Increased Tuber Yield Research Articles

Bacterial communities are associated with the tuber size of Tetrastigma hemsleyanum in stony soils

Plants grown in stony soils have better developed root systems and higher crop yields. The roles of physical and chemical effects of stony soils on plant growth have been published, but the roles of soil microbiota have not been investigated. In this study, Tetrastigma hemsleyanum plants were cultivated for 2 years in stony soils and the same soils after removing rock fragments (non-stony soils). The composition of bacterial community and the tuber transcriptome were analyzed, using multiple bioinformatics methods. Compared with non-stony soils, stony soils supported a significantly different bacterial community, which was associated with larger tuber size of T. hemsleyanum. Stony soils had greater bacterial diversity, co-occurrence network complexity, and greater abundance of bacterial taxa belonging to Actinobacteria, Rokubacteria, Rhizobiales, Desulfarculaceae, and Chthoniobacteraceae than the corresponding microbiota in non-stony soils. The differential soil bacterial communities between stony and non-stony soils may be mainly driven by soil physicochemical properties, such as available S, organic matter, and pH. The discriminatory bacterial taxa of soils shaped the bacterial communities of rhizosphere soil, and tuber surface soil (TS), which was strongly correlated with tuber size parameters. In addition, the potential functions of the discriminatory bacterial taxa in TS corresponded closely with gene pathways of the host, like phytohormone biosynthesis, photosynthesis, and biotic stress resistance, which are crucial for the initiation and development of tubers. These results not only help us to better understand the role of stony soils in improving plant growth but also provide a reference for increasing tuber yield through the use of microbial inocula.

Determination of Suitable Deficit Irrigation Stage in Potato Production

Water deficiency is the major limiting factor for potato yield promotion. Increasing tuber yield and decreasing consumption of water at the same time are a challenge in development of new potato cultivar. Deficit irrigation is regarded as one of the promising approaches to solve this problem, however no practical technique has been proposed in potato production as yet. By setting different deficient irrigation regimes and investigating potato growth and water use efficiency, we found that only application of deficit irrigation at the seedling stage could achieve the goal of increasing water use efficiency and maintaining marketable tuber yield at the same time. Almost half of the normal full irrigation doubled promotion effects on water efficiency and yield, especially the marketable tuber yield. This may be mainly attributed to establishment of a strong root system, including longer root length and larger root surface area under water deficit at the seedling stage. Based on such a root system at the early development stage, leaf area index and dry matter accumulation were optimized at the later developmental stages. Thus, maintaining water deficit at the seedling stage with enough water supplied at the tuber initiation and bulking stages should be practiced in potato production in water limited areas.

Vertical rotary sub‐soiling affects soil moisture characteristics and potato water utilization

AbstractVertical rotary sub‐soiling (VRT) has potential to increase potato (Solanum tuberosum L.) yields in semiarid rainfed area. However, despite the importance of this food crop, little research had been done on this topic. We describe results from a field experiment carried out during 2016–2017 in a semiarid area (104°36′E, 35°35′N), where potato crop was grown in a field with three tillage treatments: (a) vertical rotary sub‐soiling to a depth of 40 cm (VRT), (b) sub‐soiling to a depth of 40 cm (SS), and (c) traditional rotary tillage to a depth of 15 cm (TT as control). The results showed that the VRT decreased soil bulk density by 0.8–22.2 and 13.3–25.3% compared with SS and TT, respectively, leading to increased porosity (by 12.5–14.8 and 12.3–23.7%) and saturation water content (by 23.7–33.2 and 25.6–59.0%), together with reduced water content at wilting point (by 12.5–23.4 and 11.4–23.4%). This was equivalent to 23.7–33.2 and 25.2–59.0% increase in soil maximum available water (SMAW) of the soil profile down to 40‐cm depth compared with SS and TT, respectively. The increased SMAW resulted in increased tuber yield by 156.8 and 47.8%, corresponding increases in water use efficiency by 92.3 and 19.2% in 2016 compared with SS and TT, respectively. The similar results were observed in 2017. Our results demonstrate that VRT was an effective technology to further increase water use efficiency and crop yield on top of plastic film mulching in semiarid rainfed area.

