Canopy Root Research Articles

Growth of arabica coffee seeds (Coffea arabica L.) Sigarar Utang Variety as a response of treatment of various growth regulators and types of shade

Productivity of arabica coffee (Coffea arabica L.) Sigarar Utang Variety in Indonesia is still relatively low, especially in Simalungun Regency, Sumatera Utara. Some factors that need to be considered in nurseries are growth regulator and shade. This study aims to find out information on the type of growth regulators and the best shade density for the growth of arabica coffee seedlings. The experiment was carried out from March to June 2022 in Nagori Ujung Bawang, Simalungun Regency and Research Laboratory, Faculty of Agriculture, Universitas Sumatra Utara. The experiment used a Split Plot Design consisting of 2 factors and repeated 3 times. The first factor (main plot) consists of 4 levels, namely without shade, 50%, 70%, and 90% shade, while the second factor (sub-plot) consists of 3 levels are auxin growth regulator, cytokinin, and the combination of auxin with cytokinin. The results showed that the interaction of shade treatment and growth regulators had a significant effect on root canopy ratio. Root canopy ratio had a significant effect on the interaction of 90% shade treatment and a combination of auxin cytokinin of 5.27 g.

Kombinasi Pemupukan Organik dan Anorganik Terhadap Laju Pertumbuhan dan Rasio Bobot Basah Tajuk Akar Tanaman Padi Sawah (Oryza sativa L.)

Rice as one of the main food sources for the Indonesian people, especially North Sumatra, is still not able to meet the needs even though it has large land potential, so it is necessary to increase production through fertilization. This study aims to determine the effect of a combination of organic and inorganic fertilization on the growth of paddy rice plants. This study used a factorial randomized block design consisting of three factors, namely KCL (K) at 4 dose levels, namely K0 (0 kg/ha), K1 (25 kg/ha), K2 (50 kg/ha) and K3 (75 kg/ha). ), Urea (U) two levels namely U1(250 kg/ha) and U2 (225 kg/ha), Straw Compost (J) 2 levels namely J0 (0 tons/ha) and J1 (5 tons/ha) with a total The treatment combinations were 16 and consisted of 3 replications and 48 samples. Held in the rain-fed rice field area of Clove Turi sub-district, Binjai City. Soil sample analysis was carried out at the Analytical Laboratory of PT. Socfin Indonesia (SOCFINDO), Medan City and the Research and Technology Laboratory, Faculty of Agriculture, University of North Sumatra. The combination of inorganic and organic fertilizer treatments consisting of Potassium, Urea and Straw Compost showed no significant effect on the observed parameters of plant growth rate (cm/week) and root canopy wet weight ratio (grams). The highest plant growth rate was shown by the interaction of the three treatments, namely K3U2J0 of 10.33 cm/week, while the lowest data was shown by the interaction of the three treatments, namely K1U2J0 of 8.87 cm/week. The highest root canopy wet weight ratio was shown by the interaction of the three treatments, namely K1U1J0 of 8.69 grams while the lowest data was shown by the interaction of the two treatments between potassium and straw compost, namely K2J0 of 5.01 grams.Keywords: Fertilizer; Organic; Inorganic; Growth; Paddy

Photosynthetic electron transport rate and root dynamics of finger millet in response to Trichoderma harzianum

