1. SHW 3002 ANIMAL AGRICULTURE1 NUTRIENT REQUIREMENTS OF PASTURES

2. Why pastures have to be fertilized Nutrients are removed from soil by pastures Soil is not able to completely supply the required nutrients

3. Nutrient uptake per year (kg/ha) SpeciesYieldt/haNPKCaMg Brachiaria ruziziensis 32.93335444215077 Pennisetum purpureum 27.73327055410569 Panicum maximum 25.331748399163109

4. Deficiency Symptoms NITROGEN : General chlorosis of leaves with older leaves first showing symptoms

5. NITROGEN DEFICIENCY Potato leaves: Left : normal green leaf with sufficient nitrogen supply Right : nitrogen deficient leaf, pale green and yellow tinted

6. Deficiency symptoms Phosphorus – Leaves become purple or red in the veins. Early symptoms, leaves dark green in colour

7. PHOSPHORUS DEFICIENCY May develop purplish or reddish colour on leaves Premature leaf loss Poor root development Delayed maturity Decreased yield Rice plant under P-deficiency, stunted with limited tillers, narrow, short, erect and dirty dark green leaves.

8. Deficiency Symptoms Potassium (K) – yellow spots leaves scorching on leaf margins and leaf tips

9. K deficiency in maize K deficiency in riceK deficiency in alfalfa K deficiency in maize

10. Deficiency symptoms Magnesium – Interveinal chlorosis and necrosis. Deficiency causes hypomagnasaemia in animals

11. Lower leaf interveinal chlorosis in Gerbera. Geranium - lower leaf interveinal chlorosis. Notice the initial (left) versus advanced (right) interveinal chlorosis.

12. Fertilizers N – urea (contains 46% N) P – Triple Superphosphate (TSP) contains 21% P Rock phosphate (about 15% P) K – Muriate of Potash (contains 50% K)

13. Basal Fertilization During Planting – N – 50 kg/ha P – 50 kg/ha K – 50 kg/ha

14. How much fertilizer? 50 kg N = 100/46 x 50 kg urea 50 kg P = 100/21 x 50 kg TSP 50 kg K = 100/50 x 50 kg MOP

15. Maintenance Fertilizer Pure grass pastures - grazed N = 200 to 400 kg/ha per year –Applied 4-6 times per year P = 40-80 kg/ha K = 75-100 kg/ha –Applied 1-2 times a year

16. Maintenance Fertilizer Grass Legume Pasture N = 0 P = 40 – 80 kg/ha K = 35 – 60 kg/ha –Applied 1-2 times a year Micronutrients –5-8 kg/ha Copper sulphate –5-6 kg Zinc sulphate –200 g/ha molybdenum

17. Cut Fodder Grasses N – 50 kg/ha (after every cut) P – 40 kg/ha (after 3 cuts) K – 50 kg/ha (after 3 cuts)

18. NITROGEN

19. Importance of N in pastures Needed in large quantities for maximum growth – up to 800 kg/ha per year Most soils cannot supply the required rate N from fertilizers are soluble and easily leached N supply also affects protein content

20. N effects on dry matter yield

21. N effects on crude protein content

22. Sources of N Organic matter in soils N fertilizers N fixation by legumes N fixation by bacteria and algae In rain water

23. Nitrogen in Soils Stored in organic matter to depth of 90 cm from surface decomposition Nitrate 35 – 50 kg/ha per year

24. Biological N fixation (Bionif) Legumes as host in symbiotic association with Rhizobium Rhizobium forms nodules in roots Effective nodules are large and pink in colour (leghaemoglobin) Ineffective nodules are small in size and pale in colour

25. Biological N fixation

26. Rhizobium converts N from atmosphere into nitrite and nitrate Rhizobium requires supply of micronutrients such as Mo, Cu, B for this process Rhizobium is inhibited by presence of nitrates in soils

27. Amount of N fixed by legumes Varies with types of legumes and Rhizobium strains Temperate legumes (e.g. in NZ) – 280-400 kg N/ha per year Good tropical legumes : 170 – 280 kg N/ha per year Moderate tropical legumes : 55-170 kg N/ha per year

28. Rhizobium inoculation Inoculation necessary only when soils have never had legumes grown on it Rhizobium is cultured in peat Seeds of legumes are mixed with peat culture before sowing Use of sticker and pelleting with TSP helps in inoculation

29. Recycling of N 75% of N ingested by animals are returned through urine, but 45% is lost through volatilization or leaching 17% of N ingested by animals are returned through faeces and 6% lost through volatilization and leaching

30. N Cycle

31. Transfer of N from legumes to grass Direct transfer (amino acids from roots of legumes to grass) Decomposition of roots and rhizobium (1-5 kg N/ha per year) Decomposition of leaves and stems of legumes Through grazing animals (85% of N is returned)

32. Problems in maintaining legume- grass pastures Legumes are intolerant of heavy grazing Many pasture grasses dominate legumes when soil fertility is high Animals sometimes select for legumes Legumes are sensitive to nutrient deficiencies

33. Grass-legume vs Grass-N Low cost Limited yield High nutritive quality Not tolerant to heavy grazing Not suitable for cut and carry High cost of fertilizer High yields Moderate nutritive quality Tolerant to heavy grazing Suitable for cut and carry

34. END