ABSTRACT
Nitrogen (N) is among the most important crop nutrient. Numerous metabolic activities, particularly those involved with crop growth, such as tillering and stalk elongation, rely on N. N deficiency reduces light interception and photosynthesis due to a reduction in leaf area, chlorophyll synthesis, and biomass production. Many intensive agricultural production systems, such as sugarcane systems, which collect a large quantity of biomass, necessitate higher N rates. N recommendations, on the other hand, should use an application rate that minimizes environmental impact while maintaining greater yields. This is accomplished by using the appropriate rate of N at the appropriate moment. Several studies have found that the optimum N treatment rate is affected by a variety of parameters, including soil type, crop age, plant and soil characteristics, climate, growing cycle length, and growing season duration. The influence of N rate and time of N-rate on growth and yield of two phenologically distinct sugarcane varieties is investigated in this study. Two experiments were conducted simultaneously at the Sugar Research Institute (SRI) of the Kenya Agricultural and Livestock Research Organization (KALRO) in Kibos (KALRO-SRI-Kibos) and at the Nucleus Section of Mumias Sugar Factory (MMS NE-Mumias) from October 2018 to July 2019. The design used was a RCBD with a 3 x 2 x 3 factorial arrangement of the treatments with three replications. The net plot size for data collection was 1.5 m x 2 rows x 5 m = 15 m2 in nucleus estate and 1.2 m x 2 rows x 5 m = 12 m2 in out grower Treatments included two varieties (KEN 82-216 and KEN 82- 601), three N rates of 0, 60 and 120 kg N/ha supplied as fertilizer Urea (46 % N), and three timings of N application, which included one-time application at three months after planting (T1), two-equal split applications at three and six months after planting (T2), and a delayed one-time application at six months after planting (T3). Data was collected on percent seedling emergence, plant height, number of leaves per plant, internode length, stem girth, leaf area index, stalk population and cane yield. The two varieties recorded a significance difference (P≤0.05) in number of tillers in both Mumias and Kibos. At Mumias, interactions between variety and N-rate, resulted in a significant effect in leaf area index in the 5th month. At Mumias, N-rates significantly affected the number of leaves per plant in the 10th month. Variety KEN 82-601 recorded a higher average height of (91cm) than variety KEN 82-216 (81 cm) in Kibos and Mumias respectively. A significant effect of N-rates on plant height between the varieties was recorded in the 7th and 10th months and N-rates and varietal interactions recorded a significant effect on stalk height in Mumias in the 5th and 7th month. At Kibos, the two varieties recorded a higher average dry mass of 415w/m2 compared to 348w/m2 recorded at Mumias. Nitrogen-rate recorded a significant effect on plant population in Mumias. Increase in N-rate resulted to a high plants/ha of 10151 at 120 kg/ha at Mumias compared to 8153 plant/ha in the control. There was no difference in yield at Kibos and Mumias in variety KEN 82-216. N-rate of 120 kg/ha resulted in high seed yield of 25 t/ha compared to 19 t/ha under control, and 23 t/ha for 60 kg/ha N. Mumias recorded a higher seed yield of 22.5 t/ha compared to Kibos at 20 t/ha. Time of N-rate application recorded a significant effect on leaf area index in the 3rd month at Kibos while at Mumias, non-significant effect of time of N-rate application on leaf areas index were recorded. N-rate application in the 6th month after planting (T3) recorded a higher internode length than T1 and T2, while in Mumias, N-rate application in the 3rd month after planting recorded a higher average length of 17cm compared to T2 (16.9 cm) and T3 (16 cm). Varieties grown at Mumias recorded a higher average number of leaves of 44 per plant compared to those grown at Kibos which recorded 40 leaves per plant. A high average number of leaves were recorded in the 7th month at Mumias (58leaves) and Kibos (50leaves). N-rate application at the 3rd month after planting (T1) recorded a higher stem girth of 2.4 cm compared to T2 (2.2 cm) and T3 (2.3 cm) in Kibos. A higher average plant height was recorded at T3 (N-rate application 6 months after planting) in Kibos (94.6 cm) and Mumias (89 cm). Interactions between varieties and time of N application had non-significant effect on number of tillers in Kibos and Mumias. Variety KEN 82-216, recorded a higher average plants/ha of 9225 than variety KEN 82-601 that recorded an average of 7714 plants per hectare. N-rate application at T3 (6 months after planting) recorded the highest dry weight of 467 w/m2. From this study, it can be concluded that 120 kg of N applied in splits at 3rd and 6th months after planting may be suitable for seedcane production as they recorded high seedcane yield of 29 t/ha and better agronomic performance. Variety KEN 82-216 had a better response to N application, and thus it could be practiced in N- intensive farms.