ABSTRACT Finger millet (ragi) is the main food grain for many people, especially in the arid and semiarid regions of developing countries in Asia and Africa. The grains contain an exceptionally higher amount of Ca (>300 mg/100 g) when compared to other major cereals. For sustainable production of ragi in the current scenario of climate change, this study aimed to evaluate the impact of Trichoderma harzianum (TRI) on ragi performance. The performance of photosynthetic pigment pool, photosynthetic apparatus, and root dynamics of three varieties of ragi (PRM-1, PRM-701, and PRM-801) in response to four treatments viz., C (soil), S+ TRI (soil + Trichoderma), farmyard manure (soil+ FYM), and FYM+TRI (Soil + FYM + Trichoderma) were studied. Results have shown a significant increase in the photosynthetic pigment pool and optimized functional and structural integrity of the photosynthetic apparatus in response to the combination of farmyard manure (FYM) with TRI. Higher yield parameters viz., φ(Po) and φ(Eo), δ(Ro), efficiency ψ(Eo), performance indices – PIabs and PItotal, and enhanced root canopy and biomass were observed in all three varieties. Improved electron transport from PSII to PSI, root canopy and biomass, may also suitably favor biological carbon sequestration to retain soil health and plant productivity in case grown in association with FYM and TRI.

PENGARUH PEMBENAH TANAH TERHADAP PERTUMBUHAN DAN PRODUKSI TIGA VARIETAS PADI PADA TANAH ASAL KARANGANYAR BERBASIS PUPUK ORGANIK BIO-SLURRY

The study aimed to compare the growth and production of rice between three varieties, namely Ciherang, IR 64 (Membrano), and Inpari 23 (Aromatic) without or with soil amendment application (dolomite) on andosol soil from Karanganyar. The research design used was a split-plot with a Completely Randomized Design. The main plot is treatment without soil amendment (R1) and with soil amendment (dolomite) (R2). Subplots were Ciherang (V1), IR 64 (V2), and Inpari 23 (V3) varieties. Parameters observed were plant height, number of panicles, panicle emergence age, crown weight, root weight, root crown ratio, strawweight, grain weight, 1000 grain weight, and harvest index. The results showed that the variety factor had a significant effect (P<0,05) on the age of panicle emergence and the number of panicles. The age of panicle emergence and the best number of panicles was found in the IR 64 variety. Variety factors had no significant effect on plant height, crown weight, root portion weight, root canopy ratio, strawweight, grain weight, 1000 grain weight, and harvest index. Soil amendment factors have no significant effect on growth, biomass production, and rice production. It can be concluded that the most superior rice growth and production is IR 64 variety followed by Ciherang and Inpari 23 varieties.

Application of silica nutrients to improves local rice productivity under saline conditions

Silica is beneficial nutrients that affect rice plants to be tolerance to biotic and abiotic stresses, include saline conditions. The aim of this research was to examine the effect of silica nutrients to the productivity of local rice accession PH 1 under saline conditions. The research used a factorial completely randomized design. The first factor is levels of salinity include non-saline, 4 dS m−1, 8 dS m−1, and 12 dS m−1. The second factor is the addition of silica nutrients per kg soil include 300 mg, 450 mg, and 600 mg. Salinity and the addition of silica nutrients were not significantly different to root canopy ratio, plant growth rate, and harvest index. However, the addition of silica nutrients up to 600 mg affects increasing of productivity up to 1.18 tonnes ha−1. There is an interaction between salinity and the addition of silica nutrients to the number of productive tillers, when the plant was given saline conditions 4 dS m−1 to 8 dS m−1, plant needs the addition of silica nutrients as much as 450 mg to 600 mg. While increasing the saline conditions up to 12 dS m−1 plant needs the addition of silica nutrients as much as 300 mg.

Correlation between carbohydrate content, protein, and fat with compatibility of durian seed grafting (durio zibethinus. Murr)

Durian nurseries can be done using generative and vegetative material sources. Both sources of propagation have their respective weaknesses and strengths. To get quality seeds requires a combination of two sources of propagation material that has each of the advantages that can complement each other. The process of merging can be through grafting. The grafting method in durian nurseries can use side grafting and shoot grafting methods. The purpose of this study was to determine differences in levels of protein, carbohydrates, fats, and phytohormones from various sources and storage time of the stem. This study was compiled based on factorial designs in the Randomized Group Design (RCBD). The first factor is the source of the stem (S), which consists of 3 sources, namely the primary branch (S1), secondary branch (S2), tertiary branch (S3). The second factor is the length of storage of the stem (T) which consists of 4 levels of storage time of the scion namely: 0 days (T0), 2 days (T1), 4 days (T2) and 6 days (T3). It was concluded that the carbohydrate content of the sciots gave the highest positive contribution to the increase in the number of shoots followed by the number of leaves, percentage of living grafts, leaf area, leaf area ratio, root canopy ratio, shoot length, and stem diameter. The protein content cannot contribute to the growth of grafted seeds even has a tendency to inhibit growth. The fat content in the scion does not contribute to the growth of plant variables.

