Research Report

Effect of Plant Density, Nitrogen Fertilizer Application Rates and Soil Depth on Clonal Tea Soil Nutrient Content  

Kibet Sitienei , Kiplangat Kirui , David Kamau , John Wanyoko , Kimutai Langat
Tea Research Institute, Kenya Agricultural and Livestock Research Organization (KALRO), Kenya
Author    Correspondence author
Journal of Tea Science Research, 2016, Vol. 6, No. 7   doi: 10.5376/jtsr.2016.06.0007
Received: 27 Jan., 2016    Accepted: 16 Mar., 2016    Published: 07 Apr., 2016
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Preferred citation for this article:

Sitienei K., Kirui K., Kamau D., Wanyoko J., and Langat K., 2016, Effect of Plant Density, Nitrogen Fertilizer Application Rates and Soil Depth on Clonal Tea Soil Nutrient Content, Journal of Tea Science Research, 2016, 6(7), 1-5 (doi: 10.5376/jtsr.2016.06.0007)

Abstract

Trial on plant density which started in 1990 has revealed that in clonal tea, yield significantly increased with decrease in plant population density (ppd), with the highest ppd showing significantly lower yield than all the other ppd. However, this effect was opposite when the tea was young. It is not therefore known whether the same effect applies to nutrients content. This study was carried out to determine the effect of plant density of AHP S15/10 clonal tea plants and rates of nitrogenous fertilizer applied on soil content in Kericho, Kenya. Soil samples were collected from all the experimental plots. The samples were analyzed for their contents of macro and micro elements by ICPE spectroscopy. The results showed that plant density had no significant effect on the soil nutrients content. Nitrogen fertilizer application rates and depths of soil showed significant effects. Every element in the soils showed similar nutritional pattern for different nitrogen application rates across the four depths of the profile. However, the pattern was different for different plant density. Phosphorus content was least in the highest ppd.

Keywords
Clones; Concentration; Nutrient; Plant population density

1 Introduction

Tea is one of the most popular beverages and an important commercial crop spread over many areas of the world (Nath, 2013). Yield of leaf plucked from a field of tea is dependent among many factors, up on the extent to which the field is covered by the bushes. Cultural practices such as planting density have effects on yield (Kigalu and Carr, 2006). Tea is normally planted in single or double rows separated by 1.2 to 1.8 m between the rows to allow access to the bushes for plucking and maintenance (den Braber et al., 2011). Dense planting can improve the early yield and revenue, encouraging early establishment of plantlets and appropriate ground cover, reducing the cost of weeding and minimizing water losses by decrease of surface evaporation and run off (Kigalu, 2007a; Kigalu, 2007b). The yield gradually decreases with higher density as the plants continue to age. Trial on plant density experiment started in 1990 at TRI Kericho, Kenya has revealed that in clonal tea, yield significantly increased with decrease in plant population density (ppd), with the highest ppd showing significantly lower yield than all the other ppd after a certain time. The main sources of micronutrients in plants are their growth media, agro inputs and soil (Subbiah et al., 2007; Omwoyo et al., 2014). Plants take up the elements from the soil (Lasheen et al., 2008; Omwoyo et al., 2014). Several elements such as Ca, Na, K, Mg and Mn are present in mg/g quantities while elements such as Cr, Fe, Co, Ni, Cu, Zn, Se and Cd are present in µg/g level (Cao et al., 1998; Mokgalaka et al., 2004; Omwoyo et al., 2014). It is not therefore known whether the same effect applies to nutrients content. Therefore, it was deemed that the determination of effect of plant density of AHP S15/10 clonal tea plants and rates of nitrogenous fertilizer applied on concentration of macro and micronutrients in tea soil could help enhance the sustainability of tea cultivation.

 

2 Materials and Methods

Site description and experimental layout

The research used an existing experiment which was started in 1990 at Tea Research Institute, Timbilil estate, Kericho Kenya. The site is situated at an altitude of 2178 m asl, latitude 00 22’ S and longitude 350 21’ E and was a virgin forest prior to the start of experiment. The experimental design was a split-plot completely randomized block design with four main treatments (as plant population density i.e. 26,896; 13,448; 8,975 and 6,730 plants/ha) and four sub-treatments (as rates of nitrogen i.e. 80, 160, 240 and 320 Kg ha-1 year-1 as NPKS 25:5:5:5) replicated three times.

 

Samples collection

Soil samples were taken from four depths in all plots.

 

Soil samples

Soil were sampled from the field using an auger. They are transferred to clear polythene bags and labelled. Soil samples are taken to the drying shade to dry. This is the removal of moisture in the soil before they are sieved. When the soil samples are dry, they are sieved through a 2mm sieve. This is to obtain smaller particles which increases the ease of extraction by providing large surface coming in contact with the extractant. Soil pH (Thomas, 1996), phosphorus (Kuo, 1996), exchangeable potassium (Helmke and Sparks, 1996), exchangeable calcium and magnesium (Suarez, 1996) and available trace elements (Fe, Cu, Zn, Mn) (Lindsay and Norvell, 1978).

