Influence of Maternal Season on Field Establishment of Sorghum Varieties Grown in Zimbabwe

Maternal season defined, as the prevailing environmental conditions during crop growth has been known to influence not only grain yield but also seed quality. A laboratory and field experiment were conducted in October 2014, to determine the influence of total rainfall and mean monthly temperature on germination, vigor and emergence of sorghum seeds which were harvested from three different seasons and were kept under controlled conditions. The laboratory experiment was a 3 x 3 factorial experiment laid in completely randomized block design (CRD) replicated three times. The first factor was variety (Macia, SDSL 89473 and Sima), the second factor was growing season (2004/5, 2006/7, 2007/8). A field experiment was carried out to investigate the emergence of seed materials used in the laboratory experiment. The experiment was a 3 x 3 x 3 factorial treatment structure laid out in a Randomized Complete Block Design (RCBD) with the third factor being sowing depth at 5.0, 7.5 and 10.0 cm. Seedling emergence was observed at 10 days after sowing. In the laboratory experiment it was observed that there was no significant difference (P>0.05) on the effects of season and variety on germination of seeds. However, there was significant difference (P<0.001) on seed vigor due to variety under laboratory conditions. For the field experiment, there was significant interaction (P<0.001) on seedling emergence due to season, sowing depth and variety. The highest emergence for all varieties was observed at a sowing depth of 5cm. It can be concluded that maternal season, which is the season in which the seed was grown, has great influence on the vigor of seed produced under dry-land agriculture. There is need to repeat the experiment using more seed lots harvested at many different seasons in order to determine the exact optimum amount of rainfall and temperatures during the maternal season that will promote optimal germination and emergence of dry-land sorghum varieties

Evaluating the effects of chemical ripening with fluazifop-p-butyl on sugarcane (Saccharum officinarum) yield and sugar content

Ripening in sugarcane refers to an increase in sugar content on a fresh weight basis prior to commercial harvesting. Ripening is often prompted by use of chemicals and environmental cues such as moisture stress. The aim of this research was to determine the effects of Fluazifop- pbutyl, a chemical ripener on sugarcane yield and sugar content. The experiment was laid out as a Random Complete Block Design (RCBD) with five replications. Treatments were: Fluazifop- p- butyl (0.45 lha-1), drying off, Fluazifop- p- butyl (0.45 lha-1) + drying off and the control (no Dry off, no Fluazifop- p- butyl). The experiment was carried out at Triangle Estate which is located in the South East Lowveld of Zimbabwe from March 2012 to May 2012. Data on sugarcane yield, sugar quality (Pol % and ERC %) and sugar yield was collected 56 days after establishment of the experiment. Analysis of variance was done on yield and quality data using Genstat 14th edition. Results showed that there were significant differences (P = 0.05) among treatments on sugarcane yield, sugar yield, Pol% and ERC%. The sugarcane yield was highest for the control where no ripener was used. Fluazifop- p- butyl treatment attained 13.9% lower sugarcane yield relative to the control. Application of Fluazifop- p- butyl resulted in the highest sugar yield which was 35.6% higher than that of the control where no ripener was used. A combination of Fluazifop- p- butyl and Dry of resulted in the highest Pol % and highest ERC %. It can be concluded that Fluazifop- p- butyl is effective in increasing sugar yield although it results in a reduction in sugarcane yield. Combining Fluazifop- p- butyl with Dry off results in increased Pol% and ERC%. There is need for further studies to determine the optimum period from spraying Fluazifop- p-butyl to harvesting of sugarcane as this was only done at the end of the drying-off period

Use of linear regression models to estimate missing heat pulse velocity data: a case study in two citrus cultivars