Winter Pruning: Effect on Root Density, Root Distribution and Root/Canopy Ratio in Vitis vinifera cv. Pinot Gris

As in any other plant, the grapevine roots play a vital role in terms of anchorage, uptake of water and nutrients, as well as storage and production of chemicals. Their behaviour and development depend on various factors, namely rootstock genetics, soil physical and chemical features, and field agronomic practices. Canopy management, involving techniques such as defoliation and pruning, could greatly influence root growth. To date, most of the studies on grapevine winter pruning have focused on the effects on yield and quality of the grapes achievable through different pruning systems and techniques, while knowledge regarding root distribution, development, and growth in relation to winter pruning is still not completely understood. In this context, the purpose of our study was to investigate the effect of winter pruning on the root system of field-grown Vitis vinifera cv. Pinot Gris grafted onto rootstock SO4. We compared two pruning treatments (pruned-P and no pruned-NP) and analysed the effect on root distribution and density, the root index, and the root sugar reserve. Root data were analysed in relation to canopy growth and yield, to elucidate the effect of winter pruning on the root/yield ratio. Our data indicated that: (1) winter pruning stimulated the root growth and distribution; (2) canopy development was not negatively affected by this technique; (3) no pruned treatment produced less growth of the roots but a larger canopy. Information regarding both root growth and root canopy ratio is important as it gives us an understanding of the relationship between the aerial and subterranean parts of the plant, how they compete, and finally, offers us the possibility to ponder on the cultural practices.

Analysis of turbulent flow structures in the straight rectangular open channel with floating vegetated islands.

Floating vegetated islands (FVIs) are extensively implemented in various river ecology restoration projects, given their capability of decontaminating pollutants. The fluid dynamical behaviors of turbulence through FVIs are studied in the flume by using the SonTek Acoustic Doppler Velocimetry. Through conventional spectral and quadrant analyses, flow characteristics, such as energy content and turbulent momentum exchange, are investigated as the flow encountered a series of root canopies. A shear layer with corresponding coherent vortex structures at the bottom of root canopies occurred, which is generated by Kelvin-Helmholtz instabilities. These instabilities are usually derived from velocity differences between root canopy and gap region. Shear- and stem-scale vortices are identified by using spectral analysis. The power spectral density function on measured vertical velocity fluctuations in the flow direction near the bottom of root canopies from the leading edge of FVIs is computed. Given the flow developing downstream, a series of the spectral curves has gradually showed one dominant dimensionless frequency at 0.046. The sweep and ejection events have contributed prominently to the Reynolds stress in whole vertical direction. Momentum flux carried by sweeps outweighs its counterpart carried by ejections inside root canopies. However, the situation is different outside root canopies. The sweep-ejection contributions are brief but crucial to the total turbulent momentum exchange, which is in good agreement with considerable studies on turbulent flow through canopies.

Korelasi Antara Kandungan Karbohidrat, Protein, dan Lemak dengan Kompatibilitas Grafting Bibit Durian (Durio zibethinus Murr.)

