Ratoon Cycle Research Articles

English

The sugar and alcohol sector has invested heavily in technologies to increase the productivity of sugarcane and consequently the gross income of sugar and alcohol; among these practices irrigation and fertilization stands out. The objective of this study is to evaluate the agro industrial and sugarcane yield (plant cane and first ratoon cycle) grown in the Sudoeste Goiano, Brazil, as affected by water replacement and nitrogen (N) rates; and to evaluate the residual effect from N rates on sugarcane ratoon grown under water replacement levels. The study was carried out with pots filled with a mixture of 120 kg of Oxisol (Rhodic Hapludox) and cattle manure, in a proportion of 3:1 v/v, respectively. A completely randomized design was used, 3x4, with three repetitions, analyzed in split plots. The treatments were combinations of three levels of replacement water (75, 50 and 25% of available water) and four N rates (0, 60, 120 and 180 kg ha-1, equivalent to pots), which were also the same doses for the treatment residual N rate. In both cycles, at harvesting the stem yield and the total recoverable sugar (TRS) were determined for calculation of gross income of sugar and alcohol. The plant cane was not affected significantly by any of the factors evaluated. Interactions between the residual N doses and water replacements influenced the TRS and the gross income of sugar and alcohol in ratoon cane, proving that the N applied on a cycle can be leveraged by another; the stem productivity was affected only by water replacements.   Key words: Residual nitrogen, sugar yield, alcohol yield, irrigation, stem productivity.

Enhanced-Efficiency Fertilizers in Nitrous Oxide Emissions from Urea Applied to Sugarcane

The environmental benefits of producing biofuels from sugarcane have been questioned due to greenhouse gas emissions during the biomass production stage, especially nitrous oxide (NO) associated with nitrogen (N) fertilization. The objective of this work was to evaluate the use of nitrification inhibitors (NIs) dicyandiamide (DCD) and 3,4 dimethylpyrazole phosphate (DMPP) and a controlled-release fertilizer (CRF) to reduce NO emissions from urea, applied at a rate of 120 kg ha of N. Two field experiments in ratoon cycle sugarcane were performed in Brazil. The treatments were (i) no N (control), (ii) urea, (iii) urea+DCD, (iv) urea+DMPP, and (v) CRF. Measurements of NO fluxes were performed using static chambers with four replications. The measurements were conducted three times per week during the first 3 mo and biweekly afterward for a total of 217 and 382 d in the first and second seasons, respectively. The cumulative NO-N emissions in the first ratoon cycle were 1098 g ha in the control treatment and 1924 g ha with urea (0.7% of the total N applied). Addition of NIs to urea reduced NO emissions by more than 90%, which did not differ from those of the plots without N. The CRF treatment showed NO emissions no different from those of urea. The results were similar in the second ratoon: the treatment with urea showed NO emissions of 0.75% of N applied N. Application of NIs resulted in a strong reduction in NO emissions, but CRF increased emissions compared with urea. We therefore conclude that both NIs can be options for mitigation of greenhouse gas emission in sugarcane used for bioenergy.

Contribution of fertilizer nitrogen to the total nitrogen extracted by sugarcane under Brazilian field conditions

With the ordinance that prohibits sugarcane harvesting with prior burning of plantations in Brazil, sugarcane crops absorbs barely 20 % of the N-fertilizer applied. This low recovery is attributed, in part, to nitrogen (N) mineralization in plant straw, high microbial immobilization, and N losses in the soil-plant system, mainly, when sources containing urea are applied to the soil surface. To evaluate N contribution from fertilizer in the sugarcane compartments and total N extracted by plants during the first ratoon cycle, microplots were installed inside plots of sugarcane ratoons. We applied isotope 15N-labelled urea, ammonium sulfate and ammonium chloride (3 % 15N atoms) at the dose of 100 kg N ha−1. The soil in the study was classified as a Typic-Hapludox and the experimental design consisted of randomized complete block with four replicates. In addition nitrogen immobilization and mineralization rates was evaluated estimated by aerobic incubation during 20 weeks. Sugarcane residue was incorporated to soil and nitrogenous fertilizers applied to the surface as ammoniacal or amidic-N at 100 mg N kg−1. N sources showed the same efficiency as the results showed no difference for N contents in plant shoots obtained from treatment with N fertilization. The use of ammonium chloride resulted in greater accumulation of N fertilizer in stalks at 218 days after fertilization. The percentage of N fertilizer was approximately 60 % in the early developmental stages, decreasing to 20 % near the harvesting stage. The addition of N-fertilizer in soils covered by sugarcane residue leads to immobilization of available-N in the soil.