Map-based site-specific seeding of seed potato production by fusion of proximal and remote sensing data

Uniform rate seeding (URS), adopted by the majority of farmers worldwide, is an inappropriate approach particularly in fields with large variability to optimize seeding rate that is crucial to manage farm resources sustainably. The objective of this study was to examine the potential of map-based site-specific seeding (SSS) of seed potato for improving crop yield and economic return. A 6-ha-field was scanned using an on-line visible and near infrared (vis-NIR) spectroscopy and an electromagnetic induction (EMI) sensor. Two SSS treatments were adopted based-on two types of management zone (MZ) maps, delineated with K-means clustering algorithm, and these were compared with the URS. The first treatment was based on a MZ map developed using EMI data (EMI-SSS), whereas the second treatment was based on fusion of vis-NIR measured soil data with Sentinel-2 derived normalized difference vegetation index (visNIRsen-SSS). Seed potatoes (Solanum tuberosum L. cv. Hermes) were planted at 11, 13, 15, 17 and 19 cm seed-to-seed spaces according to “Kings” principle i.e., sowing more seeds to the most fertile zones and vice-versa. Results showed that both SSS approaches have resulted in increased tuber yields (EMI-SSS: 32.42 t/ha, visNIRsen-SSS: 31.89 t/ha) and higher economic return, compared to URS . Although visNIRSen-SSS provided lower gross yield than EMI-SSS, the larger yield of small size (28−45 mm) tubers, having higher market price than other size categories has resulted in actual market price for the former being higher than that of the latter approach. The visNIRsen-SSS and EMI-SSS produced net returns of 4995 €/ha and 4947 €/ha, respectively, which were more than that of the URS of 4528 €/ha, by 467 €/ha and 419 €/ha, respectively. In addition, visNIRsen-SSS approach has saved seeding costs by 14 €/ha though EMI-SSS consumed 5 €/ha more compared to URS. Therefore, it is recommended to adopt SSS (particularly visNIRsen-SSS) for seed potato production, as a means of increasing crop yield, reducing input cost and thus maximizing profitability compared to URS.

Effect of soil mulching on growth, productivity, and water use efficiency of potato (Solanum tuberosum L.) under deficit irrigation

Two field studies were conducted consecutively in the summer season of 2015 and 2016 to investigate the effect of different soil mulching materials (bare soil: BS as a control, white plastic: WP, black plastic: BP and rice straw: RS) on growth, productivity, and water-use efficiency (WUE) of potato under three levels of irrigation (I100=100%, I80=80%, and I60=70% of crop evapotranspiration). Growth characteristics, yield and its components, and WUE were significantly (P ≤ 0.05) affected by both irrigation level and mulching materials. All mulching materials effectively enhanced growth and productivity when compared to bare soil. Potato plants grown under BP and WP as well as RS showed higher mean values of large size (> 60 mm) tubers and WUE compared to non-mulched treatment (BS) in both seasons. Mulching treatments noticeably increased tuber yield in the order of BP > RS > WP. Results displayed that, under different soil mulching materials, the I80 strategy studied here could be successfully applied during summer season in commercial potato production allowing water savings of 20% without any detrimental effect on plant growth or productivity.

Assessment of the Nutritional and Medicinal Potential of Tubers from Hairy Stork's-Bill (Erodium crassifolium L 'Hér), a Wild Plant Species Inhabiting Arid Southeast Mediterranean Regions.

