CNP Measurement By Picrate Method

Transcription

1 CNP Measurement By Picrate Method Dr Richardson Okechukwu

2 Cyanogenic potential ti (CNP) No acyanogenic cassava has been reported; glucosides, linamarin, and lotaustralin are found within all cassava plants. On contact t with the enzyme linamarase (released upon tissue damage, as in many forms of processing), acetone cyanohydrin and glucose are produced. The acetone cyanohydrin either spontaneously breaks down or it is acted upon by the enzyme hydroxynitrile lyase to produce acetone and hydrogen cyanide.

3 Cyanogenic potential ti (CNP) There are large effects of environments on root cyanogens In practice, low CNP varieties are desirable for both safe human and animal utilization. Studies have established a relationship between CNP levels in cassava and starch physical properties (viscosity, i cooking time, gel instability, and gelification i index). Bitter varieties (which usually happen to have high CNP level) are reported to have higher starch content, and make better quality products that even store better.

4 Materials required for Picrate test Knives, Scissors glass tubes or vials (12 cm long with tightly fitted rubber stops) p) scoring scale. Consumables required include filter papers (Whatman No. 1.6 cm x 1 cm) picric acid anhydrous sodium carbonate, and toluene. Please note that both picric acid and toluene (methylbenzene or phenyl methane) are hazardous chemicals, and NEED TO BE HANDLED WITH EXTREME CARE AND WITH APPROPRIATE PROTECTION.

5 Process Steps CNP varies considerably between plants, analysis will be done using 4 plants/clone, and on 3 roots per plant. 1. For each root sample, make a cross-sectional cut at the mid-root position. 2. Pinpoint the mid position between the peel and the center of the parenchyma (root flesh) and make a 1 cm 3 cube cut. 3, Place the cut root cube into a glass tube and add 5 drops of toluene onto it; tightly seal the glass tube with the stopper. 4. Take a strip of Whatman filter paper p and dip it into freshly prepared alkaline picrate mixture until saturated.

6 Process Steps 5. Suspend the picrate-saturated filter paper p above the cut root cube in the glass tube; ensure that the tube is tightly fitted with the rubber stopper 6. After hours, score for color intensity it using the 1 9 scale below.

7 The generated data should be recorded in the format shown

8 8

9 Soil fertility and fertilizer use in cassava farm Dr Richardson Okechukwu

10 You can produce to gain Or produce to lose 10

11 Natural Resource Management Low native soil fertility Soil exposed to erosion Good canopy Increased leaching (N and K; also Ca, Mg, S) serious under high rainfall Soil temperature t increases, accelerating organic matter decomposition (C, N and S loss) Climate change, less water and nutrient uptake CASSAVA: CROP REMOVAL 10 tons/ha tubers: 30 kg N, 4 kg P, 20 kg K 50 tons/ha: 140 kg N, 20 kg P, 125 kg K +removal of planting sticks: 340 N, 40 P, 270 K It is not only cassava that Leaf harvest increases N removal does this 11

12 Fertilizers for cassava LSD = Percent change: Percent change in Fresh root yield Fresh yield (t/ha) F NF 4(2) / / / / / / B/ B/ / / / / / / / / /1089A 96/ / / / / / / / / / / / / / / / / / / /6012 M98/0028 M98/0040 M98/0068 TME419 TMS30572 Root number Fresh yield (t/ha) Dry matter (%) Source df SS P>F SS P>F SS P>F Loc < < < Fert Loc*Fert < < Clone < < < Fert*Clone R-square CV Type (macro and micro nutrients) Rate by varieties Time of application 12

13 Soil fertility management and fertilizer recommendation Soil fertility is an inherent nature of the soil in terms of its nutrient status and its ability to supply these nutrients in the accurate amount and right proportion to the use of plants growing in the soil. The essential nutrients are involved in the metabolism of the plants: C, H, O, N P, S, Ca, Mg, K, (macronutrients) Mn, B, Zn, Fe, Cl, Mo, and Cu (micronutrients). The absorption of these nutrients by plants depends on some external factors such as availability of nutrients, soil humidity, aeration, organic matter content and ph. Soil fertility therefore focuses on adequate and balanced supply of nutrients to satisfy the needs of the plants, avoiding toxic concentrations.

14 Soil fertility management therefore involves agricultural practices which are vital in ensuring adequate nutrient status in the soil for efficient crop production. These practices include application of organic and inorganic fertilizers, mulching, green manuring. Application of chemical fertilizers is generally more practical and economical when cassava is grown at a somewhat large scale. The quantity of inorganic fertilizer applied in a farm depends on the amount of nutrients available in the soil which that soil can supply to the plants. The quantity of fertilizer applied is the difference between the nutrient available in the soil and the standard critical level of the nutrient required for the growth of the crop.

15 Required soil conditions Cassava will grow in most soils but it prefers slightly acidic (ph ), loose or loam soil with good drainage. The tubers shall certainly rot if planted in low-lying areas prone to flooding.