Nutrient leaching in an Ultisol cultivated with sugarcane

Solute leaching below the crop-rooting zone represents not only a valuable loss of nutrients for the plant, but also a potential pollution source of groundwater. The objective of this work was to quantify nutrient-leaching losses at 0.9m depth in an Ultisol that was cultivated with sugarcane, located in the county of Jaboticabal-SP, Brazil. The following ions were evaluated: nitrite, nitrate, ammonium, sulfate, phosphate, calcium, magnesium and potassium. The first ratoon cycle was monitored from November 16, 2006, to July 9, 2007. The experimental design was organized as four random blocks and three treatments: T1: without fertilizer; T2: 100kgha−1 of N and 114kgha−1 of S; and T3: 150kgha−1 of N and 172kgha−1 of S. To determine the fate of the N-fertilizer and S-fertilizer, four microplots were installed, in which 2.15% atoms of 15N- and 10.5% atoms of 34S-enriched ammonium sulfate were applied. The input and output of anions and cations were quantified from the flux density of water and the ion concentration. The NO3−, K+, Mg2+ and Ca2+ concentrations in the soil increased in January following both rainfall and drainage. The leaching of N was between 3.9 and 34.9kgha−1. The N leached derived from the 100kgha−1 applied N fertilizer was 22.5kgha−1. The S leached was between 4.6 and 8.4kgha−1. From the 114kgha−1 S applied as fertilizer the leaching was 0.480kgha−1. The maximum leaching of P, K, Ca, and Mg were 1.2, 53.6, 135.7 and 39.8kgha−1, respectively. From the results, it is not possible to determine whether the local groundwater will be contaminated, but caution should be taken to maintain soil quality by reducing the leaching loss of nutrients.

Changes in total soil organic carbon stocks and carbon fractions in sugarcane systems as affected by tillage and trash management in Queensland, Australia

The use of sugarcane trash (tops and residue) retention systems has been reported to lead to increases in total soil organic carbon (TOC) stocks. However, these increases have generally been small and confined to the top 0.05 m of the soil profile. It has been hypothesised that the amount of TOC sequestered could be increased if the intensive tillage that occurs at the end of a sugarcane ratoon cycle, which is known to decrease TOC, could be eliminated. This research examined the effect of no-till management and/or trash retention on four trial sites throughout Queensland, to assess the ability of this management to increase TOC stocks. Management effects on particulate organic carbon (POC), humus organic carbon (HOC), and resistant organic carbon (ROC) stocks were also assessed using mid-infrared spectroscopy. No significant changes in TOC, POC, HOC, or ROC were observed over either 0–0.1 or 0–0.3 m depth at any of the sites examined, when sites were considered as a whole. The results indicate that these management practices currently have limited capacity to increase TOC stocks on these soil types over 0–0.1 or 0–0.3 m depth for the purposes of carbon sequestration.

Agroindustrial Evaluation of Sugarcane Varieties in the Central Zone of Veracruz, Mexico

The use of sugarcane varieties having high agroindustrial production, that are resistant to primary pests and diseases and are well adapted to regional conditions is a key factor for increasing the yield of this crop. The objective of this study was to agronomically and industrially evaluate a set of 12 sugarcane varieties in terms of their planting and ratoon cycles. This investigation used methodological protocols developed by the Instituto para el Mejoramiento de la Produccion de Azucar (IMPA) (Institute for the Improvement of Sugarcane Production) to assess the agroindustrial potential of new varieties. The 12 varieties were evaluated by testing them under the same management and climate conditions. An experimental design of completely randomized blocks and three replicates was used. Yield (t ha -1 ) and sucrose content (%) were assessed. There were no significant differences for yield (p > 0.05) with regard to planting cycle. Control variety Q-96 had the highest sucrose content (15.95%). For the ratoon cycle, the highest yield corresponded to variety L 73-65 with 178 t ha -1 , and the lowest value was for variety HA 64-20 having 107 t ha -1 . Variety Mex 91-662 had the greatest sucrose content (17.66%) and its yield (171 t ha -1 ) shows that this variety has great promise for the sugarcane zone supplying the El Modelo refinery and for the state of Veracruz.

