Tuber Dry Weight Research Articles

Effect of Liquid Organic Fertilizer and Cuttings of Bulbs on Growth and Production of Shallots (Alium Ascalonicum L.)

The aim of this study was to determine the effect of the concentration of liquid organic fertilizer and seed tuber cutting against to growth and production of onion. Experiment was arranged in a factorial experiment using a randomized block design (RBD) and repeated 3 times. Factorial I was concentrationof liquid fertilizer comprises four levels: 0,2.4, and 6 cc/liter of water; factor II was piece of tuber shoots comprises 3 levels: no cutting, cutting 1/4 and ½ part cutting the tubers sprout. The measured variables were plant length, number of leaves, number of tillers, root length, weight stover, fresh weight and dry weight of tubers. Data were analyzed by ANOVA followed by a test ynag HSD 5%. The results showed concentration of organic fertilizer influence on the plant long parameter age of 14, 21 and 28 days after planting, and the number of leaves at the age of 14 and 21. Cutting seed tubers affect the number of leaves aged 14, 21 and 28 days after planting. There is an interaction effect between kosnetrasi organic liquid fertilizer by cutting the tubers lip on the length of the plant ages 35, 42 and 49 days after planting, the number of leaves of the plant ages 28, 35, 42 and 49 days after planting, and the panang roots, weights stover, fresh weight and dry weight of tubers red onion. Combination treatment liquid fertilizer concentrations of 6 cc/liter and ½ part cutting buds bulbs given the best results.

PERTUMBUHAN DAN PRODUKSI BAWANG MERAH (Allium ascalonicum L.) BERBASIS APLIKASI BIOURINE SAPI

ABSTRACT The research aims to assess the response to the growth and production of onion against of liquid organic fertilizer from cow biourie in some concentrations and to get the best concentration for the growth and production of red onion. The research was conducted atfield experimental in Pandu, North Minahasa regency from May to July 2014. The experiment was designed using a randomized block design. The treatment was concentration of cow biourine namely 0% (B1) 10%, (B2) 20%, (B3) 30%, (B4) 40% and (B5) 50%. Each treatment was replicated three times. Characters observed were plant height, number of leaves, tuber diameter, number of tuber, fresh weight of tuber with leaves and dry weight of tuber. Data was analyzed using analysis of variance. The result showed that the biourine concentration had significant effect on plant height, number of leaves, tuber diameter, number of tuber, fresh weight of tuber with leaves and dry weight of tuber. Treatment of B1, B2, B3 and B4 concentration were not significant difference at plant height. However, those four treatments were significantly different compared to B0 and B5. The fives treatment differed with the control on characters of number of leaves, number of tuber andfresh weight of tuber with leaves. On character of tuber dry weight, B2 treatment was significant difference compared to control whereas the other treatments were not significantly differed. On character of tuber diameter, three treatments were significant difference compared to the control namely B2, B4 and B5. Keywords : Allium ascalonicum L, biourine cow, fertilizer, growth and production

Responses of growth, physiological traits and tuber yield in Helianthus tuberosus to seasonal variations under tropical area

Seasonal variations affect growth and yield of a crop, primarily by changing its phenological developmental processes. The objective of the present study was to evaluate seasonal variation effects on growth and development of Jerusalem artichoke. The experiment was conducted during the early-rainy seasons in June–September 2011 and the post-rainy seasons in September–December in 2011, and two seasons were repeated in 2012 at the Field Crop Research Station of Khon Kaen University. A randomize complete block design (RCBD) with 5 replications was used. Four Jerusalem genotypes including JA 89, HEL 65, CN 52867 and KT 50-4 were used. Results indicated similar phenological development between the early and post rainy-seasons. However, high temperature combined with long photoperiod during the early-rainy seasons delayed tuber initiation and extended maturity. Low temperature and short photoperiod was a favorable condition for tuber development but reduced vegetative and reproductive development. On average, tuber dry weights and tuber growth rate were higher in the post-rainy season compared to the early-rainy season. On the other hand, biomass and crop growth rates were higher in the early-rainy seasons compared to the post-rainy seasons. The knowledge obtained in this study is important for Jerusalem artichoke production and selection of Jerusalem artichoke genotypes in the tropical climate.

