Soil Fertility and Management Soil fertility Potential of

Soil Fertility and Management

Soil fertility Potential of the soil for supplying nutrient elements in the amounts, forms, and proportion required for the normal growth of specified plants. ¡ Concept of soil productivity but refers specifically only to the content, balance and availability of the chemical compounds in the soil that influence plant growth. ¡

The essential elements ¡ Essential elements are elements required by plants for their life processes. Three of the criteria used in establishing the essentiality of the plant nutrient are l l l Its necessity for the plant to complete its life cycle Its direct involvement in the nutrition of the plant The element must be completely irreplaceable by another element

Nutrient mobility in plant Mobile nutrients – symptoms of deficiency appear on the lower leaves ¡ Nutrients with limited mobility symptoms appear in the new leaves or growing points. ¡

Sources and available forms of nutrients/essential elements Source/kind of essential elements Available form Those derived from air and water 1. carbon from carbon dioxide in air 2. oxygen from carbon dioxide in air 3. hydrogen from water Gas Absorbed as H 2 O Those derived from soil solids (organic and mineral matter) a. Macronutrients – nutrients that are needed by plants in large amount 1. Nitrogen 2. Phosphorus 3. Potassium 4. Calcium 5. Magnesium 6. Sulfur NH 4+, NO 3 H 2 PO 4 - , HPO 4= K+ Ca 2+ Mg++ SO 4 -

Source/kind of essential elements a. Micronutrients – nutrients that are needed by plants in small amount 1. Copper 2. Iron 3. Manganese 4. Zinc 5. Boron 6. Chlorine 7. Molybdenum 8. Nickel Available form Ni 2+ Cu 2+ Fe+++, Fe++ Mn++ Zn++ H 2 BO 3 - , HBO 3= Cl. Mo. O 4=

Nutrient Availability Factors Availability factor – the relative ease in which a nutrient element is supplied by the soil to the plant. ¡ Capacity factor- refers to the capacity of the plants to absorb the nutrients ¡ Rate factor- refers to the rate of replenishments ¡

Mechanisms of supply of nutrients to plant root ¡ ¡ ¡ Root interception – the nutrients absorbed by the root as they ramify through the soil Mass flow – nutrients dissolved in soil water are transported to the root surface Diffusion – movement of nutrient ions through the soil water and from the exchange site to exchange site along the surface of soil particles.

Nutrient uptake by plants Passive ion uptake. Uptake or absorption of ions /nutrients that occur in the outer space thru diffusion or contact exchange ¡ Active ion uptake or absorption of nutrients that involves use of energy ¡

Quantitative expression of plant growth Growth, G, may be expressed as being equal to the product of the average rate, R, and then t (time) or G=Rxt

Soil fertility management Factors affecting decline of soil fertility 1. Crop removal of nutients 2. Leaching of nutrients 3. Gaseous losses of nutrients 4. Soil erosion losses

Methods of assessing or evaluating soil fertility Visual symptoms of nutrient deficiency ¡ Plant analysis ¡ Soil analysis ¡ Pot or field fertilizer trials ¡

Soil fertility management practices ¡ Liming acid soils l Liming materials a. agricultural limestone – Ca. CO 3, Ca. Mg (CO)3 b. oxides of lime – Ca. O, Mg. O c. hydroxides of lime – Ca(OH)2, Mg(OH)2

l Relative neutralizing power (RNP) of different forms of lime RNP of lime = Molecular weight of Ca. CO 3 Molecular weight of any liming material X 100

The neutralizing power of some liming material in their pure form LIMING MATERIAL Formula Calcium Carbonate Ca. CO 3 Calcium Hydroxide Ca(OH)2 Calcium Oxide Ca. O Magnesium Carbonate Mg. CO 3 Magnesium Hydroxide Mg(OH)2 Magnesium Oxide Mg. O Dolomite Ca. Mg(CO 3)2 Neutralizing power 100 135 179 119 172 250 109

Methods of determining lime requirement of soils 1. Veitch Method - addition of increasing amounts of 0. 04 N Ca(OH)2 to the soil samples, allowing them to stand for 30 minutes and their p. H’s would be determined. 2. Calcium carbonate incubation in the laboratory 3. Field or pot lime trials