Soil attributes and leaf nitrogen estimating sugar cane quality parameters: Brix, pol and fibre

The area of sugar cane production in Brazil has substantially increased in the last few years due to the high demand for ethanol. It is estimated that the actual area, which is approximately 8 Mha, will increase to as much as 15 Mha in the next 10 years. In addition to enlarging the boundaries and installing new industrial units, sugar cane expansion demands better use of production areas and improvement of both yield and quality, combined with a reduction of production costs. Thus, models that can describe the behaviour of sugar cane quality parameters could be important in understanding the effects of soil and plant attributes on these parameters. The objective of this work was to fit mathematical models to the sugar cane Brix, pol and fibre parameters using physical soil attributes, chemical soil attributes and leaf nitrogen as predictors from the previous year. This work was carried out in an area of 10 ha located in Araras, SP, Brazil, from November 2008 until July 2011 in the first (plant cane), second (first ratoon) and third (second ratoon) cycles of the crop. The chemical soil attributes analysed were the macronutrients and micronutrients, and the soil physical attribute analysed was the soil texture. The variables used in the models were chosen using principal component analysis (PCA), and the fit of the models was made as the mean of multiple regressions. The results were compared using kriging to map the Brix, pol and fibre with the true and estimated values. The Brix, pol and fibre models presented R 2 values of 0.17, 0.06 and 0.18, respectively, for the first ratoon of the crop and 0.23, 0.19 and 0.52, respectively, for the second ratoon. These results allowed the estimation of Brix, pol and fibre with estimation errors less than 1 % for the first and second ratoons. The PCA approach identified soil organic matter, phosphorus and potassium as the soil attributes that had the higher variance of the dataset during the years studied.

Biometria da parte aérea da cana soca irrigada no Submédio do Vale do São Francisco

A produtividade da cana-de-açúcar no Submédio do Vale do São Francisco tem apresentado desempenho de destaque devido à utilização de irrigação. Dessa forma, a obtenção de informações sobre o crescimento das plantas nessas condições é essencial, uma vez que podem ser utilizados para adequação do manejo da cultura. Assim, objetivou-se com este trabalho realizar uma análise biométrica da parte aérea da cana-de-açúcar irrigada, visando suprir a ausência de informações desta cultura na região. O experimento foi realizado no município de Juazeiro-BA, com a variedade RB92579, no ciclo de cana soca. Realizaram-se dois tipos de análise, sendo uma destrutiva, onde plantas foram amostradas e conduzidas ao laboratório, e outra de natureza não destrutiva, na qual as variáveis foram monitoradas em campo. A partir dos resultados, foi possível constatar que a cultura apresentou altos padrões de perfilhamento (15,2 perfilhos m-2). O tombamento da cana-de-açúcar afeta a dinâmica da estatura dos colmos, a qual atingiu valor final de 421 ± 22 cm. Porém, não demonstrou impactos diretos sobre os padrões de comprimento (13,6 ± 2,4 cm), diâmetro (2,5 ± 0,2 cm) e volume dos internódios (68,8 ± 19,5 cm³), bem como no rendimento. A taxa de aparecimento foliar foi de 0,0079 folhasºCd-1, no Intervalo I, e de 0,0018 folhas ºCd-1, no Intervalo II. A área máxima da folha (423 ± 39 cm²) depende da sua posição no colmo (nº15) e responde, principalmente, ao comprimento foliar (máximo valor de 146 ± 6 cm), logo que a largura máxima (~4,2 ± 0,2 cm) tende a se estabilizar ao longo do ciclo. O índice de área foliar apresentou uma correlação positiva com o número de folhas verdes abertas e com a área das folhas.

Composição bromatológica da cana-de-açúcar como forrageira em função da altura de corte e da época de colheita

This work was undertaken to evaluate the relationship between sugarcane (Saccharum spp.) culms basal cutting height and harvest period and their effects on bromatologic characteristics of two sugarcane cultivars under ratoon cycle. The research was carried out in the region of Jaú, SP, Brazil. The experiment was arranged in randomized blocks, in a 2 x 3 x 3 factorial design corresponding to two genotypes (IAC86-2480 and RB72454), three cutting heights (0, 10 and 20 cm above soil level) and three harvest periods (May, July and September 2006) with four replications. The results of the interaction between cultivar x cutting height x harvest period showed that sugarcane cultivars had better forage quality in terms of dry matter and crude protein by the cutting height at 0 and 10 cm and harvest period of the culms in September, and in terms of mineral matter, neutral detergent fiber, acid detergent fiber and lignin when the harvest season was in May. The cultivar IAC86-2480 has better chemical quality as forage, since the cutting height of the stalks is adjusted to the period of harvest.