Yield and yield components of minituber potato under direct cultivation and transplanting

This research was performed to study the effect of direct planting and transplanting of potato minituber on its yield and yield components. The experiment was designed as a randomized complete blocks with nine treatments and three replications. Treatments were one direct and eight indirect planting. In order to prepare the nursery, two types of pots (peat and nylon) and four types of substrates including sand + peat moss (1:1), sand + Kimiya organic fertilizer (1:1), sand + vermicompost (1:1) and sand + farm soil (1:1) were used. Results showed that there was significant difference in regard to mean yield per plant, mean wet weight of tuber, number of tubers smaller and greater than 80 g, percent dry weight of tuber, biologic yield, starch percentage and nitrate content of tubers. The highest mean tuber yield per plant, number of tubers greater than 80 gr and biologic yield belonged to plants in nylon pots with substrate of sand + Kimiya organic fertilizer. The highest percentage of starch and tuber dry matter belonged to plants in peat pots with substrate of sand + soil. The highest mean wet weight of tubers belonged to nylon pots with substrate of sand + peat moss. The highest number of tubers lower than 80 g and the highest nitrate content was obtained by direct planting. The sand+ Kimiya organic fertilizer, which provides the necessary elements for plant growth, with more yield and number of marketable tubers, could be the best substrate as compared to other substrates used in this experiment.

Root responses of Jerusalem artichoke genotypes to different water regimes

The objective of this study was to determine effects of drought on selected root growth parameters and develop relationships between root parameters and tuber yield for selected Jerusalem artichoke (JA) genotypes. Three water regimes (Field capacity, 50% available soil water (AW) and 25% AW) and five JA varieties (JA 60, JA 125, JA 5, JA 89 and HEL 65) were planted with factorial treatments in a randomized complete block design with four replications. Data on root dry weight (RDW) and root: shoot ratios (RSR) were measured manually. Root diameter (RD), root length (RL), root surface area (RSA) and root volume (RV) were collected at harvest. Drought tolerance indices (DTI) were calculated for all root parameters. Drought reduced all root parameters and DTI but increased RSR in JA 60, JA 125, JA 5, and HEL 65. JA 125 had high values for all root traits and DTI of these traits under drought stress. JA 60 had high DTI of RDW, RD and RSR under mild and severe water stress. JA 5 had high DTI of RDW, RD, RL, RSR and RV under drought conditions. JA 89 and HEL 65 performed well for RDW, RD, RL and low DTI of all root characteristics. DTI for root parameters were positively correlated with tuber dry weight under mild and severe water stress. The JA 5, JA 60 and JA 125 varieties showed high DTI for some root traits, indicating that better root parameters contributed to higher tuber yield under drought stress.

The importance of arbuscular mycorrhiza for Cyclamen purpurascens subsp. immaculatum endemic in Slovakia.

At present, there is no relevant information on arbuscular mycorrhiza and the effect of the symbiosis on the growth of wild populations of cyclamens. To fill this gap, two populations of Cyclamen purpurascens subsp. immaculatum, endemic in Nízke Tatry (NT) mountains and Veľká Fatra (VF) mountains, Slovakia, were studied in situ as well as in a greenhouse pot experiment. For both populations, mycorrhizal root colonization of native plants was assessed, and mycorrhizal inoculation potential (MIP) of the soils at the two sites was determined in 3 consecutive years. In the greenhouse experiment, the growth response of cyclamens to cross-inoculation with arbuscular mycorrhizal fungi (AMF) was tested: plants from both sites were grown in their native soils and inoculated with a Septoglomus constrictum isolate originating either from the same or from the other plant locality. Although the MIP of soil at the NT site was significantly higher than at the VF site, the level of AMF root colonization of C. purpurascens subsp. immaculatum plants in the field did not significantly differ between the two localities. In the greenhouse experiment, inoculation with AMF generally accelerated cyclamen growth and significantly increased all growth parameters (shoot dry weight, leaf number and area, number of flowers, tuber, and root dry weight) and P uptake. The two populations of C. purpurascens subsp. immaculatum grown in their native soils, however, differed in their response to inoculation. The mycorrhizal growth response of NT plants was one-order higher compared to VF plants, and all their measured growth parameters were stimulated regardless of the fungal isolates' origin. In the VF plants, only the non-native (NT originating) isolate showed a significant positive effect on several growth traits. It can be concluded that mycorrhiza significantly increased fitness of C. purpurascens subsp. immaculatum, despite the differences between plant populations, implying that AMF symbionts should be taken into account in conservation programs of this endemic plant.