Emerging needs for diversifying human diet and to explore novel therapeutic procedures have led to increasing attempts to retrieve traditional nourishments and recruit beneficial wild plant species. Species of the genus Erodium (Geraniaceae) harbor medicinal indications and substances known from folklore and scientific research. Hairy stork’s bill (Erodium crassifolium L’Hér), is a small hemicryptophyte that inhabits arid southeast Mediterranean regions. E. crassifolium is among the very few Geraniaceae species known to produce tubers. Traditional knowledge holds that the tubers are edible and used by Bedouin tribes. However, no scientific information was found regarding nutrition or medicinal properties of these tubers. The objectives of our project are to unravel potential nutritional and medicinal benefits of the tubers, conduct initial steps towards domestication and develop agricultural practices enhancing E. crassifolium tuber yield and quality. Tubers show high water content (90%), low caloric value (23 Kcal 100−1 g) and considerable contents of minerals and vitamins. In addition, the tubers contain significant amounts of catechins and epigallocatechin, polyphenolic compounds known for their antioxidative, anti-inflammatory and antiproliferative activities. Furthermore, in vitro experiments demonstrated significant anti-inflammatory effects on human cell cultures. E. crassifolium is highly responsive to environmental changes; fertigation (700 mm) increased tuber yield by 10-fold, compared to simulated wild conditions (50–200 mm). These results indicate a significant potential of E. crassifolium becoming a valuable crop species. Therefore, there is a need for continued efforts in domestication, including ecotype selection, breeding, development of suitable agricultural practices and further exploration of its medicinal benefits.

Available Soil Nutrients and NPK Application Impacts on Yield, Quality, and Nutrient Composition of Potatoes Growing during the Main Season in Japan

Proper management of N, P, and K fertilizers is considered very important to maximize tuber yield and attain desirable processing quality. Generally, farmers apply NPK fertilizer rates based on the preplant soil tests. However, very limited information is available on the influence of available soil nutrients and in-season NPK application rates on yield and quality of tubers. In the present study, paired soil and tuber samples were evaluated from 170 commercial production sites to evaluate potential relationship between soil nutrients, tuber yield, and tuber quality. These paired samples gave us the opportunity to not only study yield response to fertilizer application rates but also study the relationship between soil nutrient availability and tuber nutrient concentrations. We found that about 50%, 80%, and 70% of farmers applied more NPK than recommended rates, respectively. Our results suggest that, in general available soil NPK increases tuber NPK concentrations and tuber N and K concentrations can reduce specific gravity. Interestingly, tuber P concentration had no effect on specific gravity. We also found some variations in these responses to nutrients (NPK) among cultivars suggesting some genetic control for the traits studied. Results also suggest that application of NPK fertilizers in excess of recommended rates on soils that are already rich in these nutrients does not increase tuber yields and may in fact increase potential environmental degradation associated with excessive fertilization and the cost of production.

ВЛИЯНИЕ ЗЕРНОБОБОВЫХ КУЛЬТУР КАК ПРЕДШЕСТВЕННИКОВ НА УРОЖАЙНОСТЬ И КАЧЕСТВО КАРТОФЕЛЯ

The purpose of the study is to study the possibility of using leguminous crops for grain as potato precursors. Field experiments were carried out in 2017–2019 in Krasnoarmeyskiy district of the Chuvash Republic. The soil of the experimental plot is gray forest, heavy loam granulometric composition with a humus content in the arable layer of 3.9%, mobile phosphorus - 140 and exchange potassium - 160 mg/kg of soil, pH - 5.1 units. Narrow leaf lupine, soybeans and fodder beans for grain were used as potato precursors; control was employed steam (vetch barley mixture for green fodder). Potato planting was carried out on May 10. The repetition of the experiment is 3 times, the size of the plots is 1.5 per 10 m, an area of 15 m2. The planting scheme of potatoes is 70 by 30 cm with embedment of tubers to a depth of 6 ... 8 cm. In the experiment, an early ripe variety Udacha was grown. Before planting, the tubers were treated with the insecto-fungicide Emesto Quantum (0.32 l/t). Plant care included pre-emergence and two post-emergence row-spacings cultivation, hilling, and weeding. The best precursors for potatoes are narrow-leaved lupins and soybeans. In these cases, there is a significant increase in tuber yield by 31.2 and 30.8%, dry matter - by 6.7 and 9.2%, and starch - by 4.3 and 5.5%, respectively.