TABLE OF CONTENTS
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABBREVIATIONS AND ACRONYMS v
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xiii
ABSTRACT xv
CHAPTER ONE: GENERAL INTRODUCTION
1.1 Background 1
1.2 Statement of the problem 2
1.3 Justification of the study 3
1.4 Objectives 5
1.5 Hypotheses 5
CHAPTER TWO: LITERATURE REVIEW
2.1 Botany and ecology of sugarcane 6
2.2 Climatic requirements for sugarcane production 6
2.3 Sugarcane production trends in Kenya 6
2.3.1 Evolution of the sugar iIndustry in Kenya 6
2.3.2 Breeding of sugarcane in Kenya 7
2.3.3 Sugar Production 8
2.4 Constraints to sugarcane production in Kenya 8
2.5 Crop protection and agronomic practices 10
2.6 Phenology and physiology of sugarcane 10
2.7 Germination 11
2.7.1 Tillering 11
2.7.2 Stem elongation 11
2.7.3 Ripening 11
2.7.4 Sugarcane flowering 12
2.8 Nitrogen nutrition in sugarcane 12
2.8.1 Nitrogen use efficiency 12
2.9 Yield formation in sugarcane 14
2.9.1 Biomass accumulation 14
2.9.2 Radiation interception and use efficiency 14
2.9.3 Sucrose metabolism 14
2.10 Timing of nitrogen supply on growth and yield 15
CHAPTER THREE: EFFECT OF NITROGEN RATE ON GROWTH AND YIELD OF TWO PHENOLOGICALLY CONTRASTING SUGARCANE VARIETIES
3.1 Abstract 16
3.2 Introduction 17
3.3 Materials and methods 17
3.3.1 Experimental site description 17
3.3.2 Treatments and experiment design 18
3.3.3 Experiment management 18
3.4 Data collection 19
3.4.1 Crop growth traits 19
3.4.2 Yield components 20
3.5 Data analysis 20
3.6 Results 20
3.6.1 Soil chemical properties 20
3.6.2 Weather data during the crop season and crop phenology 21
3.6.3 Set establishment 22
3.6.4 Tillering 23
3.6.5 Leaf chlorophyll content 24
3.6.6 Leaf count 26
3.6.7 Leaf area index 28
3.6.8 Stalk height 30
3.6.9 Dry weight 32
3.6.10 Inter-node length 34
3.6.11 Stalk girth 36
3.6.12 Plant population 37
3.6.13 Seedcane yield (t/ha) 39
3.7 Discussion 40
3.8 Conclusion 43
CHAPTER 4: EFFECT OF TIMING OF NITROGEN APPLICATION ON GROWTH AND YIELD OF TWO PHENOLOGICALLY CONTRASTING SUGARCANE
VARIETIES
4.1 Abstract 44
4.2 Introduction 45
4.3.1 Treatments and experiment design 46
4.3.2 Experimental layout, design and crop husbandry 47
4.4 Data collection 47
4.4.1 Crop growth traits 47
4.4.2 Yield components 48
4.5 Data analysis 48
4.6 Results 48
4.6.1 Germination percentage 48
4.6.2 Effect of time of nitrogen application on Leaf area index (LAI) (m/m2) of seedcane varieties 49
4.6.3 Effect of time of nitrogen application on chlorophyll content of selected seedcane varieties 51
4.6.4 Effect of time of nitrogen application on the internode length (cm) of selected seedcane varieties 53
4.6.5 Effect of time of nitrogen application on number of leaves per plant of selected seedcane varieties 55
4.6.6 Effect of time of nitrogen application on stalk girth (cm) of selected seedcane varieties 56
4.6.7 Effect of time of nitrogen application on plant height (cm) of selected seedcane varieties 58
4.6.8 Effect of time of nitrogen application on number of tillers of selected seedcane varieties 60
4.6.9 Effect of time of nitrogen application on the number of plants/ha of selected seedcane varieties 62
4.6.10 Effect of time of nitrogen application on dry weight per plant of selected seedcane varieties 64
4.6.11 Effect of time of nitrogen application on sugarcane yield (t/ha) of selected sugarcane varieties 65
4.7 Discussion 67
4.7.1 Crop phenology and growth 67
4.7.2 Leaf area and leaf greenness 67
4.7.3 Yield components and yield 68
4.8 Conclusion 69
CHAPTER 5: GENERAL DISCUSSION, CONCLUSIONS AND RECOMMENDATIONS
5.1 General discussion 70
5.2 Conclusions 72
5.3 Recommendations 72
REFERENCES 73
APPENDICES 83
Appendix: Pictures 83
LIST OF TABLES
Table 1. Sugar factories establishment in Kenya and their capacities in 2015 and 2016 ... 7
Table 2. Soil chemical properties of Mumias and Sugar Research Institute in Kibos 21
Table 3. Mean monthly maximum (MaxT) and minimum (MinT) temperature and rainfall during the experimental season from August 2018 and August 2019 in Mumias and Kibos. 22
