MSCAGR (Soil Science) / Department of Soil Science / The application of organic manures as alternatives to reduce the use of mineral fertilizers is
considered a good agricultural practice for smallholder farmers. However, the effect of organic
manure on soil properties and crop yield depends upon its application rate and chemical
composition. Climatic seasonal variability within the study area could adversely affect crop
production. The amount of rainfall and temperature are among the most important factors that
determines crop production. This field experiment was carried out during the 2013/2014 and
2014/2015 cropping seasons at the University of Venda experimental farm which is located
about 2 km west of Thohoyandou town in the Vhembe District, Limpopo Province.
The main objective of this study was to determine the effect of three types of organic manure
(cattle, poultry and their combination (1:1)) on yield and water use efficiency of sunflower
(Helianthus annuus L.) and selected soil physical and chemical properties under rainfed
conditions. The experiment was a randomized complete block design (RCBD) with four
treatments and four replications (control (C0), cattle manure (CM), poultry manure (PM) and
their combination (CM + PM)). All organic manures were applied 21 days before planting at a
rate equivalent to 20 t ha-1. The manures were incorporated in the soil using a hoe to an
approximate depth of 10 cm.
Crop water use (WU) and water use efficiency (WUE) were determined using the water balance
equation. Rainfall was measured using three standard rain gauges installed on the experimental
site. Change in soil moisture storage was determined by monitoring soil moisture content
weekly using a neutron water meter (NWM), calibrated on the experimental site.
Data on sunflower dry matter and leaf area index (LAI) was collected at flower bud stage,
flowering stage and at grain maturity stage. Plant height and stem girth were also determined at
the same developmental stages. Grain yield was measured at physiological maturity.
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Analysis of variance (ANOVA) was carried out using SPSS software. Due to seasonal variability
encountered during the two cropping seasons, particularly in terms of rainfall, further analysis of
two factors (viz. cropping season and organic manure) and their interaction were performed.
The differences between treatment means were separated using the least significant differences
(LSD) procedure.
The results showed that organic manure application had no significant effect on soil physical
properties. Poultry manure application resulted in lowest bulk density (BD) with a decrease of
32% in the top layer (0 – 20 cm) compared to control. Cattle manure + PM and CM application
decreased BD in the top layer by 14% and 9% compared to control, respectively. Poultry
manure and CM recorded almost the highest similar stable aggregate fractions at all soil depths.
Poultry manure recorded the highest final infiltration rate and cumulative infiltration followed by
CM and CM + PM. The control treatment retained the highest mean water content compared to
other treatments at both field capacity (FC) and wilting point (WP). Cattle manure + PM and PM
recorded the least mean water content among others at FC and WP respectively. This could be
as a result of increased micropores by organic manure application on a clayey soil which
allowed an ease movement of water that control treatment which had no manure application.
Total N, Ca, and Zn were significantly different between treatments in the first cropping season
while K, Na, CEC and Zn were significantly different in second cropping season. pH recorded no
significant difference in all treatments in both cropping seasons. CM + PM recorded the highest
OC at top layer (0 – 20 cm) in both cropping seasons compared to other treatments.
Dry matter yield and LAI at flower bud, flowering and maturity stages increased with the
application of different manures compared to the C0. Organic manure application showed a
significant (p<0.05) effect on dry matter at all growth stages in the second cropping season.
Organic manure had a significant effect on LAI only at flower bud stage of the first cropping
season, with PM and CM + PM recording the highest similar value of 1.31. The manure
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application also showed a significant (P<0.05) effect on plant height and stem girth at all
growing stages in the second cropping season, whereas in the first cropping season the
significant effect was only in the flower bud stage for both parameters.
Grain yield was significantly affected by the manure application in the second cropping season.
Manure application in the second cropping season resulted in an increase in the grain yield
compared to the first cropping season, except for PM where the grain yield decreased
significantly by 167.92% from the first cropping season. Then high grain yield in the second
cropping season could be as a result of high WUE reported.
The manure application had a significant effect (p<0.05) on water use efficiency (WUE) in the
second cropping season. The WUE recorded the highest values under CM and CM + PM
treatments in second cropping season than in first cropping season, while PM recorded the
highest WUE value in the first cropping season. Generally, organic manures used obtained
higher grain yield and WUE compared to control.
Keywords: Organic manure, smallholder farmers, sunflower and water use efficiency
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:univen/oai:univendspace.univen.ac.za:11602/615 |
| Date | January 2016 |
| Creators | Mokgolo, Matome Josphinos |
| Contributors | Mzezewa, J., Mzezewa, J., Odhiambo, J. J. O. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | 1 online resources (xii, 105 leaves : color illustrations) |
| Rights | University of Venda |
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