Potato Crop Growth and Yield Response to Different Levels of Nitrogen under Chhattisgarh Plains Agro-climatic Zone

Field investigation was carried out to study the effect of different nitrogen levels on growth and yield parameters in potato var. Kufri Surya. The experiment was laid out in a randomized block design with treatments consisting of six nitrogen levels replicated four times. Growth parameters like plant height, number of leaves per plant, number of shoot per plant, fresh and dry weight of shoot per plant and yield attributing parameters like number of stolon, fresh and dry weight of tuber per plant increased with an increase in nitrogen levels with maximum values being obtained on application of highest nitrogen level (375 kg N/ha). However, highest values for number of tuber per plant and per plot as well as tuber yield per plot and per hectare was recorded on application of 225 kg N/ha. The highest net returns (Rs. 117323) and maximum B: C ratio (1.42) was recorded on application of 225 kg N/ha.

Diversity of crop development traits and nitrogen use efficiency among potato cultivars grown under contrasting nitrogen regimes

Potato (Solanum tuberosum L.) requires abundant nitrogen (N) to perform well and has low nitrogen use efficiency (NUE). We assessed phenotypic variation among 189 potato cultivars for NUE and the association between NUE and ecophysiological variables describing canopy development (CDv), under high and low N input. In 2009 and 2010, 189 cultivars were grown with N supply (soil N + fertiliser N) of 75 or 180 kg N/ha at Bant, the Netherlands. CDv was assessed weekly as the percentage of soil covered by green potato leaves (%SC). Data were analysed using a model that described CDv as a function of thermal time, based on the Beta function and estimates of cardinal temperatures. Nitrogen significantly affected model-derived, biologically relevant, curve-fit parameters for each cultivar. The t 1 (i.e., thermal time required to reach maximum soil cover (Vx)) was higher at low than at high N. Other parameters were higher at high than at low N, especially Vx and the period over which it was maintained. Nitrogen also affected tuber dry matter yield, tuber size and weight distributions, N content and N uptake but not tuber dry matter percentage. The total area under the %SC curve was highly correlated with yield in both years. Cultivars performing well under high N also performed well under low N. There was large variation in NUE component traits among cultivars; maturity type partially explained this variation. Variables of the CDv model captured this variation, N effects on light interception and its correlation with yield.

English

This study was done to determine the effect of initial node strength on dry matter yield of cassava. Studies were conducted at the Waterloo Research Campus, University of Trinidad and Tobago using the sets of Mexican variety (Mx) at 6 months with 1 to 3 nodes, 4 to 9 cm, and dry matter of 6 to 15 g/set. The crop was established at 60 × 80 cm and treated with a compound NPK fertilizer. Growth analysis (functional approach) was carried from 20 to 340 Days after emergence (DAE), and the best fit polynomial regression applied. The results indicated that tuberization started after 120 DAE and tuber dry weight increased with increasing set size (YTDW = -1177 + 9.90D - 1.26-2 D2 + 37.7N2). The 3 node sets produced (P > 0.05) the highest tuber yield. The leaf area ratio (LAR) showed (P > 0.001) a quadratic response (Ylar = 12.8 - 1.94 H - 2.39 N + 0.08 H2 + 0.18 N*H), peaked at 2 g/cm2/day1, and declined at harvest. Both the net assimilation rate (NAR) and the relative growth rate (RGR) were not affected by the number of nodes, however, the NAR peaked 0.046 g/m2/day at 60 DAE. The initial strength of 3 nodes sets proved to be superior to the single node sets. Key words: Cassava, growth analysis, tuberization, nodes, sets.

