1. Response of physiological and biomass production of baby spinach (Spinacia oleracea L.) leafy vegetable to nitrogen, phosphorus and potassium nutrition NEMADODZI EL, MAKUNGU M, P., ARAYA H, AND MUDAU, FN 1

2. Introduction Baby spinach (Spinacia Oleracea L.) Belongs to the family Amaranthaceae Annual cool season crop Green leafy vegetable predominantly eaten raw Leaves are small, not longer than 6cm Sweet tender, smoother than semi-savoy spinach 2

3. Justification of the study Baby spinach is a relatively new crop in South Africa, and the demand for baby spinach exceeds supply Farmers are predominantly cultivating normal spinach Data on the recommended rates of major nutrients such as N, P and K and combination NPK are not readily available in South Africa 3

4. Objectives of the study The effect of different N, P and K applications on the growth and development of baby spinach To investigate the interactive effect of combined NPK nutrition on the growth and development of the plants 4

5. Experimental site The trail was conducted at the Agricultural Research Council, Vegetable and Ornamental Plant Institute 25 Km North of central Pretoria GPS coordinates 25°59” S; 28°35”E The farm covers 4000 ha, of which only 650 ha is under irrigation 5

6. Experimental design and treatment details Three parallel trials for N, P and K and interactive trials were arranged in RCBD 5 treatments, replicated 4 times Sub plots were 2x2 m in size 3 rows with 10 plants each Inter-row spacing of 20cm, intra- row spacing of 10cm 6

7. Experimental design and treatment details Cv. Ohio cultivar seeds were planted in seedling trays filled with media from Hygromix Germinated after 5 days Transplanted done in two weeks Nitrogen and phosphorus treatments consisted of 0; 45 kg/ha; 75kg/ha; 105 kg/ha 120kg/haN/P Potassium treatments consisted of 0; 63 kg/ha; 85kg/ha; 127 kg/ha; 148 kg/ha 7

8. Treatment combinations trials After parallel N, P and K trials, the combined NPK trial was conducted, consisting of 5 treatments Combined NPK: 0; 30: 30: 45; 45:45:63 kg/ha; 60:60:78 kg/h and 75:75:93 kg/ha arranged in a RDCD replicated three times 8

9. Experimental design and treatment details Lime ammonium nitrate (28% N kg/ha) was supplied as the N fertiliser source Phosphorus was supplied in the form of super phosphate (83% P kg/ha) Potassium was supplied in the form of potassium chloride (50% K kg/ha) 9

10. Parameters recorded Data plants were sampled at 35 days after planting (DAP) Parameters recorded were biomass production (fresh mass, dry mass, root length, fresh root mass, dry root mass) Chlorophyll content Stomatal conductance above Stomatal conductance below 10

11. Cont… Leaf area index (LAI) Leaf protein percentage Total leaf nitrogen/phosphorus/potassium Leaf nitrate 11

12. Statistical analysis Treatment sums of squares were partitioned into linear and quadratic polynomial contrast using SAS version 14.1 12

13. Biomass production parameters of baby spinach in response to Nitrogen nutrition Applied N (Kg/ha) Fresh mass(g) per plant Dry matter (g) per plant Root length (cm) Fresh root mass (g) per plant Dry root mass (g) per plant Leaf protein (K) % Total leaf K % Leaf nitrate % Leaf protein in % 012.43d2.33c14.50b1.84a0.460a1.34b 0.02b8.3b 4537.62ab5.43b16.00b0.54a0.150a4.01a 0.04b25.0a 7545.81a10.29a21.50a0.47a0.115a4.26a4.31a0.23b26.6a 10527.89bc10.20a20.50a0.92a0.315a4.22a4.34a0.57b26.3a 12021.49cd8.91a15.00b0.37a0.090a4.22a4.54a1.33a26.5a 13

14. The application of different nitrogen levels did not have any significant effect on root mass. Nitrogen applied linearly increased the percentage protein content to 4.26% of baby spinach as compared to control. The significant increases varied with the applications of 0 to 45 kg/ha Percentage leaf nitrogen of baby spinach showed a significant increase at 45 kg/ha Where high nitrogen treatment was applied at 120 kg/ha, a significant percentage increased in the nitrate content level of 1.33% was observed All treatments linearly increased the percentage leaf protein contents compared to the control 14 Summary