Effects of Crop Rotation and Biocontrol Amendments on Rhizoctonia Disease of Potato and Soil Microbial Communities

Rotation crops and biocontrol amendments were investigated for suppression of Rhizoctonia solani on potato (Solanum tuberosum) and their interactive effects on soil microbial communities. Greenhouse trials were conducted to evaluate selected rotation crops, including barley, common and “Lemtal” ryegrass, clover, potato, and combinations of barley with ryegrass or clover, for their effects on populations of R. solani and Rhizoctonia disease. Potato and clover preceding potato resulted in higher disease severity than most other rotations, whereas ryegrass reduced stem canker severity. In addition, all ryegrass treatments resulted in substantially higher populations of R. zeae. Field trials evaluating selected biocontrol treatments in combination with different rotations were conducted at two locations in Maine. Potatoes were treated with the biocontrol organisms Laetisaria arvalis, Trichoderma virens, or Bacillus subtilis and planted following rotation crops of barley and ryegrass, barley and clover, or potato. The barley/ryegrass rotation significantly reduced incidence and severity of stem canker and increased tuber yield at one location. Efficacy of the biocontrol treatments varied by rotation and location, with L. arvalis and T. virens reducing black scurf in some rotations and increasing some aspects of tuber yield at one location. Soil microbial community characteristics differed among rotation crops and biocontrol treatments. Significant crop by biocontrol interactions were observed demonstrating the complex interactions among rotation crops, biocontrol treatments, and soil microbial communities, as well as indicating that biocontrol can be enhanced within beneficial rotations.

EFFECT OF FOLIAR SPRAY WITH DIFFERENT POTASSIUM SOURCES AND ZINC RATES ON GROWTH AND YIELD OF SWEET POTATO (Ipomoea batatas L.).

Two field experiments were carried out during 2017 and 2018 seasons atExperimental Farm, Faculty of Technology and Development (Ghazala Region –Zagazig City), Sharkia Governorate (Egypt) to investigate the effect of different potassium sources and zinc fertilizer levels on growth and yield of sweet potato plant cv. Menoufia 6. The experimentwas set up arandomized complete blocks design which included 7 treatments of different sources of potassium and zinc (EDDTA)rates(i.e., potassium silicate 2 mll-1 and 4 mll-1, potassium humate, 2 mll-1 and 4 mll-1 and zinc (EDDTA), 2 mll-1 and 4 mll-1, besides the control treatment without any addition . The obtained results could be summarized as follows: application of foliar spray with zinc (EDDTA) with4 mll-1, being the most effective treatment on vegetative growth and chemical composition, while 4mll-1 potassium silicate as foliar application caused a significantly increased in tuber yield and quality of sweet potato, followed by the treatment of 4 mll-1 zinc in most cases, in both growing seasons. Conclusively, it could be concluded that, using the treatment of 4 mll-1 zinc (EDDTA) caused an increases in plant growth parameters and chemical composition of sweet potato plant cv. Menoufia 6, while 4 mll-1 potassium silicate significantly increased tuber yield and quality.

The influence of flower removal on tuber yield and biomass characteristics of Helianthus tuberosus L. in a semi-arid area

Jerusalem artichoke (Helianthus tuberosus L.) is an important source of biomass for biofuels production. To evaluate its potential as a feedstock for biofuel, calorific value, ash, and carbon (C) and nitrogen (N) contents were investigated under different flower removal treatments during 2015–2016 in the Inner Mongolia autonomous region of China. Total biomass of flower removal treatments was significantly (P < 0.05) higher than that of the control, and the highest value was obtained when 50 % of the flowers were removed (735 g plant−1). Tuber biomass increasing gradually as the proportion of flowers removed increased. The highest value of tuber biomass was obtained when 100 % flowers were removed (228 g plant−1). Tuber yield of the 33 % and 50 % flower removal treatments was significantly higher than that of the 25 % flower removal treatment and control. The caloric value and N and C contents of tuber was improved while ash content of tuber was decreased with flower removal, compared to no flower removed. Total energy was the highest with removal of 50 % of the flowers 19,041 J plant−1). In contrast, the highest value of aboveground energy yield occurred with removal of 25 % of the flowers (7076 J plant−1), while underground energy yield was greatest with removal of 100 % of the flowers (4058 J plant−1). Removing 100 % flowers is an effective method to increase tuber yield and quality of Jerusalem artichoke in a semi-arid environment.