Table 4. Variety and N interaction effects on number of tillers/m2 at different months after planting (MAP) in Kibos and Mumias 24
Table 5. Variety and nitrogen (N) interaction effects on chlorophyll nm/m2 at different months after planting (MAP) in Kibos and Mumias 26
Table 7. Variety and nitrogen (N) interaction effects on number of leaves at different months after planting (MAP) in Kibos and Mumias 28
Table 6. Variety and nitrogen (N) interaction effects on leaf area index(m2) at different months after planting (MAP) in Kibos and Mumias 30
Table 8. Variety and nitrogen (N) interaction effects on height at different months after planting (MAP) in Kibos and Mumias 32
Table 9. Variety and nitrogen (N) interaction effects on dry weight (w/m) at different months after planting (MAP) in Kibos and Mumias 34
Table 10. Variety and nitrogen (N) interaction effects on internode cm/m2 at 9th and 10th months after planting (MAP) in Kibos and Mumias 35
Table 11. Variety and nitrogen (N) interaction effects on stalk girth cm/m2 in different months after planting (MAP) in Kibos and Mumias 37
Table 12. Variety and nitrogen (N) interaction effects on plant population/m2 in 10th months after planting (MAP) in Kibos and Mumias 38
Table 13. Variety and nitrogen (N) interaction effects on yield t/ha in 10th months after planting (MAP) in Kibos and Mumias 40
Table 14. Germination percentage of two selected seedcane varieties at 30 and 45 days after planting 49
Table 15. Time and nitrogen (N) effect on leaf area index(m/m2) at different months after planting (MAP) in Kibos and Mumias 50
Table 16. Time and nitrogen (N) interaction effects on leaf area index m/m2 at different months after planting (MAP) in Kibos and Mumias 51
Table 17. Time and nitrogen (N) effect on chlorophyll nm/m2 at different months after planting (MAP) in Kibos and Mumias 52
Table 18. Time and nitrogen (N) N interaction effects on chlophylly nm/m2 at different months after planting (MAP) in Kibos and Mumias 53
Table 19. Time and nitrogen (N) effect on internode/m2 at different months after planting (MAP) in Kibos and Mumias 54
Table 20. Time and nitrogen (N) interaction effects on internode at 9 and 10th months after planting (MAP) in Kibos and Mumias 54
Table 21. Time and nitrogen (N) effect on number of leaves per plant at different months after planting (MAP) in Kibos and Mumias 55
Table 22. Time and nitrogen (N) interaction effects on chlophylly nm/m2 at different months after planting (MAP) in Kibos and Mumias 56
Table 23. Time of nitrogen (N) and verieties interaction effects on stem girth (cm) in Kibos and Mumias 57
Table 24. Time and nitrogen (N) interaction effects on plant hieght(cm) at different months after planting (MAP) in Kibos and Mumias 60
Table 25. Time and nitrogen (N) effects on number of tillers (cm) at different months after planting (MAP) in Kibos and Mumias 61
Table 26. Time of nitrogen (N) and variety interaction effects on number of tillers at different months after planting (MAP) in Kibos and Mumias 62
Table 27. Time of nitrogen (N) and variety interaction effects on number of tillers in 10th month in Kibos and Mumias 63
Table 28. Time of nitrogen (N) and variety interaction effects on dry weight (w/m2) at different months after planting (MAP) in Kibos and Mumias 65
Table 29. Time of nitrogen (N) and variety interaction effects on seedcane yield (t/ha) 10th month in Kibos and Mumias 66
LIST OF FIGURES
Figure1. Germination percentage of sugarcane at Kibos (a) and Mumias (b) respectively. Bars are standard error of mean………………… 222
Figure 2. Average number of tillers/m2 for variety KEN82-601 and KEN82-216 at Kibos (a) and Mumias (b), and effect of N rate on average number of tillers at Kibos (c) and Mumiasndard… 23
Figure 3. Average percentage of chlorophyll nm/m2 for variety KEN82-601 and KEN82- 216 at Kibos (a) and Mumias (b), and effect of N rate on chlorophyll at Kibos (c) and Mumias 25
Fugure 4. Average leaf area index/m2 for variety KEN82-601 and KEN82-216 at Kibos