15. Physiological parameters of baby spinach in response to N nutrition Nitrogen treatments ranging 0 to 45 kg/ha quadratically improved -chlorophyll content, -Upper lower stomatal conductance and as well as leaf area Applied P (Kg/ha) Chlorophy ll Content Stomatal conductan ce (Upper) mmol/m 2 / s Stomatal conducta (Lower) mmol/m 2 / s Leaf Area Index 0151.08c815.0b743.73b2.90b 45338.38a907.2a819.48a3.58a 75437.78a1197.7a781.93a3.78a 105370.85a937.59a866.30a4.08a 120233.50b865.3b921.70a4.25a SignQQQQ 15

16. Biomass production parameters of baby spinach in response to Phosphorus nutrition Applied P (Kg/ha) Fresh mass(g) per plant Dry matter (g) per plant Root length (cm) Fresh root mass (g) per plant Dry root mass (g) per plant Leaf protein (P) % Total leaf P % Leaf nitrate % 03.54b0.23a7.75a0.21a0.09a0.53b2.13b0.02a 455.69b0.15b5.50a0.24a0.11a0.97a3.42ab0.06a 7513.04a2.69a10.25a0.23a0.11a0.95a4.25a0.09a 10512.94a1.21b8.25a0.25a0.06a0.95a4.22a0.09a 12013.83a1.24b9.75a0.42a0.08a1.13a4.32a0.14a SignQQNS QQNs 16

17. Physiological parameters of baby spinach in response to P nutrition Applied P (Kg/ha) Chloroph yll Content Stomatal conductan ce (Upper) mmol/m 2 / s Stomatal comnduc ta (Lower) mmol/m 2 /s Leaf Area Index 062.78c59.53c65.00b80.4b 4569.00b72.05a71.70a9.40b 75171.35a114.40a64.93a21.18a 10590.45b61.50a42.23b17.37a 12095.28b39.78a53.40b17.87a Sign. Level 0.0001 All phosphorus treatments significantly increased the chlorophyll content of baby spinach, from 0 to 171.37 nm Adaxial stomatal conductance was not influenced by different rates of phosphorus application However, applying phosphorus at 45 kg/ha significantly influenced the abaxial stomatal conductance by 71.70 mmol/m 2 /s 17

18. Biomass production parameters of baby spinach in response to potassium nutrition Applied K (Kg/ha) Fresh mass(g) per plant Dry matter (g) per plant Root length (cm) Fresh root mass (g) per plant Dry root mass (g) per plant Leaf protein (K) % Total leaf K % Leaf nitrate % 01.25a0.27a8.00a0.59a0.26a 1.74b0.03a 631.13a0.26a5.25a0.37a0.06a0.36a2.30a0.08a 853.69a0.99a9.50a0.97a0.16a0.31a2.32a0.09a 1271.32a0.24a6.25a0.43a0.06a0.15a1.79b0.49a 1481.65a0.33a6.00a0.46a0.07a0.20a1.83b0.04a Respons e Ns 0.05Ns 18

19. Physiological parameters of baby spinach in response to potassium nutrition The application of potassium caused a quadratic response in the leaf area index of baby spinach at 63 kg/ha Applied potassium (kg/ha) Chlorophy ll content (nm) Stomatal conductan ce- adaxial (upper) mmol/m 2 / s Stomatal conductan ce – abaxial (lower) mmol/m 2 / s Leaf area index 080.05a32.25a36.93a0.91b 6366.30a42.00a38.00a1.31a 8581.73a39.55a39.28a1.02a 12748.28a43.03a41.38a1.02a 14853.78a48.47a47.43a0.74b ResponseNs Q 19

20. Biomass production parameters of baby spinach in response to combined NPK nutrition The combination of NPK significantly increased fresh and dry mass compared to control, stomatal conductance (upper and lower) No significant differences in leaf area were observed following applications of combined NPK nutrition None of the combined treatments improved root length, fresh root mass and dry root mass 20

21. Conclusions Growth and development of baby spinach was significantly improved by the fertilisers applied as well as fertiliser rates Adequate application of nitrogen and phosphorus fertiliser at 45 kg/ha improves plant growth parameters significantly, leading to quadratic effect on yield, dry matter, chlorophyll content and leaf area Potassium did not exhibit any significant effect Combined NPK fertilisers applied at a rate of 45:45:60 kg/ha had a significant effect on the yield as well as dry matter of baby spinach 21