Evaluation of fungicides to control potato late blight (Phytophthora infestans) in the plains of Nepal

AbstractFungicide application is an effective management option to control late blight of potato (caused by Phytophthora infestans). Field experiments were conducted to evaluate the efficacy of recently introduced and previously used fungicides on late blight management and potato yields in the western plains of Nepal in 2015 and 2016 crop seasons. Fungicides and a non‐treated control (NTC) were replicated three times in a randomized block design planted with late blight susceptible cultivar Cardinal. Chlorothalonil, copper oxychloride, dimethomorph, fenamidone + mancozeb, mancozeb and metalaxyl were sprayed in 2015. In 2016, carbendazim was used instead of chlorothalonil. The area under disease progress curve (AUDPC) was consistently reduced in years by dimethomorph (90% and 65% in 2015 and 2016, respectively), fenamidone + mancozeb (68% and 62%) and mancozeb (40% and 47%) compared with the NTC. Similarly, tuber yield was increased with the application of dimethomorph (266% and 146% in 2015 and 2016, respectively), fenamidone + mancozeb (211% and 155%) and mancozeb (136% and 116%) compared with the NTC. Chlorothalonil reduced AUDPC by 43% and increased tuber yield by 170% in 2015. Other fungicides either had inconsistent results or did not reduce late blight severity and consequent effects on potato yield. The overall benefit–cost ratio was highest for dimethomorph in both years. These results show efficacy of dimethomorph, fenamidone + mancozeb and mancozeb in reducing late blight severity and increasing potato tuber yield in the plains of Nepal.

Evaluation of fungicides for management of late blight (Phytophthora infestans) of potato

Late blight disease of potato, causal agent, Phytophthora infestans (Mont.) de Bary, is one of the serious diseases for potato production. Application of fungicides is an effective management option to control late blight. Field experiment was conducted during winter season of 2018 for evaluation of the efficacy of fungicides on late blight management and potato yields in research field of Prithu Technical College, Institute of Agriculture and Animal Science, Gadawa, Lamahi Dang, Nepal. Six fungicides i.e. Relaxyl (Metalaxyl 8% + Mancozeb 64 %), Antracol (Propineb 70 %), Sectin (Mancozeb 50% + Fenamidone 10%), Dithan M 45 (Mancozeb 75 %), Targon (Metalaxyl 35%), Bavistin (Carbendazim 50 %) and a nontreated control (NTC) were replicated three times in a randomized complete block design planted with late blight susceptible potato variety Cardinal. Fungicide application considerably reduced late blight progress, with a corresponding increase in tuber yield. The least disease severity (18.67%), least disease incidence (5.33%), least mean AUDPC (85.56) and highest tuber yield (9.49 kg/plot) were recorded on application of Sectin @ 2 g/L. The disease incidence and AUDPC value was negatively corelated with the tuber yield. The result revealed that the fungicide Sectin was most effective in controlling late blight disease of potato and to increase tuber yield.

Potassium Fertilization for Fresh Market Potato Production in Tropical Soils

Potassium (K) is the most taken up and removed nutrient by potato (Solanum tuberosum L.), and has a great influence on tuber yield and quality. This study was performed to evaluate the effects of three rates (100, 200, and 400 kg K2O ha−1) and two timings of application of K (single application at planting furrow and split application of 50% at planting furrow plus 50% at hilling), as potassium chloride, as well as a control (without K application) on the plant nutrition and tuber yield and quality of potato ‘Agata’ grown in tropical clay soils. The split application of K fertilizer had little influence on plant nutrition and tuber yield and quality. The influence of K fertilization on increasing K and reducing Ca and Mg concentrations in the leaf was more significant in soil with low exchangeable K. In this soil, the maximum tuber yield (33.6 Mg ha−1; 107% higher than the control) was obtained with an estimated rate of 325 kg K2O ha−1, while in the soils with medium and high exchangeable K, the tuber yield was increased between 22 and 34% and only up to a rate of 200 kg K2O ha−1. The critical leaf K concentration to reach 95% of the maximum yield was 29.3 g K kg−1, but there was an extreme increase in the tuber yield even with K rates that provided leaf K concentrations above this limit. Potassium fertilization increased the firmness and reduced soluble solids and protein in tubers.Core Ideas K is the nutrient that is most taken up and removed by the potato crop. In clay soils, the splitting of K fertilization has little influence on potato tuber yield and quality. K fertilization increases tuber yield more, and up to higher rates in soil with low K concentration. K fertilization increases the tuber firmness, but reduces the soluble solids and protein concentration.