Pembibitan Durian dapat dilakukan dengan menggunakan sumber bahan generatif dan vegetatif. Kedua sumber propagasi ini memiliki kelemahan dan kekuatan masing-masing. Bibit berkualitas diperoleh melalui kombinasi dari dua sumber bahan perbanyakan yang memiliki masing-masing kelebihan yang dapat saling melengkapi. Proses penggabungannya bisa melalui mini grafting. Metode mini grafting di pembibitan durian dapat menggunakan cara grafting samping dan grafting pucuk. Penelitian ini ingin mengkaji hubungan kandungan karbohidrat, protein, dan lemak terhadap keberhasilan pertumbuhan hasil mini grafting pada tanaman durian. Penelitian dilaksanakan dengan menganalisis kandungan karbohidrat, protein dan lemak pada batang atas yang akan digunakan untuk grafting, serta mengamati dan mengukur proses pertumbuhan tanaman hasil mini grafting. Kandungan karbohidrat pada batang atas memberikan kontribusi positif tertinggi terhadap peningkatan jumlah tunas diikuti oleh jumlah daun, luas daun, perbandingan luas daun, perbandingan pupus akar, panjang tunas, dan diameter batang. Kandungan protein dan kandungan lemak tidak dapat berkontribusi pada pertumbuhan bibit okulasi bahkan memiliki kecenderungan untuk menghambat pertumbuhan.

SERAPAN SI DAN P SERTA PERTUMBUHAN PADI GOGO (Oryza sativa L.) YANG DIAPLIKASIKAN ABU SEKAM PADI DAN PADA MEDIUM ULTISOL

ABSTRACT The main problems of rice cultivation in Ultisol medium are acid reactions, Al saturation and height P fixation, as well as low availability macro, micro nutrients especially Mo and Si. Rice plants need silicate in large quantities even though it is not an essential nutrient, therefore husk ash can be used as a source of Si. P availability increased by applying P fertilizer which was classified as slow realease so that fixation can be supported. The research aims to study the interaction of rice husk and rock phosphate is able to improve Si and P uptake and the growth of upland rice growth on Ultisol medium. The research was conducted at the Green House of the Faculty of Agriculture, University of Riau, Pekanbaru from January to March 2019. The research in form factorial experiment 4×3 was arranged in a completely randomized design, 3 replications. The first factor was rice husk consist of 4 levels (0, 1,5, 3, and 4,5 ton ha -1 ). The second factor was rock phosphate consist of 3 levels (0, 25, 40 kg P 2 O 5 ha -1 . The results showed the application of rice husk dose of 3 ton.ha -1 and rock phosphate dose of 25 kg P 2 O 5 ha -1 increased Si and P uptake, P uptake efficiency, the root volume, dry weight, root canopy ratio, and plant growth rate.

Patterns and dynamics of canopy-root coupling in tropical tree saplings vary with light intensity but not with root depth.

Carbon (C)dynamics in canopy and roots influence whole-tree carbon fluxes, but little is known about canopy regulation of tree-root activity. Here, the patterns and dynamics of canopy-root C coupling are assessed in tropical trees. Large aeroponicsfacility wasused to study the root systems of Ceiba pentandra and Khaya anthotheca saplings directly at different light intensities. In Ceiba, root respiration (Rr ) co-varied with photosynthesis (An ) in large saplings (3-to-7-m canopy-root axis) at high-light, but showed no consistent pattern at low-light. At medium-light and in small saplings (c. 1-m axis), Rr tended to decrease transiently towards midday. Proximal roots had higher Rr and nonstructural carbohydrate concentrations than distal roots, but canopy-root coupling was unaffected by root location. In medium-sized Khaya, no Rr pattern was observed, and in both species, Rr was unrelated to temperature. The early-afternoon increase in Rr suggests that canopy-root coupling is based on mass flow of newly fixed C in the phloem, whereas the early-morning rise in Rr with An indicates an additional coupling signal that travels faster than the phloem sap. In large saplings and potentially also in higher trees, light and possibly additional environmental factors control the diurnal patterns of canopy-root coupling, irrespective of root location.