16 Soils on which h cassava is produced d and their principal nutritional constraints for the crop. Nutritional constraints Soil Order Acidity N P K Ultisols Alfisols Oxisols Entisols Inceptisols Mollisols Vertisols Aridisols Histosols Cassava can grow well on Mollisols and the better-drained Vertisols, but these highly fertile soils are generally used for higher-value crops such as sugarcane, maize, sorghum, soybeans and cotton Source: Agro-ecological Studies Unit, CIAT, 1985

17 The average highest percent yield increase due to fertilization and value/cost ratio (VCR) for cassava as compared to other crops in various countries. Average best Country Crop No. of trials % Response VCR Cassava Maize Cotton Beans Rice Soybean Sugarcane Cassava Maize Beans Forage Potatoes Wheat Cassava Maize Groundnut Cotton Cowpeas Cassava Maize Yams Rice Source: FAO, Cassava Rice Sorghum Groundnut Soybean

18 Cassava is quite sensitive to over-fertilization, especially with N, which will result in excessive leaf formation at the expense of root growth. High N applications reduce the harvest index (HI), root yield, starch and increase the HCN content of the roots. Nutrients generally interact with each other, and the excessive application of one nutrient may induce a deficiency of another. Howeler et al. (1977) and Edwards d and Kang (1978) have shown that high rates of lime application may actually reduce yields by inducing Zn deficiency.

19 In Africa, significant responses to K have been found on strongly acid soils of eastern Nigeria (Okeke, unpublished) and on slightly acid soils (0.23 me K/100 g) of southwestern Nigeria (Kang and Okeke, 1984). Obigbesan (1977a) did not observe a significant K response on three soils of western Nigeria, nor did Takyi (1972) in Ghana. In Madagascar, however, Roche et al. (1957) and Cours et al. (1961) found that K was the main limiting nutrient, and applications of 110 kg K 2 O/ha were recommended (Anon., 1952; 1953).

20 Nitrogen Nitrogen is a basic component of protein, chlorophyl, enzymes, hormones and vitamins. It is also a constituent of the cyanogenic glycosides, linamarin and lotaustralin, which produce hydrocyanic acid (HCN) when cells are damaged. HCN is the bitter, highly toxic component of cassava leaves, stems and roots, which must be eliminated by drying or cooking the roots before consumption. Cassava plants suffering from N-deficiency may not show any visible deficiency symptoms, but are shorter and grow less vigorous than normal. In some varieties and under severe N-deficiency leaves are slightly lighter green in color, the chlorosis being rather uniform throughout the plant.

21 Phosphorush Phosphorus is a basic component of nucleoproteins, nucleic acids and phospholipids as well as all enzymes that play a role in energy transfer. Phosphorus is an important element for the process of phosphorilization, photosynthesis, respiration and the synthesis of carbohydrates, proteins and fats. Through h these processes an adequate P supply is essential for the synthesis of starch and thus for normal root production. Roots contain relatively l small amounts of P, and P removal from the soil in the root harvest is therefore much lower than that of N or K. P deficient plants seldom show clear deficiency symptoms; instead, they are shorter and less vigorous, have thinner stems and smaller and narrower leaves than normal plants. Root yields can be seriously depressed by P-deficiency.

22 Potassium Potassium is not a basic component of protein, carbohydrates or fats, but plays an important role in their metabolism. Potassium stimulates net photosynthetic activity of a given leaf area and increases the translocation of photosynthates to the tuberous roots. This results in low carbohydrate levels in the leaves, further increasing photosynthetic activity (Kasele, 1980). Blin (1905), Obigbesan (1973) and Howeler (1998) reported that K application not only increased root yields but also their starch content. In general, root starch content increases up to kg K 2 O/ha and then levels off or decreases at higher rates of K application. Like N and P, deficiency of K results mainly in reduced plant height and vigor. Stem internodes are markedly reduced and the upper stem tends to lignify prematurely, resulting in a zigzag growth. In general, stems are thick and highly branched, producing a prostrate growth habit.

23 Effect of Fertilizers on Root Quality Fertilizer applications do not only affect cassava yields, but also the quality of the harvested roots, primarily the dry matter and starch contents of the roots as well as the HCN contents, and thus the bitterness of the roots. Chan and Lee (1982) reported that root starch contents increased with K application, reaching a maximum of 36.8% with the application of 180 kg K 2 O/ha. Higher K rates decreased the starch content. CIAT (1980) also reported an increase in starch content from 26.7 to 34.2% with the application of 50 kg K 2 O/ha, above which there was no significant effect.