Does winter oilseed rape as a winter cover crop influence potato late blight development in an organic crop rotation?

ABSTRACTIn this study, the effects of a winter cover crop (CC) and its combination with composted cattle manure (CC-M) on the development of potato late blight (Phytophthora infestans) and crop yield were investigated and compared with a system with no cover crop (NC). In the CC and CC-M systems, winter oilseed rape (Brassica napus L) was used as the winter cover crop before potatoes. The hypothesis that the cover crop could be used as a possible control strategy against late blight in organic potato cultivation was not confirmed. Although the progression of foliar late blight damage in CC treatment was significantly slower in the early stages of disease development relative to NC, CC did not significantly reduce late blight at the later stages, or over the full season, and it did not increase tuber yield. Adding cattle manure to the CC treatment favoured late blight development and the damage was significantly more severe than in the other systems and tuber yield was nominally lower (though not significantly). The late blight pressure differed between treatments, with early disease development significantly slower on CC plots compared to CC-M in both growing seasons, but still not different to that in the plants grown in the NC system. Based on the results, in regions where oospores are a primary infection source, making P. infestans a soilborne pathogen, the use of cover crops may provide a sustainable strategy for reducing late blight damage in an organic system, but further investigation is needed.

Effect of nitrogen and phosphorus fertilization on growth components, yield and tuber quality characteristics of two potato cultivars grown under organic production system

The effect of two levels of nitrogen (Ν1=1.3 and N2=2.0 g Ν plant(‑1)) and two levels of phosphorus (P1=3.1 and P2=5.2 g P(2)O(5) plant‑1) on the growth, yield and tuber quality of two potato cultivars (‘Voyager’, ‘Spunta’), grown during spring season at Kalamata, Greece was studied. Seed tubers were planted in 11-L pots containing a mixture 1:1 (v/v) of peat (pH=6, no additional inorganic nutrient elements) and perlite. In all plants the same amount of PatentKali (0-0-30 + 10% MgO + 42% SO(3)) was applied (6.6 g K(2)O and 1.3 g MgO plant(‑1)). In order to meet the fertilization treatments, the organic fertilizers Biosol (7-0.5-0.3), Phosphorite (0-27-0) and Acadian 1-1-16 were used. In both cultivars, the higher N-dose increased the fresh weight of leaves, shoots, tubers, and shoot N-content. It also increased N-content of tubers when phosphorus was applied at the lower dose. In both cultivars, the higher P-dose increased the fresh weight of shoots, tubers N-content when nitrogen was applied at the lower dose. Phosphorus did not affect tuber yield in ‘Spunta’, but in ‘Voyager’, the higher P-dose increased tuber yield. In addition, the higher P-dose increased leaf N-content in ‘Voyager’ when nitrogen was applied at the lower dose. However, fertilization treatments did not affect dry matter content, P-content and K-content of leaves, shoots and tubers. We concluded that, in organic farming system, tuber yield is favoured by nitrogen fertilization in both ‘Spunta’ and ‘Voyager’ and by phosphorus fertilization in ‘Voyager’, however, tuber quality characteristics were not affected by nitrogen or phosphorus fertilization.

Irrigation and Nitrogen Fertilizer Rate Impacts on Soil Nitrate in Potato Production

ABSTRACTParts of the Kern County have high nitrate levels in groundwater. A State Water Resources Control Board commissioned report has indicated that crop land agriculture is the main source of nitrates in the groundwater. Annual rainfall is less than 20 cm, thus irrigation is necessary for optimum crop production. A project was undertaken to evaluate current nitrogen fertility and irrigation scheduling in potato production and their contribution, or lack thereof, to nitrate movement in the soil profile and potential nitrate contamination of groundwater. A line-source sprinkler plot area was established to create soil moisture regimes of 120% of target, target (optimum soil moisture for potato growth) and 80% of target. Pre-plant and post-harvest soil samples were collected to a depth of 2 meters. Plant, root and tuber samples were collected and analyzed for nitrogen content. Soil moisture and irrigation amounts were monitored. Plant dry matter and tuber yield increased with each N rate increase. The high N rate increased plant growth disproportionally to the increased tuber yield. Appropriate irrigation scheduling did not produce water movement beyond the effective potato rooting zone. Excessive irrigation moved soil nitrate deeper into the soil profile.