PENGARUH KONSENTRASI IAA DAN BERBAGAI JENIS MEDIA TUMBUH TERHADAP PERTUMBUHAN TANAMAN SELEDRI (Apium graveolens L.) DENGAN SISTEM BUDIDAYA HIDROPONIK FERTIGASI

The purpose of the study was to determine the effect of IAA concentration and various types of media growing on celery plant growth with a fertilizing hydroponic cultivation system in interaction as well as each of the main influences. The design used in this study is the Design of Divided Plots in the form of Complete Randomized Design consisting of two factors. The first factor is IAA (A) with a concentration of 0, 1, 10, 100 ppm while the second factor is Various Types of Growing Media (M), namely Cocopeat, Husk Charcoal, Sawdust Powder, Hydroton. The parameters observed were plant height (cm), economical wet weight (g), root volume (cm3), average net assimilation rate (g /cm2/day), average relative growth rate (g /day), number of tillers (fruit), root canopy ratio (g). The last observation data were analyzed statistically and continued with a BNJ follow-up test at the level of 5%. The results showed that the interaction of IAA concentrations and various types of media grew significantly on the parameters of the plant's wet weight, root volume, and root canopy ratio. The best treatment was found in a combination of treatment of 1.0 ppm IAA concentration and cocopeat growing media. The main effect of IAA concentration was real on all observed parameters. The best treatment is 1.0 ppm IAA concentration. The main influence of various types of media grows significantly for all observational parameters. The best treatment is the cocopeat media.

The effect of soil volume on the growth of roots and canopy of Opuntia ficus-indica

The influence of soil volume on root development and canopy growth rates of cactus pear (Opuntia ficus-indica) was studied at Palermo University, Italy, in 2014-2016. In November 2014, 60 1-year-old O. ficus-indica cladodes were planted in pots containing five different soil volumes, 50, 33, 18, 9 or 5 L, in a complete randomized design with three replications. Root dry mass, total number of cladodes and canopy dry mass were measured after 6, 12, 18 and 24 months. The results revealed a significant effect of soil volume and sampling time and their interaction (P<0.01) on root dry mass, total number of cladodes and canopy dry mass. Root dry mass ranged between 23 and 206 g, with the highest value for plants grown in 50 L soil volume, sampled after 24 months of planting. The highest number of cladodes was produced by the plants raised in the highest soil volume (50 L) after 24 months of planting and the lowest number was in the lowest soil volume (5 L). A linear increase in canopy dry mass was observed with respect to increased soil volume. Increased soil volume had a significant and positive effect on the roots:canopy dry mass ratio. It is concluded that the restriction of soil availability in O. ficus-indica resulted in major growth limitation for root and canopy.

PEMANFAATAN KOMPOS TANDAN KOSONG KELAPA SAWIT DENGAN BAKTERI SELULOLITIK DAN LIGOLITIK SERTA NPK TERHADAP PERTUMBUHAN BIBIT KAKAO (Theobroma cacao L.)

ABSTRACT Cocoa ( Theobroma cacao L.) is one of the large plantations after oil palm. The increase in cocoa nursery can be accompanied by the utilization of waste derived from palm oil, namely oil palm empty fruit bunches (OPEFB). oil palm empty fruit bunches can be useful as organic fertilizer because it can improve soil physical, chemical and biological properties. The use of OPEFB as organic fertilizer will also reduce excessive use of NPK. Utilization of OPEFB into organic fertilizer can be in the form of compost or raw OPEFB organic matter plus cellulolytic and lignolytic microbes. This study aims to determine the effect of NPK fertilizer and OPEFB compost on the growth of cocoa seedlings. This research was conducted experimentally using a completely randomized design consisting of nine treatments and three replications. Parameters of observation were plant height, stem diameter, number of leaves, root canopy ratio, dry weight of seedlings and age of planting. The results showed that the provision of 100 g polybag -1 OPEFB compost plus 50% NPK fertilizer (2 g polybag -1 ) could provide good growth in cocoa seeds ( Theobroma cacao L.).