4. Exchangeable aluminum index method L. R. = #me Al/100 g x 1. 5 = me Ca. CO 3/100 g 5. Aluminum saturation method

Soil processes and conditions affected by liming ¡ Volatilization of ammonia from ammonium-containing fertilizers Ca(OH)2 + (NH 4)2 SO 4 Phosphorus fixation 2 Al(OH)2+ + 2 H 2 PO 4 - Ca. SO 4 + 2 H 2 O + 2 NH 3 ¡ 2 Al(OH)2 PO 4

Forms and General Characteristics of Fertilizers ¡ ¡ ¡ Organic Fertilizer – are fertilizers that are either plant or animal origin Inorganic Fertilizer – these are fertilizers out of minerals or are products of chemical reactions of raw materials Liquid Foliar Fertilizer – these are solution of nutrients

General Characteristics of Organic and Synthetic Inorganic Fertilizers Parameter Nutrient Analysis Nutrient Availability Essential Elements Present Amount of Fertilizer Needed Effect on Soil Inorganic High Rapid N, P and K Organic Low Slow All Less More Acidifying Effect Improves Soil properties

Some Organic Fertilizers Farm Manures ¡ Compost ¡ Crop Residues ¡ Green Manures ¡

Inorganic Fertilizers The inorganic fertilizers that are commonly sold in the market are mostly synthetic. ¡ Undergone physical and chemical processing ¡ Analysis grade is the minimum guarantee of the nutrient content of the material expressed as % nitrogen (%N), % phosphorus as P 2 O 5 (% P 2 O 5), % potassium as K 2 O (% K 2 O). ¡

In fertilizer calculation, a sample formula to use is the following: Wt. of the nutrient needed Wt. of fertilizer materials= Nutrient content, % Problem: A fertilizer recommendation calls for the application of 90 -60 -30 kg of N, P 2 O 5 and K 2 O per ha. Calculate the weight of ammonium sulfate (20 -0 -0), ordinary superphosphate (0 -20 -0) and muriate of potash (0 -0 -60) needed for one hectare. (note: 1 bag of fertilizer = 50 kg).

90 Wt. of ammonium sulfate= = 428. 57 kg/ha or 9 bags 0. 21 Wt. of ordinary superphosphate = Wt. of muriate of potash = 60 = 300 kg or 6 bags 0. 20 30 = 50 kg or 1 bag 0. 60 The quantities of fertilizers needed per hectare the ff: 428. 57 kg ammonium sulfate 300 kg ordinary superphosphate 50 kg muriate of potash

Methods of Fertilizer Application Broadcast ¡ Band ¡ Foliar ¡ Ring Method ¡

Maintenance of Soil Organic Matter may be Accomplished by: Use of farm manures ¡ Use of poultry manures ¡ Use of green manures ¡ Use of crop residues ¡ Use of composts ¡ Cover cropping ¡ Fallowing ¡ Mulching ¡ Use of industrial and municipal by-products ¡

Review Questions for Soil Fertility and Management 1. The Haber Bosch process for making N fertilizer a. N 2 + N 2 O NH 3 b. N 2 + 3 N 2 2 NH 3 c. N 2 + 2 O 2 NO 3 d. N 2 + H 2 O NO 3

2. The highest analysis (grade) solid N fertilizer a. ammonium sulfate b. anhydrous ammonia c. urea d. ammonium nitrate

3. The reaction during biological N fixation a. N 2 nitrogenase NH 3 b. N 2 + H 2 O amino acid c. N 2 + H 2 O protein d. N 2 + H 2 ammonium sulfate

4. The enzyme needed to transform urea to (NH 4)2 CO 3 in soil. a. carboxylase b. anhydrase c. uric acid d. silicic acid

5. The weak acid formed upon hydrolysis and subsequent reaction of urea in soils. a. acetic acid b. carbonic acid c. uric acid d. silicic acid

6. The other essential nutrient element present in ammonium sulfate but absent in urea. a. calcium b. sulfur c. iron d. magnesium

7. The percent N, P 2 O 5 and K 2 O in a fertilizer is a. fertilizer ratio b. fertilizer grade c. fertilizer recommendation d. fertilizer brand