 

3 Results and Discussion

Soil samples results

Effect of plant population density, nitrogen fertilizer rates and soil depths on soil phosphorus, potassium, calcium, magnesium, manganese, aluminium, copper, iron and zinc are presented in Figures 1 to 9.

 

From the Figure 1, there was significant difference in P with increase in depth (LSD0.05=3.32). Spacing 4X4 exhibited the highest phosphorus content at the rate160 KgNha-1yr-1 and 320 KgNha-1yr-1 across the soil depths. This indicates that different ppd have different abilities to absorb nutrients from the soils and leaching of the elements occur when applied at a higher rate.

 

 

Figure 1 Effect of plant population, nitrogen fertilizer application rates and soil depth on soil P

 

There were significant (p≤0 .05) differences in mean levels of K due to nitrogen fertilizer rates (LSD0.05=12.07) and the four depths (LSD0.05=10.10) (Figure 1). The reason of this situation, with the excess nitrogen fertilizers application to tea plantation, tea plant vegetation and potassium uptake from soil increases, as a result potassium deficiency occurs (Kacar, 1984; Ranganathan and Natesan, 1987). The significant difference with depths is because of the high rate of leaching.

 

There was a significant interaction between the calcium and different nitrogen fertilizer rates (LSD0.05=40.56) and depth (LSD0.05=29.45) (Figure 2) meaning that the responses did not occur in the same pattern.

 

 

Figure 2 Effect of plant population, nitrogen fertilizer application rates and soil depth on soil K

 

There was significant difference in magnesium with both nitrogen fertilizer rates (LSD0.05=5.10) and depth (LSD0.05=3.18) (Figure 3). Plant spacing 2X2 had the highest amount of magnesium across all depths (Figure 4).

 

 

Figure 3 Effect of plant population, nitrogen fertilizer application rates and soil depth on soil calcium

 

 

Figure 4 Effect of plant population, nitrogen fertilizer application rates and soil depth on soil magnesium

 

From the Figure 5, there is significant difference in manganese with depth (LSD0.05=15.95). The amount of manganese is approximately the same in every depth at the rates of 160 KgNha-1yr-1.

 

 

Figure 5 Effect of plant population, nitrogen fertilizer application rates and soil depth on soil manganese

 

The Figure 6 shows that there was significant difference in aluminium with depth (LSD0.05=40.87). The amount of aluminium decreases with increase in depth at fertilizer rates of 320 KgNha-1yr-1. Aluminium content in spacing 2X4 and 3X4 is approximately the same when fertilizer is applied at the rate of 160 KgNha-1yr-1.

 

 

Figure 6 Effect of plant population, nitrogen fertilizer application rates and soil depth on soil aluminium

 

The mean levels of Cu varied with nitrogen rates (Figure 7) due to varied level of Cu supply to the soil.

 

 

Figure 7 Effect of plant population, nitrogen fertilizer application rates and soil depth on soil copper

 

Significant (p≤0.05) differences were observed in Fe levels with depth (LSD0.05=5.90) (Figure 8). There was increase in iron content in every depth with increase in fertilizer rates. This is due to the leaching of the soil content including iron.

 

 

Figure 8 Effect of plant population, nitrogen fertilizer application rates and soil depth on soil iron

 

The mean levels of Zn varied from spacing to spacing (Figure 9) meaning that they have varied abilities to absorb Zn from the soil.

 

 

Figure 9 Effect of plant population, nitrogen fertilizer application rates and soil depth on soil zinc

 

4 Conclusion

The results showed that there were significant difference in many of the elements with population density and nitrogen fertilizer rates (LSD<0.05%). The significant difference with depths was majorly due to the high rate of leaching.

 

Acknowledgements

The authors are very grateful to Kenya Agricultural and Livestock Research Organization (KALRO), Tea Research Institute for fully funding the research.

 

References

Den Braber K., Sato D., and Lee E., 2011, Farm and forestry production and marketing profile for tea (Camellia sinensis), Specialty Crops for Pacific Island Agroforestry, Permanent Agriculture Resources, Hawai, pp.1-33

 

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Owour, P.O., Wanyoko, J. K., and Rutto, J. K., 1995, Effect of plant population and nitrogen fertilizer on yield and quantity of clonal tea. Proceedings of 1995 International quality, Human Health Symposium, China, pp.324-332

 

Suarez, D.L., 1996, Beryllium, Magnesium, Calcium, Strontium and Barium. In: Methods of Soil Analysis: Chemical Methods, Sparks, D.L. (Ed.). Part 3, Soil Science Society of America, Madison, WI., pp.575-603

 

Wanyoko, J.K., Othieno, C.O., Mwakha, E., and Cheruiyot, D.K., 1997. Effect of types and rates of nitrogen fertilizer on leaf nutrients contents of seedling tea in Nandi Hills, Kenya. Tea., 18(1): 21-31

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