| Crop rotational effects on irrigated winter and summer grain crops at Vaalharts | Nel, A.A. | 2011 |
KeywordsBarley, canola, groundnut, maize, wheat AbstractThe beneficial effect of crop rotation on yield is well known on annual dryland cropping while knowledge is lacking on the rotational effect in short cycle cropping with two annual irrigated crops. Canola, barley and wheat were rotated with groundnut, maize and soybean in 10 different rotation systems of one and two year cycle lengths over four years in a field trial at Vaalharts. Maize crown and root rot intensity and associated pathogens were identified during the fourth year of the trial. Compared to barley and wheat, canola as preceding crop suppressed yields of maize and groundnut by 10% and 13%, respectively. Groundnut, canola and wheat yields were affected by a season x crop system interaction. Barley yields were unaffected by crop rotation. Contrary to expectation, summer crop yields in some one-year systems were not different from those of the two-year systems, indicating that one-year crop systems can be sustainable, provided that two matching crops namely maize and barley in rotation, and wheat and groundnuts in rotation are grown. Maize root rot ratings correlated well (r =−0.80) with maize grain yield. Fungi most frequently isolated from maize crowns were Fusarium oxysporum and Trichoderma spp. and from roots were F. equiseti, F. oxysporum, F. solani, Pyrenochaeta terrestris and Trichoderma spp. AuthorsNel, A.A. and Lamprecht, S.C. Year Published2011 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2011.10640023 This article contributed by:
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| A rapid demonstration of the self-thinning rule using radish | Smith, F.R. | 2011 |
KeywordsIntraspecific competition, plant density, plant mass, power rule, Raphanus sativa AbstractThe self-thinning rule describes the relationship between individual mass and density in crowded evenly-aged plant populations in which the slope of the relationship is always greater than -1. This study investigated whether the rule could be demonstrated in six weeks using radish (Raphanus sativa L.) grown in trays (0.033 m2) in a greenhouse. Seeds of a radish cultivar were sown in a 4:2:1 mixture of sand, potting soil and compost and watered twice daily to field capacity. One week later, seedlings in each tray were thinned out to one of 19 densities ranging from 4 to 64 individuals. Thereafter, the radishes were left to grow for a further five weeks under the same watering regime and then harvested. The log-log regression of average fresh mass against density produced a slope of −0.76 which deviates significantly from the expected −4/3 power rule. This result indicates that initial plant densities need to be higher if the self-thinning rule is to be demonstrated successfully. AuthorsSmith, F.R. Year Published2011 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2011.10640024 This article contributed by:
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| Macro and micro element requirements of young and bearing apple trees under drip fertigation | Kangueehi, Grace
N. | 2011 |
Keywordsnutrient fixation, nutrient loss, nutrient solutions, orchard nutrition, phenological stage, yield Abstract‘Brookfield Gala’ apple trees on Merton 793 rootstock were planted on a loam sand soil at 2000 trees ha−1, trained to a central leader using the solaxe system and supplied with nutrients by drip fertigation. Trees were individually excavated at successive phenological stages in growth seasons two and three, and divided into structural components which were dried, weighed, and analysed to determine their macro and micro nutrient element concentrations. Losses in fruit, leaf drop and pruning were calculated, as were transfers to the permanent structure (fixation). To offset losses and fixation, second season trees needed to take up N, P, K, Ca, Mg and S at 34.5, 3.7, 23.8, 23.9, 5.8 and 1.8 g tree−1, respectively. Respective requirements for Mn, Fe, Cu, Zn, B and Mo were 118, 541, 18.1, 92.8, 79.4 and 2.1 mg tree−1. For third season trees producing 45.2 t ha−1, mineral requirements were within the ranges: N, 1.7–2.6; P, 0.3–0.4; K, 2.3–3.3; Ca, 0.5–1.9; Mg, 0.2–0.4; S, 0.2–0.2; Mn, 1.3–7.9; Fe, 28.7–32.6; Cu, 0.9–1.1; Zn, 3.0–5.5; B, 5.7–7.6 and Mo, 0.3–0.3 mg kg−1 yield. AuthorsKangueehi, Grace
N., Stassen, P.J.C., Theron, K.I. and Wooldridge, J. Year Published2011 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2011.10640025 This article contributed by:
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| Field evaluation of Ugandan sweetpotato germplasm for yield, dry matter and disease resistance | Yada, B. | 2011 |
KeywordsAlternaria bataticola, blight, Ipomoea batatas, specific gravity, SPVD AbstractA total of 946 morphologically distinct accessions of sweet-potato (Ipomoea batatas [L.] Lam) germplasm collected from Uganda were evaluated along with four released cultivars for root yield, dry matter, sweetpotato virus disease (SPVD) and Alternaria bataticola blight disease resistance for two seasons; 2005B (September 2005 to January 2006) and 2006A (April to August 2006) at three sites for selection of superior genotypes. The genotypes differed significantly in yield, dry matter content, SPVD and Alternaria blight resistance (p=0.05). Genotype SPVD severity ranged from 1.0 to 5.0 with an overall mean of 2.6. Alternaria severity scores ranged from 1.0 to 5.0 with an overall mean of 2.2. Total root yields ranged from 0.0 to 52.5 t ha−1 with an overall average of 20.3 t ha−1. Most genotypes had mean total root yields of less than 15.0 t ha−1, low specific gravity values of less than 2.0, and low disease resistance. A positive correlation was observed between SPVD and Alternaria blight (r=0.33), while both diseases were negatively correlated with yield traits. A total of 192 superior genotypes were selected for further evaluation and use for variety development in hybridization schemes. AuthorsYada, B., Tukamuhabwa, P., Alajo, A. and Mwanga, R.O.M. Year Published2011 PublicationSouth African Journal of Plant and Soil Locations- Soroti, Eastern Region, Uganda (1.715, 33.6111)
- Kumi, Eastern Region, Uganda (1.4856, 33.9332)
- Pallisa, Eastern Region, Uganda (1.1675, 33.71)
- Arua, Northern Region, Uganda (3.03, 30.91)
- Lira, Northern Region, Uganda (2.2489, 32.9)
- Luwero, Central Region, Uganda (0.8331, 32.4994)
- Kabale, Western Region, Uganda (-1.25, 29.99)
- Mbarara, Western Region, Uganda (-0.6057, 30.6486)
- Kabarole, Western Region, Uganda (0.5851, 30.2513)
DOI10.1080/02571862.2011.10640026 This article contributed by:
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| Effects of relay inter-cropping summer cover crops with maize on cover crop biomass and maize yields in a warm-temperate region of South Africa | Murungu, F.S. | 2011 |
KeywordsConservation agriculture, C/N ratio, mucuna, sorghum, sunhemp AbstractLittle research attention has been given to growing summer cover crops as part of conservation agriculture systems. Three cover crops (sorghum [Sorghum bicolor], mucuna [Mucuna pruriens] and sunhemp [Crotalaria juncea]) were relay-intercropped into maize [Zea mays] 42 days after planting maize. Biomass yields, N uptake and maize yield were measured. In sole cropping, sorghum had the highest dry weight (11 t ha−1) followed by sunhemp (7.2 t ha−1) and mucuna (6.1 t ha−1). However, cover crop biomass yields dropped significantly (85% for sorghum, 70% for sunhemp and mucuna) when relay-intercropped into maize. Nitrogen uptake followed a similar pattern with mucuna having the highest N-uptake of 70 kg N ha−1 in relay-intercropping as compared to the > 250 kg N ha−1 in the sole cropping system. Maize biomass and grain yields were not affected by relay-intercropping cover crops. The low cover crop biomass yields in relay-intercropping may not be viable for sustainable conservation agriculture. AuthorsMurungu, F.S., Chiduza, C. and Muchaonyerwa, P. Year Published2011 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2011.10640027 This article contributed by:
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| Effect of soil fertility management strategies and resource-endowment on spatial soil fertility gradients, plant nutrient uptake and maize growth at two smallholder areas, north-western Zimbabwe | Nyamangara, J. | 2011 |