Ex-Situ Conservation and Selection of Superior Genotypes Through Trait Association Studies in Asparagus racemosus

An experiment consisting of twenty seed sources of Asparagus racemosus was planted in randomized block design with three replications during February 2007 at Forest Research Institute Dehradun, India. Observations were recorded at the age of two and half years to assess them for various growth parameters to know association pattern for trait of economic interest for formulation of suitable selection strategy for genetic improvement. Correlation coefficients suggested that shoot dry weight, maximum shoot height, number of tubers, number of shoots and tuber length had positive and highly significant association with tuber dry weight, hence tuber dry weight can be increased indirectly through these correlated characters. Positive correlation may be attributed to the coupling phase of linkage. Path coefficients at genotypic and phenotypic level revealed that the maximum positive direct effect on tuber dry weight was exerted by shoot dry weight. However, maximum shoot height, tuber length, number of shoots and number of tubers through shoot dry weight have high order positive indirect effect on tuber dry weight. It is clear from estimates of correlation coefficients that above cited traits have significantly positive associations. It is suggested that during formulating selection strategies higher tuber yield weightage should be given to these traits.

Genotypic variability for tuber yield, biomass, and drought tolerance in Jerusalem artichoke germplasm

Jerusalem artichoke could be an alternative feedstock for bioenergy during times when there are shortages of other raw materials for the ethanol industry. However, insufficient water under rainfed conditions is a major cause of Jerusalem artichoke losses. Genetic variation for drought tolerance is an essential prerequisite for the development of Jerusalem artichoke cultivars with improved drought tolerance. The objectives of this study were to determine the effects of drought stress on tuber dry weight and biomass and to investigate the genotypic variability in Jerusalem artichoke germplasm. The line-source sprinkler technique was used to compare moisture responses of a range of 40 Jerusalem artichoke genotypes grown using 3 water levels. Experiments were conducted on a Yasothon soil series in Northeast Thailand during 2010/11 and 2011/12 and included extended dry periods. Drought reduced tuber dry weight and biomass, and the reductions in tuber dry weight and biomass were greater under severe drought than moderate drought conditions. Over both seasons, CN 52867, HEL 53, HEL 231, HEL 335, JA 76, HEL 65, and JA 102 × JA 89 (8) had consistently high tuber dry weight (1.3 to 4.5 t ha -1 ) and HEL 53, HEL 61, HEL 231, HEL 335, JA 76, JA 15, JA 89, HEL 65, HEL 256, and JA 102 × JA 89 (8) had consistently high biomass (2.0 to 6.8 t ha -1 ). These Jerusalem artichoke genotypes are promising parents in breeding for drought tolerance.

Agronomical Evaluation of Aerial Yam/ Dioscorea bulbifera/ Accessions collected from South and Southwest Ethiopia

The experiment was conducted at Jimma Agricultural Research center. The objectives of the study were to estimate the level of diversity within collected accessions based on key agronomic trait(s) that can be used for selection of aerial yam accessions for high root yield and evaluate the accessions based on root yield and other related trait. A total of 47 accessions of aerial yam were tested in randomized complete block design with three replications. Both qualitative and quantitative data collected were subjected to multivariate analysis using principal component (PCA), cluster analysis and analysis of variance to determine the variability of accessions. The results of PCA based on qualitative traits indicated that traits have good contribution to the variability. The two-dimensional plot of the first two PCs showed a separation between accessions in big sized. Cluster analysis based on qualitative characters showed the creation of six distinct groups with different sizes and presence of variability, based on their above and below ground plant parts. The result of Shannon-Weaver diversity index (H’=0.18) showed low levels of diversity between aerial yam accessions. Analysis of variance indicated that tuber length, tuber diameter and vine length have highly significant (P>0.01) differences exists for most of the characters studied. Estimate of phenotypic and genotypic coefficients of variation also showed the presence of variability among the accessions for the a limited number of the characters namely, vine length, vine dry weight, tuber length and tuber diameter. Relatively high phenotypic (53.96, 44.99 and 26.07 %) and genotypic coefficients of variation (12.44, 22.81 and 11.18%) were observed for vine dry weight, tuber dry weight and vine fresh weight in the order of magnitudes. Heritability (39.69% and 25.70%) coupled with genetic advance as percent of mean (12.42% and 23.83%) were recorded for vine length and tuber dry weight per plot, respectively. Path coefficient analysis revealed that that vine dry weight (p =1.203) and leaf length (p =1.1949) was more important than other traits, hence can be used as a criterion for indirect selection. Therefore, selections based on vine dry weight and leaf length are vital to increase the yield and the genetic improvement of this crop. The overall results of this study showed that aerial yam accessions collected from south and southwestern Ethiopia have an enormous wealth of traits variation, indicating huge potential for its genetic improvements through selection and hybridization.