24 Calculating Fertilizer Rates from Nutrient Recommendations Soil test recommendations are given in lb/ac or kg/ha of nutrients. To determine the fertilizer rate for a particular nutrient, multiply the rate of the desired nutrient by 100 and divide by the percentage of the nutrient in the fertilizer. Example 1 Recommended rate of N is 80 lb/ac Using , the rate of fertilizer required is: (80 x 100) / 46 = 174 lb/ac Example 2 Recommended rate of P 2 O 5 is 40 lb/ac Using , the rate of fertilizer required is: (40 x 100) / 52 = 77 lb/ac 77 lb/ac of would also supply (11/100) x 77 = 8.5 lb/ac of N. Example 3 Recommended rate of K 2 O is 15 lb/ac. Using , the rate of fertilizer required is: (15 x 100) / 60 = 25 lb/ac

25 Example: You have a 22.68kg bag of fertilizer that you want to apply to a lawn at a rate of 0.45kg nitrogen per 1000 sq ft. How much of the fertilizer will you need to apply per 1000 sq ft? The quickest way to solve this problem is to ignore the weight of the fertilizer bag and simply divide the amount of nitrogen desired (0.45kg nitrogen per 1000 sq ft) by the percentage of nitrogen in the bag (26%). When using percentages in calculations, convert the number to its decimal form (for example, 26% = 0.26; 5% = 0.05). (0.45kg nitrogen per 1000 sq ft) 0.26 = 1.73 kg of a fertilizer is needed to supply 0.45kg nitrogen per 1000 sq ft.

26 Example: Find out how much phosphate and potash you are applying to the turf when you apply 1.72kg of the fertilizer per 1000 sq ft. Multiply pythe amount of fertilizer you are applying ppy g( (1.72kg gper 1000 sq ft) by the percentage of phosphate in the bag (5%). Do the same for potash (10%). Remember to convert the percentages of phosphate and potash to their decimal forms. (1.72kg fertilizer per 1000 sq ft) 0.05 phosphate = 0.086kg phosphate per 1000 sq ft (1.72kg fertilizer per 1000 sq ft) 0.10 potash = 0.172kg potash per 1000 sq ft

27 Determining the area that a bag of fertilizer can cover and how many bags are needed to cover large sites Example: How much area can be covered with a 22.68kg bag of at the rate of kg nitrogen per 1000 sq ft? Now that you know 1.72kg of fertilizer will cover 1000 sq ft, determine how many times 1.72kg goes into 22.68kg kg 1.72kg = Now multiply 13.2 by 1000 sq ft: sq ft = 13,200 sq ft. Thus, a 22.68kg bag of covers 13,200 sq ft at a rate of kg nitrogen per 1000 sq ft. Example: How many 22.68kg bags of will you need to fertilize a 30,000 sq ft lawn at kg nitrogen per 1000 sq ft? If a 22.68kg bag of fertilizer covers 13,200 sq ft at kg nitrogen per 1000 sq ft, determine how many times 13,200 goes into 30, ,000 13,200 = 2.3 bags of will cover 30,000 sq ft.

28 Fertilizers commonly used as sources for N, P, K Fertilizer abbreviation Fertilizer Nutrient (weight percentage) AN Ammonium nitrate 33-34%N AS Ammonium sulphate 21%N ASN Ammonium sulfate nitrate 26%N CN Calcium nitrate 15%N CAN Ammonium nitrate/calcium 20-28%N UAN Urea ammonium nitrate 28-32%N APN Ammonium phosphate nitrate to APS Ammonium phosphate sulfate DAP Diammonium phosphate MAP Monoammonium phosphate NK Nitrate of potash MOP Muriate of potash 60-62%K 2 O SOP Sulfate of potash 50% K O 2 SSP Single supephosphate 16-22% P O 2 5 TSP Triple supephosphate 44-48% P O 2 5

29 More Fertilizer calculations Fertilizer recommendations are expressed in kilograms of nutrients per hectare (kg/ha) in the order N-P O5-K O (or N-P- 2 2 K). Based on result of field trials or results of soil analysis, fertilizer rates are formulated. Example 1 - Calculation for combination of single element fertilizers (Kang, 1995): Given a recommended rate of 80N-30P 2 O 5-30K 2 O kg/ha, apply fertilizers using urea, triple superphosphate, and muriate of potash:

30 80kg/ha x 100 = 178kg/ha of urea 45% 30kg/ha x 100 = 67kg/ha of triple superphosphateurea 45% 30kg/ha x 100 = 50kg/ha of urea 60% Example 2 Calculation for combinations of single nutrient and compound fertilizers Given a fertilizer and urea (45%N), apply at the rate of kg/ha. Phosphorus and potassium must be calculated first. 30kg/ha x 100 = 200kg/ha of urea 15% 15% Therefore 200 kg of a compound fertilizer supplies only 30 kg of N per ha. This means one must yet supply another 50 kg of N by urea. 50kg/ha x 100 = 111kg/ha of urea 45%

31 Application rates Fertilizer recommendations for cassava when soil fertility is low are 90Kg/ha for N (196 Kg/ha of urea), 47 kg/ha P 2 O 5 or 20 kg/ha P or 288kg/ha of single superphosphate), and 75kg/ha K or 90 kg K 2 O (90 Kg of muriate of potash). Current Nigeria recommended 12:12:17+MgO Two doses, 1 MAP and 3 MAP

32 S i fertility Soil f i i management Poor soil = Poor yield High production cost Extensive farming Poor resource control

33 Thank you for your attention 33