(a) and Mumias (b), and effect of N rate on average leaf area index at Kibos (c) and Mumias 29
Figure 5. Average number of leaves/m2 for variety KEN82-601 and KEN82-216 at Kibos (a) and Mumias (b), and effect of N rate on on average number of leaves at Kibos (c) and Mumias… 31
Figure 7. Average dry weight (w/m2) for variety KEN82-601 and KEN82-216 at Kibos (a) and Mumias (b), and effect of N rate on on average dry weight (w/m2) at Kibos (c) and Mumias 33
Figure 8. Average internode /m2 for variety KEN82-601 and KEN82-216 at Kibos (a) and Mumias (b), and effect of N rate on on average internode at Kibos (c) and Mumias (d) 35
Figure 9. Average stalk gith /m2 for variety KEN82-601 and KEN82-216 at Kibos (a) and Mumias (b), and effect of N rate on on stalk gith at Kibos (c) and Mumias (d).………36
Figure 10. Average stalk population /m2 for variety KEN82-601 and KEN82-216 at Kibos (a) and Mumias (b), and effect of N rate on stalk population at Kibos (c) and Mumias (d) 38
Figure 11. Average yield t/ha for variety KEN82-601 and KEN82-216 at Kibos (a) and Mumias (b), and effect of N rate on yield t/ha at Kibos (c) and Mumias (d).…39
Figure 12. Average stem girth (cm) for variety KEN82-601 and KEN82-216 at Kibos (a) and Mumias (b), and effect of time of N rate on stem girth (cm) at Kibos (c) and Mumias (d) 57
Figure 13. Average plant height (cm) at Kibos (a) and Mumias (b), and effect of time of N rate on height (cm) at Kibos (c) and Mumias (d) 59
Figure 14. Average dry weight (w/m2) at Kibos (a) and Mumias (b) and effect of time of N rate on dry mass (w/m2) at Kibos (c) and Mumias (d) on the varieties… 63
Figure 15. Average dry weight (w/m2) at Kibos (a) and Mumias (b) and effect of time of N rate on dry weight (w/m2) at Kibos (c) and Mumias (d) on the varieties 64
Figure 16. Average seedcane yield (t/ha) at Kibos (a) and Mumias (b) and effect of time of N rate on seedcane (t/ha) at Kibos (c) and Mumias (d) on the varieties 66
ABBREVIATIONS AND ACRONYMS
BMPs Best Management Practices
C Carbon
DAP Diammonium Phosphate
FAO Food and Agricultural Organization
FRG Farmers Research Group
FRI Fractional Radiation Interception
GDP Gross Domestic Product
Ha Hectare
K Potassium
KALRO Kenya Agricultural and Livestock Research Organization
KESREF Kenya Sugar Research Foundation
KNA Kenya National Assembly
KSA Kenya Sugar Authority
KSB Kenya Sugar Board
LAI Leaf Area Index
LM Lower Midland
LSD Least Significant Difference
LTM Long term mean
MMS Mumias Sugar
NAE Nitrogen Agronomic Efficiency
NE Nucleus Estate
NPE Nitrogen Physiological Efficiency
NPK Nitrogen Phosphorous Potassium
NRE Nitrogen Recovery Efficiency
NUE Nutrient Use Efficiency
OG Out-growers
pH Log [H+]
N Nitrogen
PPM Parts per Million
RCBD Randomized complete block design
RUE Radiation Use Efficiency
SPAD Soil Plant Analysis Development
SRI Sugar Research Institute
SSP Single Super Phosphate
TCH Tonnes Cane per Hectare
WV Weight by Volume
CHAPTER ONE
GENERAL INTRODUCTION
1.1 Background
According to global sugar production statistics for 2020/2021, Brazil was the world's largest sugar- producing country, producing approximately 42 million metric tonnes of sugar. During that time, global sugar production was approximately 179 million metric tons (Shahbandeh, 2021) with Africa accounting for 5.8%. East Africa is a net importer of sugar, with production in 2011/12 totaling 1,018,572 MT versus consumption of 1,501,477 MT (Lichts, 2012). Kenya has approximately 202,000 ha of sugarcane production, with an average production of 5.262 million tonnes of cane being supplied to factories per year. Furthermore, average sugarcane yields have fallen from around 66.4 t/ha in 2015 to 55 t/ha in 2018 which are significantly lower than the global average of 63 t/ha (Mati and Thomas, 2019). Low quality sugarcane varieties, poor agronomic management, high input costs, delayed harvesting, and industry disillusionment are among the reasons for productivity decline (Mati and Thomas, 2019).