Heat pulse velocity sap flow measurement techniques are considered reliable and accurate for estimating tree water use in woody species. In order to be representative and scalable, probes are typically installed in a number of sample trees and inserted to stratified depths to account for heterogeneity in hydraulic conductivity exhibited by the sapwood. However, during measurement of heat pulse velocities with a large number of probes for an extended period of time, periods of missing data in one or more probes are likely to occur. In this work the effectiveness of using linear regression models between different probe data sets to estimate and patch missing data was evaluated. Hourly heat pulse velocities in two well-irrigated citrus orchards planted with ‘Delta’ Valencia and ‘Bahianinha’ Navel orange trees [Citrus sinensis (L.) Osbeck] were measured using the heat ratio method (HRM). The measurements were conducted in two consecutive seasons at Moosrivier Farm in Groblersdal, which is located in the summer rainfall area of South Africa, as part of a Water Research Commission funded research project on water use of fruit trees. Four trees were sampled in each orchard, each of which had four probes inserted to different depths in the sapwood of the main stem. Two approaches were evaluated for the linear regression models. The first approach was to analyse the relationships between HPV data measured by the different probes. The second approach was to use equations developed between one probe and the average of the other probes in the same orchard at the same time of the day. The regression models were validated by comparing estimated values against independently observed data from the same probe. In both orange tree cultivars sap flow velocities were observed to decrease with increasing sapwood depth, measured from the bark towards the stem centre. This emphasizes the need to use multiple sensors to accurately estimate water use of individual trees when using sap flow measurement techniques. Linear regression models can be used to effectively estimate missing data when long term sap flow measurements using multiple probes are conducted in citrus trees

Assessment of the feasibility of using stalk diameter fluctuations for automated centre pivot irrigation scheduling of sugarcane in Zimbabwe.

The feasibility of a partial automatic irrigation scheduling technique for sugarcane was developed and tested against three independent methods namely: (i) the growers’ current irrigation practice, based on class A-pan measurements, (ii) a climate-based approach using the ZIMsched model irrigation charts and (iii) the modified class A-pan method, using site-specific pan coefficients. The automated scheduling treatment was fitted with a relay to trigger irrigation when soil moisture reached a predetermined threshold. The threshold was determined from analysing diurnal evolution (DE) and maximum daily shrinkage (MDS) of cane stalk measurements using dendrometers. Soil moisture depletion was measured with moisture probes placed in the root zone of the cane and connected to a data logger. Treatment effects were assessed based on the water applied, power used, cane height, and yield. For the three-month period of observation from 16 December 2006 to 18 March 2007, the automated method used 9.2% less water than the growers’ current class A-pan irrigation schedule, while the ZIMsched charts and the modified class A-pan used 22.4% and 10.4% more water than the control, respectively. Automatic scheduling did not reduce the cane yield, while savings on water and power were made. Irrigation efficiency was improved significantly by reducing deep percolation. Dendrometers showed great potential as a tool that can be used for stress monitoring in sugarcane plants, and hence irrigation control

Evaluating the Effects of Chemical Ripening with Fluazifop-p-butyl on Sugarcane (Saccharum officinarum) Yield and Sugar Content

Ripening in sugarcane refers to an increase in sugar content on a fresh weight basis prior to commercial harvesting. Ripening is often prompted by use of chemicals and environmental cues such as moisture stress. The aim of this research was to determine the effects of Fluazifop- p- butyl, a chemical ripener on sugarcane yield and sugar content. The experiment was laid out as a Random Complete Block Design (RCBD) with five replications. Treatments were: Fluazifop- p- butyl (0.45 lha-1), drying off, Fluazifop- p- butyl (0.45 lha-1) + drying off and the control (no Dry off, no Fluazifop- p- butyl). The experiment was carried out at Triangle Estate which is located in the South East Lowveld of Zimbabwe from March 2012 to May 2012. Data on sugarcane yield, sugar quality (Pol % and ERC %) and sugar yield was collected 56 days after establishment of the experiment. Analysis of variance was done on yield and quality data using Genstat 14thedition. Results showed that there were significant differences (P&nbsp;= 0.05) among treatments on sugarcane yield, sugar yield, Pol% and ERC%. The sugarcane yield was highest for the control where no ripener was used. Fluazifop- p- butyl treatment attained 13.9% lower sugarcane yield relative to the control. Application of Fluazifop- p- butyl resulted in the highest sugar yield which was 35.6% higher than that of the control where no ripener was used. A combination of Fluazifop- p- butyl and Dry of resulted in the highest Pol % and highest ERC %. It can be concluded that Fluazifop- p- butyl is effective in increasing sugar yield although it results in a reduction in sugarcane yield. Combining Fluazifop- p- butyl with Dry off results in increased Pol% and ERC%. There is need for further studies to determine the optimum period from spraying Fluazifop- p- butyl to harvesting of sugarcane as this was only done at the end of the drying-off period. &nbsp

Crop coefficient approaches based on fixed estimates of leaf resistance are not appropriate for estimating water use of citrus

