of Application:

Entire recommended dose of nitrogen should be applied within 100 days after planting, irrespective of duration of the variety.

In subtropical India, half of the recommended dose of nitrogen has to be applied at planting and the remaining half top-dressed before the onset of monsoon. In higher nitrogen doses, split applications at 45 and 90 days after planting may be followed.

In Bihar, 130-140 kg N ha^-1 is recommended with two-thirds applied at planting and the remaining one-third in two equal splits at 45 and 90 days after planting. Nitrogen as topdressing should be band placed near the plant. If applied at final earthing up (95 days), it has to be placed in a hole near the plant.

In general, entire recommended doses of phosphatic and potassium fertilisers are applied as basal dose before planting. However, in some states like Andhra Pradesh, potassium fertilisers are recommended in two splits at planting and at 90 days after planting.