Produtividade e qualidade da cana-de-açúcar irrigada com efluente de estação de tratamento de esgoto

O objetivo deste trabalho foi avaliar o desempenho produtivo e qualitativo da cana-de-açúcar (Saccharum spp.), irrigada por gotejamento subsuperficial com efluente de estação de tratamento de esgoto (EETE). Testaram-se lâminas de irrigação entre 0, na testemunha sem irrigação, e 200% da evapotranspiração máxima da cultura, em dois ciclos de cultivo de cana soca, adubada com metade da quantidade recomendada de nitrogênio (N). A produtividade, em cada ciclo, foi ajustada a um modelo que considera a produtividade da cana planta como covariável. Por esse modelo, os ganhos em produtividade, proporcionados pela reposição da evapotranspiração com EETE, foram de 17,13 e 25,76 Mg ha-1. A aplicação de 200% de EETE resultou no ganho estimado de 19,84 Mg ha-1 na primeira soca e 40,47 Mg ha-1 na segunda. Houve redução de sólidos solúveis do caldo da cana, com o uso da irrigação na primeira soca. No entanto, outros parâmetros indicativos da qualidade industrial não foram significativamente alterados pela irrigação. A irrigação com EETE proporciona ganhos de produtividade da cana-de-açúcar e reduz a adubação nitrogenada recomendada no cultivo da primeira e segunda socas.

Stability and adaptability of early maturing sugarcane clones by AMMI analysis

Stability and adaptability of 14 early maturing sugarcane clones were evaluated at 11 locations in the State of Parana, in the plant cane and ratoon cycles, by the AMMI method. By AMMI2, 59.44% cumulative variance was explained in plant cane and 54.22% in ratoon cane by the first two principal components of tons of pol per hectare (TPH). For genotype RB966928 the TPH was medium to high, phenotypic stability high and adaptability general, recommending this early maturing clone with wide adaptability for northern Parana. The genotype-environment interaction was lowest in Paranavai and Mandaguacu (most stable locations), where the ranking of genotypes was more reliable than the means of the environments tested.

Removal of bunch, leaves, or pseudostem alone, or in combination, influences growth and bunch weight of ratoon crops in two banana cultivars

SummaryWe manipulated the source (leaf system) and sink (bunch) in banana cultivars ‘Williams’ and ‘Grand Nain’ to determine the effect on two subsequent ratoon cycles. Ratoon growth and bunch characteristics were measured on plants, in a plantation, that were treated in two seasons: one warm and sunny season, and the other cool and cloudy. Removing bunches or leaves affected growth of the ratoon in the first 3 months after treatment, and this effect differed between seasons. Defoliating bunched plants in the warm and sunny season caused the first ratoon crop to bunch 5.1 weeks earlier than those on intact plants. Defoliation in both seasons reduced the height and bunch size of ratoon plants, especially in ‘Williams’. Bunch removal in the cool and cloudy season reduced the cycle time by 2.5 weeks. The bunch is a higher priority C-sink than the ratoon, and there is an indication that floral induction in banana plants is influenced by environmental conditions independently of internal plant effects.

Urea and sugarcane straw nitrogen balance in a soil-sugarcane crop system

The objectives of this study were to evaluate nitrogen utilization by sugarcane ratoon from two sources, applied urea and sugarcane straw covering soil surface (trash blanket), besides the recovery of N from both sources in the soil-plant system. The following treatments were established in a randomized block design with four replicates: T1, vinasse-urea (100 kg ha-1 of urea-N) mixture applied on the total area of the soil covered with cane trash labeled with 15N; T2, vinasse-urea mixture (urea labeled with 15N; 100 kg ha-1 of urea-N) applied on the total area of the soil covered with non-labeled sugarcane trash; and T3, urea-15N (100 kg ha-1 of urea-N) applied in furrows at both sides of cane rows, with previous surface application of vinasse, onto soil without trash covering. The vinasse was applied at a rate of 100 m³ ha-1 in all treatments. The experiment was carried out on a Yellow Red Podzolic soil (Paleudalf), from October 1997 to August 1998, in Piracicaba, SP, Brazil. The nitrogen use efficiency of urea by the sugarcane ratoon was 21%, while that of the sugarcane straw was 9%. The main contributions of N from sugarcane trash, during one cycle, are the preservation and increase of the organic N in soil. The tendency for a lower accumulation of urea-N in the sugarcane plant, in the soil surface covered with sugarcane residue, was compensated by the assimilation of N from trash mineralization. Nitrogen derived from cane trash was more available to plants in the second half of the ratoon cycle