The application of different Bacillus subtilis contained formula as bio fungicide tablet to control Ganoderma boninense in oil palm nurseries

This study aimed to determine effect of different Bacillus sp. endophytic contained formula as bio fungicide tablet to control Ganoderma boninense in oil palm nursery. A Complete Randomized Design, 5 treatments and 4 replicates were used. The treatments were different formula namely: F0 = Bacillus sp. endophytic, F1 = Bacillus sp. endophytic + sago starch + peat + tapioca flour, F2 = Bacillus sp. endophytic + corncobs flour + sago dregs + tapioca flour, F3 = Bacillus sp. endophytic + solid + talk + tapioca flour, F4 = Bacillus sp. endophytic + pineapple skin flour + zeolite + tapioca flour. Data were analyzed using ANOVA at a = 5%. The results showed that all formulas were able to slow down incubation period and reduce disease intensity. However, the increase of seedlings height, number of leaves, increase in tuber diameter, root volume, root canopy ratio and dry weight of roots is not affected. F3 was found as best formula due to able control G. boninense by slowing down disease incubation period and reduce its intensity to 0% within 140 days. That formula also shows better in increasing seedling height, number of leaves, diameter of stem, root volume, and weight dried root.

Respon Pertumbuhan Akar Beberapa Hasil Persilangan Populasi F1 Tanaman Jagung (Zea mays L.) terhadap Cekaman Besi (Fe) pada Media Kultur Hara

The aims of the research were to know The Root Growth Response of Some crosses F1 Corn Populations (Zea mays L.) at Iron Stress (Fe) in Medium of Nutrient Culture. This research was conducted at the greenhouse Faculty of the Agriculture University of Sumatera Utara, Medan from March to April 2017. The research used Randomized Block Design (RBD) with two using two factors i.e : F1 population (NEI 9008 x CLA 46, CLA 84 x NEI 9008, CLA 106 x NEI 9008, CLA 16 x CLA 84, and CLA 84 x P1027) and iron stress treatment (0, 50 ppm, and 100 ppm). The results showed that the F1 population had a significant effect on root-canopy weight, root volume, and root canopy ratio. Iron stress treatment with different concentrations had a significant effect on root distribution parameters, root canopy ratio, root length, and the extension of root length. The interaction between F1 population and iron stress has a significant effect on root volume character. Iron treatment with a concentration of 100 ppm can still be tolerated by the F1 population of maize crops on nutrient culture. The CLA 16 x CLA 84 populations had a better adaptation to the iron stress treatment in nutrient culture media. The CLA 16 x CLA 84 had lower stress sensitivity index value and a smaller productivity gap on root dry weight.

Produksi selada (Lactuca sativa l.) dengan penyinaran lampu led merah dan biru di malam hari pada teknologi hidroponik sistem terapung termodifikasi

This research has an aim to observe the production of lettuce (Lactuca sativa L.) on hydroponic technology of floating system with red and blue LED (Light Emitting Diode) at night. This research was conducted inside the Screenhouse in which located on the top of Griya Kads House building, Bulusan Village, Tembalang Sub-district from May to June 2017. The research was conducted by 3x3 factorial experiments in Nested Design with 3 replications. The first factor was 0, 1.5 and 3 hours irradiation of red and blue LED lights at night. The second factor was 3, 5 and 7 ml/liter of AB mix nutrient concentration which was nested in the first factor. The data collected were fresh weight, dry weight and root canopy ratio. The results of the study showed that the treatment of AB mix nutrient concentration had no significant effect on all parameters. The production of lettuce with level of 5 ml concentration of AB mix was quite good, yet 3 ml and 7 ml levels didn’t improve lettuce production. The duration of red and blue LED irradiation only resulted in an increase in the production of canopy fresh weight. This research can be concluded that 3 hours was sufficient to give the good results to improve the results of lettuce plants production. Keywords : Lettuce Production, AB Mix Nutrition, Red and Blue LED.