감자 고랭지 재배 시 표고 및 파종시기에 따른 괴경의 비대반응

ABSTRACT Field experiments were carried out to improve the cultural practice of potato by analysing its tuberization patterns. Tuberization patterns affected by different altitudes was analyzed at two potato cultivation regions, Jinbu (600 m) and Daegwallyung (800 m) using two potato cultivars, ‘Superior’ and ‘Atlantic’. To analyse tuberization patterns affected by different planting time, seed potatoes were planted at every 10 days from April 19 to May 19 in Daegwallyung. Total dry weight was greater in plant grown at the altitude of 800 m than 600 m during the entire growth period and the highest increase was observed at the early growth period, July 6, comparing to other growth period. The total dry weight was the greatest at 110∼112 days after planting (DAP) at the altitude of 800 m and 108～111 DAP at 600 m. There was no significant differences between altitudes and between cultivars. Tuber dry weight per plant at the altitude of 600 m was lower than 800 m on July 6 (58 DAP), but it increased rapidly from July 21 (73 DAP). At both altitudes, the increase of tuber dry weight per plant from July 6 to August 8 was higher than the other growth period. The time of growth period at which tuber dry weight per plant was the highest was similar at both altitudes that was 118～125 DAP at the altitude 800 m and 118～124 DAP at the altitude 600 m. Dry weight per tuber at the altitude 800m was higher than 600 m due to the number of tubers per plant. A higher increase of crop growth rate (CGR) was shown at the altitude 600 m on July 6 (58 DAP), comparing to at 800 m. The highest tuber dry weight per plant of each cultivar was shown when the planting time was April 29 for ‘Superior’ and was April 19 for ‘Atlantic’. Both the tuber dry weight of plant and the total dry weight were lower at a later planting time. Dry weight per tuber increased quickly during the period between June 30 to August 8. Tuberization period was shortened as the planting time was delayed.

Seasonal light interception, radiation use efficiency, growth and tuber production of the tuber crop Plectranthus edulis

Plectranthus edulis (Vatke) Agnew (Lamiaceae) is an ancient Ethiopian crop that produces below-ground, edible tubers on stolons. It is grown from seed tuber pieces. There is thus far little quantitative information on dry matter production of this crop and parameters determining growth and yield. The objective of this study was to understand and quantify the growth of P. edulis, and identify the processes determining and limiting yield. Two similar experiments were carried out at two sites (Awassa and Wondogenet in southern Ethiopia) in a split-plot design with five blocks and cultivar (Lofuwa and Chankua) as main factor and sampling date [20 2-weekly sampling dates from 14 to 280 days after planting (DAP)] as split factor. The crop was unknown at the start and showed an unusual growth pattern, for which reasons growth was analysed at a basic level.Maximum tuber weights were achieved 238 DAP in both cultivars and at both sites, and we consider the period up to 238 DAP as the growth period and the remaining time until the last sampling as the period of in situ storage, as is common farmers’ practice. Tuber dry weights at 238 DAP were c. 900–1000gm−2 and tuber dry matter concentrations 19–21%, corresponding to c. 4.5–4.9kgm−2 fresh tuber yield. Two processes limited the dry matter production: radiation interception by the crop and the conversion of the intercepted radiation into dry matter.Only about one third of the incident radiation was intercepted by the green leaves due to late emergence (c. 4 weeks), a slow development of the canopy after emergence until full ground cover was attained (c. 20 weeks), a short period during which ground cover was complete (c. 2 weeks) and a long period of declining ground cover starting 8 weeks before the end of the growing period.The radiation use efficiency (RUE) was established for the crops in Wondogenet and was only 1.59gMJ−1 PAR, on average across sampling dates. RUE varied across the growing period, increasing after emergence until early after tuber formation to about 2.7gMJ−1 PAR, then again decreasing because of a temporary stagnation (cv. Chankua in Awassa) or decrease (all other cultivar×site combinations) in total crop dry weight, starting 168 DAP in Awassa and 182 DAP in Wondogenet and lasting several weeks. During this period crop biomass decreased because the loss in canopy dry matter – especially stem dry matter – was not yet compensated for by an increase in tuber dry matter. Later, tuber production more than outweighed the decrease in canopy dry weight, and total dry weight and RUE increased again. During this last period the green stems might have significantly contributed to crop photosynthesis. The relative allocation of the total dry matter produced to the tuber varied between 81 and 99% at 238 DAP. Keeping the tubers in the soil after 238 DAP reduced tuber dry weights by 37–54% in 6 weeks.