KeywordsHomefields, outfields, semi—arid conditions, greenhouse experiments AbstractAbstract We investigate the effects of smallholder farmer resource—endowment and soil nutrient management strategies on plant nutrient uptake and growth across soil fertility gradients under semi-arid conditions. Soil fertility gradients as influenced by farmers’ resource availability may affect the response of crops to fertilizer addition and therefore productivity. The study was conducted in Njelele and Nemangwe smallholder areas (450-800 mm per annum, unimodal) in north-western Zimbabwe. Soil and maize cobleaf samples were collected from fields of farmers (varying resource endowment) located near to (homefields) and far away (outfields) from the farmers’ homesteads during the 2005–6 season. The samples were analysed for selected soil fertility indicators and soil samples were further used to test maize growth response to various nutrient applications under greenhouse conditions. Soil fertility (organic C, total N and available P) significantly (P<0.05) decreased from resource-endowed to resource-constrained farmers, and from outfields to homefields, but the latter differences were only significant for available P. Besides resource-endowment and field type, response to nutrient applications also depended on soil texture. In sandy soil, both N and P were limiting to MAIZE growth in outfields while N was most limiting in the homefield. It was concluded that resource-endowment and nutrient resource management strategies employed by farmers result in soil fertility gradients which affect response of crops to fertilisation and therefore need to be factored in the development of fertiliser recommendations. AuthorsNyamangara, J., Makarimayi, E., Masvaya, E.N., Zingore, S. and Delve, R.J. Year Published2011 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2011.10640006 This article contributed by:
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| Seasonal and varietal effects on tiller population development of sugarcane (Saccharum Officinarum L.) | Zhou, M.M. | 2011 |
KeywordsPeak tiller population, thermal time per tiller, tiller survival rate, final tiller population, tiller survival rate AbstractAbstract Tillers carry leaves, determine leaf area index and indirectly influence the amount of photosynthetically active radiation (PAR) intercepted by the sugarcane canopy. Tillers develop into stalks, the sink for the products of photosynthesis. The objective of this study was to investigate the effects of seasons and varieties on tiller population development trends and parameters using different varieties (ZN6, ZN7, N14 and NCo376). Three replicated experiments were established in early (March), mid (July) and late (October) seasons at Zimbabwe Sugar Association Experiment Station. The tiller population development parameters were determined in each plot and the data were analysed for seasonal and varietal effects using the mixed procedure of SAS. The tiller development parameters investigated were: peak tiller population (PTP), final tiller population (FTP), thermal time to peak tiller population (TTTP), thermal time per tiller (TTPT) and tiller survival rate (TSR). The order of importance of the parameters was season > variety > variety x season. The study suggested the presence of genotype by environment (GxE) interaction for PTP. The cane yield of the varieties significantly (P mid > late season. AuthorsZhou, M.M. and Shoko, M.D. Year Published2011 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2011.10640007 This article contributed by:
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| Proximate composition of carob cultivars growing in South Africa | Sigge, G.O. | 2011 |
KeywordsAlternative food source, Ceratonia siliqua, composition, proximate AbstractAbstract Five carob (Ceratonia siliqua L.) cultivars grown in South Africa were analysed for proximate and polyphenol composition as well as for mineral, amino and fatty acid content. Carob pods from the five cultivars were obtained from two locations in the Western Cape Province, South Africa. The average proximate composition (determined using standardised methods) range of raw carob pods was: 8.17 – 9.56% moisture; 40.69 – 54.74% sugars; 29.88 – 36.07% dietary fibre; 3.07 – 4.42% protein; 2.58 – 3.08% polyphenols; 0.45 – 0.86% fat; and 2.13 – 2.69% ash. A total of 17 amino acids were detected, including the seven essential amino acids. All cul-tivars analysed were found to be of good nutritional quality in terms of long-chain fatty acid proportions, i.e. PUFA: SFA and n−6: n−3 ratios. Slight, but statistically significant, compositional variations were found among cultivars. The results obtained in this study suggest that the locally grown carob cultivars are highly nutritious and can thus be considered as an alternative food source in South Africa. AuthorsSigge, G.O., lipumbu, L. and Britz, T.J. Year Published2011 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2011.10640008 This article contributed by:
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| The effect of poor quality seed and various levels of grading factors on the germination, emergence and yield of wheat | Barnard, A. | 2011 |
KeywordsFalling number, hectoliter mass, preharvest sprouting, protein content AbstractAbstract High quality seed is essential for establishing productive stands of wheat. Seed should have, amongst others, a high germination percentage, be free of seed borne diseases and should not contain any weed seed. Protein content (PC), hectolitre mass (HLM) and falling nudmber (FN) are three important quality characteristics determining the grading of wheat at delivery point. Seed with high and low values of these three quality requirements were planted over a two year period under dryland and irrigation conditions to determine the effect of these quality parameters on the yield of the following crop. Seed with various levels of preharvest sprouting damage were also planted to determine the effect of sprouting on the field performance of the crop. Results from this study showed that germination was not affected by grading factors, but the emergence of seed with low HLM was significantly reduced compared to high HLM seed. Low PC had a significant effect on the crop, especially under dryland conditions, while FN did not have an effect. Severely sprouted seed had a significant negative effect on the emergence and yield, especially when seeds were carried over to the next planting season. However, a low intensity of sprouting did not affect the yield negatively. End results indicated that using low quality seed for planting can have a negative effect on crop yield. It is concluded that producers should use certified seed that is true to variety, is clean and has a high germination percentage for crop production. AuthorsBarnard, A. and Calitz, F.J. Year Published2011 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2011.10640009 This article contributed by:
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| Soil aggregate properties and total available water as affected by sugar cane (Saccharum hybrid sp.) production in Mauritius | Cheong, L.R.
Ng | 2011 |
KeywordsMechanized practices, organic matter, soil structure, sugar cane AbstractAbstract Concerns within the sugar industry of Mauritius with respect to soil degradation caused by sugar cane cropping have led to a study on soil quality. As part of this study, the effects of sugar cane production, i.e. cropping and adoption of mechanized practices, on aggregate size distribution, aggregate stability and total available water were investigated for the five major soil groups of Mauritius. These three parameters are indicative of the status of soil structure. Aggregate size distribution was determined by dry sieving, aggregate stability was derived from soil moisture characteristic curves of weathered and unweathered soil samples, and total available water was determined using ceramic pressure plate and cellulose membrane techniques. The results showed that, in general, neither soil structure nor total available water were degraded following the introduction of the sugar cane crop and the subsequent implementation of mechanized practices. A significant increase in aggregate size was observed with cropping in a rocky soil from the sub-humid zone, possibly because of changes in rooting density, with higher biomass being produced under irrigated conditions. On the other hand, aggregates were smaller in soils from the humid to super-humid zones, probably because of a lower organic matter content. Adoption of mechanized practices could also have impacted positively on aggregate properties through soil consolidation under harvester traffic. Aggregate stability decreased significantly with the adoption of mechanized practices only in the Low Humic Latosol, which has the lowest natural organic matter content. In this case, organic matter content could have been depleted with cropping below a critical threshold level. No significant difference was observed in terms of total available water. It can be concluded that sugar cane cropping has not degraded soil structure in the major soils of Mauritius but care should be taken to minimize organic matter depletion when adopting mechanized practices in the Low Humic Latosol. AuthorsCheong, L.R.
Ng, Kee Kwong, K.F.
Ng and Preez, C.c.
Du Year Published2011 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2011.10640010 This article contributed by:
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