3.1 Description of experimental site
The study was carried out at Midlands State University main campus which is situated ten kilometres south-east of the Midlands provincial capital Gweru the third largest city in Zimbabwe at an altitude of 1424 m above sea level. It lies in Natural Region 3and receives a mean annual rainfall 500-750 mm, which normally falls from November to March. Geographically the site is found at latitude19.4847° S, longitude 29.8365° E. Average temperature in summer and winter are 21.5and 12.8 respectively.
The area has brown, medium grained sand clay loam soils of granite origin and resembles those conducive for quinoa production across the world. They are slightly acidic with a pH of about 5.7 and the study site was a west facing slope which is better exposed to the sun.
3.2 Experimental design
The experiment was conducted as a Randomized Complete Block design (RCBD) with three blocks. Five different nitrogen levels at N1=0 kg ha-1 AN, N2= 30 kg ha-1 AN, N3= 60 kg ha-1 AN, N4 = 90 kg ha-1 AN and N5=120 kg ha-1 AN were allocated to plots using Ammonium Nitrate fertiliser as treatments.
Nitrogen was split applied with the first half dose of nitrogen fertiliser Ammonium Nitrate (NH4NO3) applied during planting as well as equal measurement of basal fertiliser Compound L Fertiliser 700-800 kg/ha was applied in the plots because of its considerable P2O5 content and the rest of nitrogen was applied three weeks after emergence as Ammonium Nitrate (NH4NO3).
3.3 Soil characteristics
Before carrying out the trials, random soil samples from the experimental site were carried out to a depth of 0-20 cm through the Z- sampling process and all the samples were mixed together to form a composite sample and brought to the laboratory for analysis. Chemical and Mechanical analysis of the soil was done to determine the chemical and physical. Below is a table showing soil chemical and physical components of the soil that was analysed.
Table 2 Soil physical and chemical properties
Colour Texture PH Available
P2O5 Potassium Calcium Magnesium
B MgSCL 5.7 375 0.44 10.98 5.66
Where B = Brown
MgSCL= Medium grained Sand Clay Loam
3.4 Experimental procedures
3.4.1 Land preparation
Tillage was done to a depth of 10cm using a mattock on a piece of land measuring 212.5 m2on the 15th of February 2019. The land was then harrowed using a hand harrow to remove unwanted vegetation and in order to obtain a fine tilth. The land was divided into three blocks (A, B, C) each block consisting of five plots. Each plot constructed under an area of 6m2 had boarder ridges which allowed increased water retention within the plots. The height of the plot boarder ridges was 20cm.
3.4.2 Planting of Quinoa
As a very small seed quinoa was planted in furrows using the drilling method at seed rate of 15kg per hectare. Each plot consisted of three furrows that where spaced with an interline spacing of 50 cm. Fertiliser application was done to the respective treatments. Fertiliser was applied using the drilling method. After seeds were sown, top soil of 3cm was put on top of the furrows to cover the seed.
3.4.3 Fertilization in the field
Compound L (4N:17P:11K) was applied as a basal fertiliser during planting at a rate of 750kg per hectare because of its considerable P2O5 content. Compound L was applied at equal measurement in all plots.
Ammonium Nitrate (34.5% N) was split applied with the first half dose applied during planting and the last dose of the nitrogen fertiliser applied as top dressing three weeks after emergence. Ammonium Nitrate (34.5% N) rate was determined per treatment under the following levels N1=0 kg ha-1, N2 =30 kg ha-1, N3=60 kg ha-1, N4 =90 kg ha-1, and N5 = 120 kg ha-1. Under these treatments, N1 was the control which received 0 kg ha-1 of Ammonium Nitrate per plot. For other treatments of Ammonium Nitrate (34.5% N), N2 received 52.17 per plot, N3 received 104,34g per plot, N4 received 156.51g per plot and N5 received 208.68g per plot. With total Ammonium Nitrate (34.5% N) of the experimental field recorded at 2086g.
Land was kept weed-free starting from a week after emergence and hand hoeing was done 2weeks after emergence since the crop cannot tolerate weeds. No herbicide was applied at any stage of plants growth. Weeds were removed from time to time using hand pulling in order to keep the plots weed free.
Thinning was done using hands 2 weeks after emergence .This was done to a standard of 10cm in row spacing and a plant population of 200 000 plants per hectare. Thinning was done in order to reduce plant to plant nutrient completion.
Watering was done using a hose-pipe irrigation system at three days intervals. Watering was done so as to enhance nutrient absorption from the soil and also facilitating photosynthesis and end product conveyance to various plant parts.
3.5 Data collection
Height was measured from the ground level to the tip of the plant on the main stem. Measurements were taken with a meter ruler starting from two weeks after emergence and measurement continued at weekly intervals. The plants assessed were the same plants that were tagged for leaf area. In each plot four plants were randomly tagged and used in the assessment of plant height. Height was measured in centimetres (cm).
3.5.2 Number of leaves
This parameter was measured by counting the number of leaves on the plant starting from two weeks after emergence and counting continued at weekly intervals. The plants assessed were the same plants that were tagged for leaf area and plant height. In each plot four plants were randomly tagged and used to assess on the number of leaves.
3.5.3 Leaf Area
Leaf length and leaf width of quinoa plants were obtained and used to calculate leaf area per plot. A metre rule was used to measure both the leaf length and leaf width. Two weeks after emergence leaf area measurements were taken and the measurement continued at weekly intervals. The plants that were assessed were tagged to allow more data to be collected as well as for consistence measurements. In each plot four leaves from different plants were assessed and measurements were taken. The overall experimental plot was 25 metres by 8.5 metres giving a total plot size of 212.5m2. The leaf area was calculated using this formula:
Leaf Area (cm2)
= length of leaf (cm) ? width of leaf (cm)
3.5.4 Number of shoots
This parameter was measured by counting the number of shoots on the plant starting from two weeks after emergence and counting continued at weekly intervals. The plants assessed were the same plants that were tagged plant height, number of leaves and leaf area. In each plot four plants were randomly tagged and used to assess on the number of leaves.
3.5.5 Leaf area index
Starting one month after emergence, plants were sampled at weekly intervals to determine Leaf Area Index (LAI). A non- destructive method was used to measure LAI where Leaf Area was measured using a tape measure and expressed on per ground area basis. Ten plants per plot were randomly tagged and used to assess the Leaf area and the number of leaves per plant. Leaf Area Index was expressed in the formula given below.
LAI= LA/ GA
Where LAI = Leaf Area Index= Leaf Area/ Ground Area.
3.5.6 Data analysis
One way analysis of variance (ANOVA) was done using GenStat 18th edition to analyse data from the treatments. The separation of means was done using Fishers Protected LSD at 5% level of significance.