Post-ratoon growth and yield of three hybrid papayas (Carica papaya L.) under mulched and bare-ground conditions

At Yarwun (151.3°E, 23.75°S), a trial was conducted to compare 3 papaya hybrids (Hybrid 29, Hybrid 11 and Hybrid 13) under mulching with grass hay or in bare ground. The viability of ratooning a papaya crop was also investigated. After a 16-month cropping season plants were cut to a 750-mm stump (ratooned) about monthly over a 3.5-month period and, following a 4.5-month regrowth period, were harvested for a period of 11 months (post-ratoon). Hybrid 29 yielded (by weight) 54% more than Hybrid 11 and 92% more than Hybrid 13 during the 3.5-month ratooning period. At the commencement of ratooning, Hybrid 29 plants were 41–58 cm shorter than Hybrid 11 and 13 plants, allowing the Hybrid 29 plants to be retained for longer before being ratooned. Hybrid 29 also returned to fruiting more quickly with a greater proportion of plants (97%) with fruit at the first post-ratoon harvest compared with Hybrid 11 (87%). Following regrowth (post-ratoon) the 3 hybrids produced similar yields. All 3 hybrids were equally susceptible to the 3 phytoplasma diseases and to nematodes. The plots mulched with coarse grass hay yielded 70% more during the ratooning period and 116% more post-ratoon than the plots with bare ground. This difference was attributed in part to fewer root-knot nematodes, the roots being more heavily infected with vesicular arbuscular mycorrhiza, the use of the complete upper soil profile by the roots, reduced rainfall run off and less soil loss in the mulched treatment. The highest yielding treatment, mulched Hybrid 29, averaged the equivalent of 55 t/ha.year during ratooning, 43 t/ha.year over the 11-month post-ratoon harvest period and 65 t/ha.year over the entire plant–ratoon cycle. These yields were achieved in spite of drought conditions and quite severe outbreaks of the phytoplasma diseases, dieback, yellow crinkle and mosaic, with 60% of plant positions infected with dieback during the post-ratoon period. Theoretical yield estimations using the data from the plant and post-ratoon crops indicated that ratooning may give superior average monthly yields compared with 2 successive plant crops because of the reduced time required for the ratooned crop to return to production. The study demonstrated the benefits of mulching, the superiority of Hybrid 29 and that ratooning may be successfully used in papaya. In environments similar to Yarwun, Hybrid 29, or similar hybrids, with mulching is recommended for commercial production. If land, time or finances are limiting, consideration should be given to ratooning the plant crop based on monthly cut outs over a 3–4-month ratooning period with vacant plant positions replanted during ratooning.

The impact of Pineapple mealybug wilt-associated virus-1 and reduced irrigation on pineapple yield

The impacts of Pineapple mealybug wilt-associated virus-1 (PMWaV-1) and reduced irrigation on pineapple fruit yield in plant and ratoon crops were evaluated in a field experiment in Hawaii. In the plant crop, PMWaV-1 infection and reduced irrigation had no significant effects on fruit weight. In the ratoon crop, plants infected with PMWaV-1 produced smaller fruit than disease-free plants and plants that received reduced irrigation also produced smaller fruit than plants that received regular irrigation. Additive effects of PMWaV-1 infection and reduced irrigation were detected; plots of infected plants that received reduced irrigation produced the fewest fruit. Frequency distributions for fruit size in the ratoon cycle showed shifts to smaller sized fruit classes when PMWaV-1 or reduced irrigation were present. Estimated yield from combined plant and ratoon crops for infected plants was 6.7% less than disease-free plants when plants received regular irrigation. Reduced irrigation correlated with a 4.2% reduction in estimated yield of disease-free plants, and both infection and irrigation reduction together reduced yield 13.4%. These results show that PMWaV-1 and reduced irrigation can have a negative and additive impact on pineapple fruit production in the first ratoon.

AMMI and Stability Analyses of Bunch Mass in Multilocational Testing of Musa Germplasm in Sub-Saharan Africa

There is a genuine need within a plantain and banana (Musa spp.) breeding program to assess thoroughly the experimental materials through a sequence of trials. This will result in the selection of promising clones as potential new cultivars in the targeted agroecozone. Stability analyses and the additive main effects and multiplicative interaction (AMMI) model provide together a means for the identification of clones with 1) homeostatic responses to environmental changes, 2) a genotypic response to environmental changes, and 3) adaptation to specific niches. Fourteen polyploid clones (10 tetraploid hybrids and 4 triploid cultivars) were evaluated in a broad range of environments in sub-Saharan Africa to determine the value of stability and AMMI analyses in Musa trials. The interpretation of the results, especially those concerning the genotype × environment interaction, was facilitated by the combination of stability and AMMI analyses. Tetraploid hybrids combining heavy and stable bunch mass were identified. The results also suggested that a clone should be assessed in the ratoon cycle because plantain and banana are perennial crops. Likewise, high yielding clones with specific adaptation should be selected in environments showing the respective environmental or biotic stress.