8. A single-element or straight fertilizer. a. complete fertilizer (14 -14 -14) b. ammonium phosphate c. urea d. all of the above

9. The fertilizer nutrients that are generally applied all at planting time (basal). a. N and P b. P and K c. N and K d. P and Ca

10. The fertilizer nutrients which are usually split applied. a. N and K b. P and K c. N and P d. N and S

11. The available form of nitrogen a. N 2 b. N 2 O c. NH 4+ d. NH 3 12. Enzyme in nitrogen transformation in legumes. a. Nitrogenase b. dehydrogenase c. decarboxylase d. anhydrase

13. This ratio determines mineralization rate of organic matter. a. N/S b. C/N c. P/N d. N/K 14. Application of N fertilizer in Alkaline soils causes a. NH 3 volatilization b. nitrification c. denitrification

15. This is an acid forming reaction of NH 4+ a. nitrification b. denitrification c. ammonification d. mineralization 16. This metal ion is usually present in toxic amounts in strongly acidic soils. a. aluminum b. calcium c. potassium d. magnesium

17. Binding of an organic compound and metal ion. a. coordination b. complexation c. chelation d. oxidation

18. Most micronutrients become less available at. a. decreasing soil p. H b. increasing p. H c. neutral p. H d. strongly acid p. H

19. When nutrients are immobile, deficiency first shows up in. a. youngest leaves b. oldest leaves c. senescent leaves d. stems

20. Deficiency of these elements causes chlorosis. a. N and Ca b. P and Ca c. N and S d. Fe and Cl

21. Deficiency of sulfur first shows up as chlorosis of. a. oldest leaves b. youngest leaves c. middle leaves d. stems

22. The suitable fertilizer for an alkaline N deficient soil. a. anhydrous NH 3 b. urea c. calcium nitrate d. Ammonium sulfate

23. The appropriate N fertilizer for a sulfur deficient soil. a. urea b. ammonium nitrate c. potassium nitrate d. ammonium sulfate

24. Application of fertilizer at planting. a. topdressing b. foliar c. band d. basal 25. Application of fertilizer after plant emergence a. basal b. topdressing c. foliar d. deep placement

26. Major agent of soil erosion in the Philippines. a. wind b. water/rainfall c. animal traffic d. wind and water

27. This conservation practice dissipates raindrop impact. a. terracing b. contour plowing c. mulching d. grassed waterways

28. The first stage in soil erosion is. a. soil particle detachment b. entrainment c. deposition d. water infiltration

29. Soil conservation practice where hedges are grown along the contour lines. a. bench terracing b. cover cropping c. alley cropping d. farm pond construction

30. Soil loss through erosion can be calculated by the. a. Mitscherlich equation b. Universal soil loss equation c. Einstein’s relativity equation d. trigonometric equation.

¡ 31. Sum of all tillage operation to conserve soil A) Soil Conservation ¡ B) Soil Management ¡ C) Soil tilth ¡ All of the above ¡

¡ a) b) c) d) 32. Natural process of erosion which is responsible for the formation of landscape Geologic Accelerated Geologic/accelerated none

¡ The first stage of erosion l l A) splash B) stream bank erosion C) gully D) sheet

¡ 34. The upper part of soil is washed away in more or less uniform layers l l A) splash B) stream bank erosion C) gully D) sheet

¡ 35. Small yet well-defined channels are formed l l A) rill B) stream bank erosion C) gully D) sheet

¡ 36. It is the advanced stage of rill erosion where farm implements cannot function its normal operation l l ¡ A) rill B) stream bank erosion C) gully D) sheet

¡ 37. Erosion caused by meandering of streams/rivers l l ¡ A) rill B) stream bank erosion C) gully D) sheet

¡ 38. Factors of soil erosion which refers to rainfall erosivity l l A) R B) K C) L D) S

¡ 39. Factors of soil erosion which refers to soil erodibility l l A) R B) K C) L D) S

¡ 39. Factors of soil erosion which refers to length of slope l l A) R B) K C) L D) S

One of the on-site effects of soil erosion ¡ A) loss of topsoil ¡ B) increased flood flows ¡ C) Siltation of dam ¡