The estimation of crop water use is critical for accurate irrigation scheduling and water licenses. However, the direct measurement of crop water use is too expensive and time-consuming to be performed under all possible conditions, which necessitates the use of water use models. The FAO-56 procedure is a simple, convenient and reproducible method, but as canopy cover and height vary greatly among different orchards, crop coefficients may not be readily transferrable from one orchard to another. Allen and Pereira (Irrig Sci 28:17–34, 2009) therefore incorporated a procedure into the FAO-56 approach which estimates crop coefficients based on a physical description of the vegetation and an adjustment for relative crop stomatal control over transpiration. Transpiration crop coefficients derived using this procedure and fixed values for citrus did not provide good estimates of water use in three citrus orchards. However, when mean monthly leaf resistance was taken into account, good agreement was found with measured values. A relationship between monthly reference evapotranspiration and mean leaf resistance provided a means of estimating mean leaf resistance which estimated transpiration crop coefficients with a reasonable degree of accuracy. The use of a dynamic estimate of mean leaf resistance therefore provided reasonable estimates of transpiration in citrus

Germination performance of tobacco varieties in response to different water potentials, priming and post - priming storage durations

Sub optimal seed germination and seedling establishment are major problems in tbacco (Nicotiana tabacum L) transplant production maybe due to dormancy, low soil moisture and poor seed to media contact in the float tray system . Seed priming in which seeds imbibe water or osmotic solutions followed by drying offers rapid germination and uniform seedling establishment

Modelling water use of subtropical fruit crops: the challenges

Subtropical fruit crops form an important part of the fruit industry in many countries. Many of these crops are grown in semi-arid regions or subtropical regions where rainfall is seasonal and as a result the vast majority of these perennial, evergreen orchards are under irrigation. This represents a significant irrigation requirement and with more emphasis being placed on the conservation of water and orchard profitability, it is becoming increasingly important to accurately estimate water use of these crops and schedule irrigation accordingly. The FAO-56 procedure is a simple, convenient and reproducible method for estimating water use. However, the transferability of crop coefficients between different orchards and growing regions is not always readily achieved, due largely to differences in canopy size and management practices. In addition, as subtropical crops tend to exhibit a higher degree of stomatal control over transpiration than most other agricultural crops, some measure of canopy or leaf resistance must be taken into account when using models based on atmospheric demand. The challenge is therefore to provide reliable and dynamic estimates of canopy resistance from relatively simple parameters which can be of use to irrigation consultants and farmers for determining the water requirements of these crops. The challenge remains to ensure that these dynamic estimates are realistic and readily applicable to a number of growing regions. The derivation of transpiration crop coefficients, based on canopy cover and height and a dynamic estimate of leaf resistance, provided reasonable estimates of transpiration in three orchards in contrasting climates, suggesting that this approach could prove useful in future for subtropical crops

The water use of selected fruit tree orchards (volume 2) : technical report on measurement and modelling

Final report to the water research commission and department of agriculture, forestry and fisheries. The water use of selected fruit tree orchards (Volume 2) : technical report on measurements and modelling

Crop coefficient approaches based on fixed estimates of leaf resistance are not appropriate for estimating water use of citrus

The estimation of crop water use is critical for accurate irrigation scheduling and water licenses. However, the direct measurement of crop water use is too expensive and time consuming to be performed under all possible conditions, which necessitates the use of water use models. The FAO-56 procedure is a simple, convenient and reproducible method, but as canopy cover and height vary greatly among different orchards, crop coefficients may not be readily transferrable from one orchard to another. Allen and Pereira (2009) therefore incorporated a procedure into the FAO-56 approach which estimates crop coefficients based on a physical description of the vegetation and an adjustment for relative crop stomatal control over transpiration. Transpiration crop coefficients derived using this procedure and fixed values for citrus, did not provide good estimates of water use in three citrus orchards. However, when mean monthly leaf resistance was taken into account, good agreement was found with measured values. A relationship between monthly reference evapotranspiration and mean leaf resistance provided a means of estimating mean leaf resistance which estimated transpiration crop coefficients with a reasonable degree of accuracy. The use of a dynamic estimate of mean leaf resistance therefore provided reasonable estimates of transpiration in citrus.South Africa‟s Water Research Commission (Project K5/1770, Water use of fruit tree orchards), with cofounding from the South African National Department of Agriculture, Forestry and Fisheries.http://link.springer.com/journal/2712016-12-30hb201