Physiological responses of banana (MusaAAA; Cavendish sub-group) in the subtropics. VII. Effects of windbreak shading on phenology, physiology and yield

SummaryThe influence of windbreak shading was investigated over the plant crop (P) and first ratoon (R1) cycle of bananas cv. Dwarf Cavendish, to quantify its effects on assimilation, phenology and yield in the subtropics. Plants growing under seasonal windbreak shading (late autumn to early spring) were compared with those growing under full sun but under similar windbreak protection. Windbreak shading reduced average photosynthetically active radiation (PAR) by 69%, which in turn reduced photosynthesis rate by 27%, transpiration rate by 38% and stomatal conductance by 40% compared with plants growing in full sun. Pseudostem temperature was 2.1 K lower on plants growing in shade. This led to a reduction in monthly leaf emergence rate and an extended cycle time. An additional extension to cycle time was caused by the extra 3.4 leaves produced before flowering on plants growing under windbreak shading. The decreased photosynthesis of leaves growing in shade was partially compensated for in the P cycle by a...

Root dynamics in plant and ratoon crops of sugar cane

The root system of a sugar cane crop on an Ultisol in northeastern Brazil was examined throughout the plant and first ratoon crop cycles, using both coring and minirhizotron methods. Total root masses (living plus dead, 0.9–1.1 kg m-2) and live root lengths (14.0–17.5 km m-2) were greater during the ratoon cycle than at the end of the plant cane cycle (0.75 kg m-2 and 13.8 km m-2, respectively). Root die-back during the two weeks following ratoon harvest was estimated to be 0.15 kg m-2, about 17% of the total root mass. Root die-back after the plant cane harvest was lower because fire was not used at this harvest and soil humidity was higher under the accumulated litter. A small amount of fine roots proliferated in the litter layer, amounting to 1% of the total mass and 3% of the total length. Root turnover could not be accurately assessed from minirhizotron observations due to variation in the relationship between coring data and the minirhizotron data with both time and soil depth.

The influence of functional leaf removal at flower emergence on components of yield and photosynthetic compensation in banana

The probability was tested that by removing ‘surplus’ banana leaves (cv. Williams) at flower emergence, sucker growth of the following cycle could be accelerated without affecting bunch development of the current cycle. Treatments applied at flower emergence stage of three successive cycles were no leaf pruning (control, 14-16 leaves); removal of half or three quarters of the total leaves, or cutting each leaf back by 50%. In a subsequent experiment using vigorous tissue culture plants, from one to 12 leaves were retained at flower emergence. Photosynthesis was measured in relation to pruning and leaf age. With four leaves retained, ratoon cycles were shorter but bunch mass was reduced to a greater extent, decreasing annual yield per ha by 12.6 and 19.4% in the R1 and R2 cycles respectively. Harvested fruits also softened more quickly when fewer than six leaves were present after flower emergence. Net C02 uptake increased by up to 35% on pruned plants. This compensation together with the greater photosynt...

Plant density studies with banana (cv. Williams) in a subtropical climate. II. Components of yield and seasonal distribution of yield

SummaryThe influence of plant density and plantation age on bunch mass, components of bunch mass, yield per annum and yield distribution of banana cv. Williams, was investigated over five successive cropping cycles. The study was conducted at Burgershall Research Station in the subtropical Eastern Transvaal, and density treatments were 1000, 1250, 1666 and 2222 plants ha−1. In the plant crop (PC) maximum bunch mass was 30 kg compared with 50 kg in each, of the four ratoons. In cycles R2 to R4, bunch mass was reduced significantly at the highest density due mainly to fewer hands per bunch and shorter and smaller fingers. Yield per annum was significantly higher (30%) at 2222 than at 1666 plants ha−1 for the PC and also cumulatively (6%) when averaged over all five cycles. However, in each of the four ratoon cycles, differences in yield per annum between these two densities were not significant, due to increased interplant competition at 2222 plants ha−1, which did not occur in the PC. At 1250 plants ha−1 h...