The sugar industry is important in the agricultural sector, employing approximately 6 million Kenyans both directly and indirectly (Boniface et al., 2017). Sugar production is a major contributor to the economy and has led to approximately 16% growth to the nation’s Gross Domestic Product .The sub sector despite of having greater contribution to the country its output rate is declining and for now it is at 65 tonnes per hectare comparing with the approximated average national output of 100 tonnes per hectare (Ambetsa et al.,2020)
Nitrogen is essential for healthy vegetative growth and crop development (Sreewarome et al., 2007). It is a very difficult nutrient to manage when fertilizing sugarcane because it interacts with organic matter in the soil and can be lost in a variety of ways (Cantarella and Rossetto, 2014). Cane requires a high N fertilizer nutrient to produce biomass (Bohnet et al., 2011). N is accumulated in stalks, with the above ground parts of the cane plant containing approximately 0.7 to 1.6 kg of N per ton of stalk and the entire plant requiring approximately 2 to 2.4 kg of N per ton of stalk. During harvesting, cane extracts containing more than 200 kg N/ha yielding 100 t/ha of stalks and 90 to 110 kg/ha are exported (Cantarella and Rossetto, 2014). However, excessive or insufficient uptake causes stunting by reducing photosynthesis. N nutrition affects yield by increasing sucrose accumulation in harvested cane, but the rate of varietal response to N application varies (Wood, 1990).
Little is known about how nitrogen rate and timing of application influences establishment and yields of seed cane crop in Kenyan sugar industry (Achieng et al.,2015) In addition, N by genotype interaction are only partially understood in seedcane crop but it is more understood in millable cane. Sugarcane cultivars are completely different in their performance, quality and yield due to their genetic variation (Pereira et al., 2017).
Phenology is elongation and growth development of sugarcane in relation to environment, most important temperature (Keller, 2010). It contributes to yields and crop adaptation of crop to different environments (Khan and Iqbal, 2007). In sugarcane as in most cereal crops phenology is strongly related to temperature and time recurring physiology of the crop and its surrounding environment interaction during the development stages (Dendrobium and Orchidaceae, 2012). Phenology and leaf area development influence biomass accumulation (Andrade et al., 2016). In turn, biomass accumulation determines the amount of radiation intercepted and sucrose metabolism (Andrade and Bertini, 2006).
The relationship between Kenya’s sugarcane hybrids temperature is only partially understood (Lingle, 1999). Temperature impacts the development stages, biomass accumulation and sugar levels in plant parts as well as enzymatic activity in sucrose metabolism. Sugarcane plants growing under constant temperature of 15oC had slow crop growth rate and few leaves as well as few and short internodes (Ebrahim et al.,1998; Lingle, 1999). In addition, at 45o C, tiller production is reduced when the crop is already developed and elongated. It was found that leaf senesced early under 45°C compared with 15oC (Ebrahim et al., 1998). Sucrose concentration was also found to be higher in plants under 15°C and lower in 45°C. The Mediterranean climate of high temperature resulted in shorter internodes and lower sucrose content than crops under lower temperature (Shnghera et al., 2019)
1.2 Statement of the problem
Higher cane and sugar output is based on the selection of high-yielding varieties and adequate crop management, including the administration of balanced fertilizer at the appropriate rate and time. Nitrogen is necessary for plant growth. Adequate nitrogen availability to crops is known to increase photosynthetic activity, vigour in vegetative development, and dark green color in plant leaves Boddey, (1995). Nitrogen is the nutrient that has the most impact on how sugarcane grows and how much it produces (Clements, 1980). Climate, crop age, growth cycle length, plant traits, and soil factors all influence global N recommendations for sugarcane production (Wiedenfeld, 1995). Low sugarcane yields in Kenya are mostly related to poor N fertilizer management, among other issues. Unfortunately, fertilizer prices are exceedingly expensive all around the world.