Productivity and establishment of DRIS indexes for cultivation of potato cultivar Asterix tubers in a dystrophic Red Latosol

The potato culture has the highest relative demand for fertilizers per unit area, around 2.3 to 2.8 t ha-1. The objective of this study was to evaluate the productivity of a potato Asterix cultivar subjected to different doses of nitrogen, phosphorus, and potassium, and to establish the DRIS index according to productivity results. The experimental design was randomized blocks, with 5 rates and 4 replicates for each nutrient totalizing 20 plots per experiment. The rates of nutrients were: nitrogen (0, 70, 140, 210 and 240 Kg ha-1); phosphorus (0, 200, 400, 600 and 800 kg ha-1) and potassium (0, 150, 300, 450 and 600 kg ha-1). For leaf diagnosis by the DRIS index, 10 complete leaves of the third expanded trifoliate were collected. The DRIS standards calculations were based on populations of high productivity (or reference) and low productivity. Plants whose productivities were greater than 22 t ha-1 represented the groups of reference. It was concluded that productivity was not influenced by the P and K doses studied, with an increase in yield of tubers as a function of the N rates applied, up to the dose of 173 kg ha-1 of N. According to the DRIS index, it is possible to establish the order of limiting nutrients for failure in descending order in areas with high productivity Ca&gt; Mn&gt; P&gt; S&gt; Zn = Cu&gt; K&gt; N&gt; B&gt; Fe&gt; Mg, and the order of limiting nutrients in areas of low productivity Ca&gt; Cu&gt; Mg&gt; P&gt; S&gt; Mn&gt; Zn&gt; K&gt; Fe = B&gt; N. The results showed that productions above 22 t ha-1 need adjustments of the soil fertility managements.

Variations in Stolon Length and Tuber Roots Among Six Potato Cultivars

This study is tested whether the stolon length and tuber roots show variations and could affect potato yield among the potato cultivars over two cropping seasons. Six potato cultivars from a group of improved and local cultivars were examined. The results of the experiments done during both seasons revealed that the stolon length and tuber roots showed variations within and among cultivars. Also a relationship between the length of the stolon and yield of tubers was found. The strongest correlations involved from the stolon length and the tuber roots with the increase in tuber yield under the improved cultivars, then the local cultivar with the decrease in yield. These correlations were positive: the higher the value of the parameter, the greater the observed increase in yield with improved cultivars. This showed a relationship between stolon length and tuber roots with the increase of yield; this relationship was stronger for roots in improved cultivars than in the local cultivar. Therefore, this study indicates that improved potato cultivars with deep root systems might improve tuber yields in eastern highlands of Ethiopia.

A Rhizosphere-Derived Consortium of Bacillus subtilis and Trichoderma harzianum Suppresses Common Scab of Potato and Increases Yield

The ability of a rhizosphere-derived microbial product (composed of a consortium of a strain of Bacillus subtilis and a strain of Trichoderma harzianum) to suppress common scab disease in potato caused by Streptomyces spp. was examined over a two-year period. Relative to the condition in which 0 kg·ha−1 of the designated microbial product was applied (control), the disease index decreased by 30.6%–46.1%, and yield increased by 23.0%–32.2% in treatments in which 225 or 300 kg·ha−1 of the microbial product was administered, respectively. The bacterial communities present in the rhizosphere were assessed at an early stage of tuber formation, a time at which tubers are susceptible to common scab. Potato plants in which soils were treated with 225 or 300 kg·ha−1 of the microbial product harbored rhizospheric microbiota with lower α-diversity and an increased relative abundance of taxa representing the beneficial bacteria. In summary, a select microbial product composed of a consortium of Bacillus subtilis and Trichoderma harzianum effectively suppressed common scab disease and increased tuber yield by establishing a high relative abundance of beneficial bacteria in the rhizosphere.