Growth and yield of patchouli (Pogostemon cablin, Benth) due to mulching and method of fertilizer on rain-fed land

The drought stress that occurs during growth results in a drastic reduction in growth and yield. This study was aimed to study the effect of mulching and method of fertilizer application in reducing the impact of drought stress on patchouli plants. The experiment was conducted from July to December 2016 using a split plot design into three replications with two treatment factors. The first factor was mulch factor with three levels, i.e. M0 (without mulch), M1 (rice straw mulch) and M2 (silver black plastic mulch). The second factor was the method of fertilizer application consisting of three stages: C1 (once), C2 (twice), C3 (three times). The parameters included plant height, number of branches, number of leaves, root length, wet weight of plant, root canopy ratio, total of chlorophyll, soil temperature and soil moisture content. The results showed the use of straw mulch reduce the impact of drought stress on patchouli plants. Two times fertilizer application gave better growth and yield. The use of straw mulch produced lower temperature degrees and maintained soil moisture content.

Effect of Cocoa Pod Husk Compost Produced Using Rot Fungi on the Growth of Cocoa Seedlings

Rot fungi have the ability to decompose organic materials into simple compounds or elements as nutrients for plants. In the process, rot fungi produce secondary metabolites and absorb phosphate from their substrates so that the phosphate become available to plants. The purpose of this study was to identify the species of rot fungi isolated from decaying cocoa stems and to determine the ability of the rot fungi insolubilizing phosphate and the effect of the husk compost on the growth of cocoa seedlings. The rot fungi were isolated and purified before they were grown on solid Pikovskaya’s media amended with 0.5% tricalcium phosphate (Ca3PO4) as a phosphate source. In addition, the effects of compost addition to growth medium (soil: compost = 2:1) on cocoa seedling growth was also determined. The results showed that there were eight species of rot fungi isolated from dead cocoa trees: Mycena sp., Lycoperdon sp., Auricularia sp., Schizoshyllum sp., Coprinus sp., Tremetes sp., Pleurotus sp. and Tremella sp. All isolates were capable of solubilizing phosphate from substrates but amongst all isolates, Lycoperdon sp. and Pleurotus sp. were the most effective in solubilizing phosphate, 3,198 and 3,094 μg L-1, respectively. Effect of the compost produced using these two rot fungi on plant growth variables: the ratio of leaf area, plant dry weight, root canopy ratio and net assimilation rate, were comparable to chemical fertilizers. Thus, Lycoperdon sp. and Pleurotus sp. are promising decomposing agents for producing high quality compost made from cocoa pod husks as an alternative to inorganic fertilizers.

Effects of soil drenching of water-soluble potassium silicate on commercial avocado (Persea americana Mill.) orchard trees infected with Phytophthora cinnamomi Rands on root density, canopy health, induction and concentration of phenolic compounds

Avocado root rot, caused by Phytophthora cinnamomi Rands, remains a major constraint to avocado production worldwide. In the current study effects of successive soil drench applications of soluble potassium silicate on canopy health and root density of 13-year-old Persea americana Mill. trees infected with P. cinnamomi were investigated. Soil drenching with 20 l per tree of a 20 ml l-1 soluble potassium silicate solution (20.7% silicon dioxide) resulted in significantly higher root density when compared to untreated control trees, and trees injected with potassium phosphonate (Avoguard®) during most but not all evaluation dates. Three successive drenches of soluble potassium silicate resulted in the most significant increase in root density. A similar effect was seen on canopy health. In general, total soluble phenolic concentrations were significantly higher between March 2005 and January 2006 in those trees drenched three times with soluble potassium silicate per growing season (up to 72.62 µg l-1) compared to trees injected twice with potassium phosphonate per growing season (up to 68.77 µg l-1) and untreated control trees (51.62 µg l-1). This evidence suggests that multiple or even continuous applications of soluble potassium silicate to avocado trees will be required to effectively suppress Phytophthora cinnamomi over the entire growing season.