Given that N fertilizer is mostly applied below the soil surface (8–10 cm) on sugarcane farms, ammonia volatilisation is nolonger considered a major issue. However, N losses through denitrification, leaching and runoff are still of great concern as sugarcane farms are mostly located in area with high rainfall more than 1200 mm/year (Wang et al., 2016). Nitrogen-efficient management strategies are needed to mitigate N2O emissions from sugarcane farming while maintaining productivity and profitability.The apparent recovery of applied nitrogen by plants is rarely more than 50 percent, while the remainder is lost from the soil plant system (Whitfield, 1992), improved management practices can aid in nitrogen uptake efficiency.
Nitrogen deficiency in Western Kenya has contributed to low and declining sugarcane yields, as well as poor application timing. Environmental factors affect productivity of varieties with even high yielding potential resulting in low yields. Technologies such as agronomic practices, sugar processing technologies, market research, and technology dissemination revolve around the improved sugarcane variety. A comparative analysis of sugarcane productivity in terms of establishment and yield at various rates and times of nitrogen fertilizer application is required.
1.3 Justification of the study
It is critical to manage nitrogen application in order to maximize cane yield and obtain sugar recovery. Early N application may reduce total cane tonnage, whereas delayed application will result in delayed maturity and decreased sugar accumulation. According to Reghenzani et al., (1996), timing N application to coincide with conditions optimum for plant uptake can positively influence N uptake. With increased public concern about environmental quality, high production costs, and low nitrogen fertilizer use efficiency (NUE) (20-40%, (Vallis and Keating, 1994, Gava et al., 2005, Meyer et al., 2007), it is vital to enhance N management in sugarcane production. However, the N requirement of cane to produce maximum production differs between fielads and cropping years. Several studies have demonstrated that sugarcane does not typically respond to N fertilizer because there is enough mineralized Nitrogen available during the fallow period (Muchovej and Newman, 2004, Lofton and Tubaa, 2015). According to Wiedenfeld (1995), an overabundance of plant-available N could explain the increased quantity of immature stalks later in sugarcane growth (Salter and Bonnett, 2000). The higher quantity of immature stalks at harvest can dilute cane sugar, resulting in lower sucrose content and economic value. Inadequate N at tillering (rapid stalk formation), on the other hand, eventually lowered overall sugarcane biomass production due to decreased canopy photosynthesis and sugarcane's inability to sustain growth later in the season.
Studies (Meyer et al., 2007; Perez and Melgar, 1998) have shown that crop response to nitrogen fertilization is varied and complex, and often linked to availability of nitrogen held in soil organic matter. Correct N nutrition not only increases cane yield, but also improves the sucrose content in the harvested cane. This response to N rate varies with variety , region, temperature, number of sunny days and watering regime.
Several studies have documented the use of plant N response to enhance techniques of estimating crop N requirements based on chlorophyll readings (Peterson et al., 1993, Varvel et al., 1997). Lofton et al., (2012) discovered that the Normalized Difference Vegetation Index (NDVI) measured by an active canopy reflectance sensor during the late tillering stage of sugarcane may be utilized to evaluate the sugar production response to increased N fertilizer in sugarcane. However, unlike the widely studied Normalized Difference Vegetation Index (NDVI), the timing of N-rate application is not well documented. The study's objectives were to improve sugarcane production and quality by better regulating nitrogen through optimal N-rates and timing of N-application. This study's findings are applicable to crop management and variety selection (Robinson et al., 2007). As a result, it is critical to understand how the timing and amount of N applied affects sugarcane growth and yields.
1.4 Objectives
The broad objective of this study is to improve the yield of seedcane through better management of nitrogen supply.
This study has been conceived with the following specific objectives:
(i) To determine the effect of the rate of N application on growth and yield of two phenologically contrasting seedcane varieties
(ii) To determine the effect of timing of N application on growth and yield of two phenologically contrasting seedcane varieties
1.5 Hypotheses
(i) Sugarcane responds to increased nitrogen rate, irrespective of variety.
(ii) Timely nitrogen application improves sugarcane yield.
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