Effects of Rate and Timing of Nitrogen Application on Growth and Yield of Seedcane (Saccharum Spp)

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 growerTreatments 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.