RESPONSE OF POTATO PLANTS GROWN IN CLAY SOIL TO ANHYDROUS AMMONIA RATES AND FOLIAR APPLICATION OF ZN AND MN

Two Field experiments on potato (Solanum tuberosum, L. cv.Diamont) crop were carried out at El-Qanater Horticultural ResearchStation, Kalubiya, Governorate, Egypt located at lat. 30.11, long 31.60and 14.00 m above the mean sea level during two successive seasons2010 and 2011. The study concerned the use of different rates ofanhydrous ammonia (100 and 120 kg N/fed.) with foliar application ofzinc and manganese or both on potato crop in alluvial soil. Generally,in most cases,The high anhydrous ammonia level (120 kg N/ fed.) wasincreased significantly dry matter of potato plant at 90 days fromplanting and nitrogen & phosphorus content as well as dry weight oftuber/ plant (g/plant), fresh & dry tuber yield/fed., N, P, K, Zn and Mncontents of tuber compared to low anhydrous ammonia level (100 kgN/ fed.) of both seasons.Generally, the most parameters in this investigation wereincreased significantly when the treatment of foliar application withmixture of Zn and Mn was carried out in both seasons. In contrast, thelowest ones were recorded by the control treatment (without foliarspray) followed by sole foliar spray with Zn or Mn in two seasons.Finally, the best significant values of most parameters wereobtained by interaction between foliar application with mixture of Znand Mn under the high anhydrous ammonia level (120 kg N/ fed.).Meanwhile, the lowest ones were observed when control treatment(without foliar spray) with the low anhydrous ammonia level (100 kgN/ fed.) was practiced of both seasons.

The effects of introduction of a fungal glutamate dehydrogenase gene (<i>gdhA</i>) on the photosynthetic rates, biomass, carbon and nitrogen contents in transgenic potato

Glutamate dehydrogenase (GDH) catalyzes the reversible amination of 2-oxoglutarate with ammonium to form glutamate. GDH functions in nitrogen assimilation in microorganisms, such as Aspergillus nidulans. However, in plants, glutamine synthetase, not GDH, carries out nitrogen assimilation. Here, we report the eects of introduction of the gdhA gene, encoding NADP(H)-dependent glutamate dehydrogenase, from A. nidulans into potato. We analyzed the r esulting changes of photosynthesis, biomass, carbon and nitrogen contents under control and low-nitrogen conditions at theowering stage and the tuber-bulking stage. �ere were higher NADP(H)-GDH activities in GDH potato leaves than in the wild type. Regardless of nitrogen conditions, photosynthetic rates and soluble protein concentrations of leaves increased in GDH potatoes at theowering stage. High photosynthetic rates remained at the tuber-bulking stage in GDH potatoes. �e number and dry weight of tubers also increased in GDH potatoes. Under the low-nitrogen condition in particular, carbon and nitrogen contents of GDH potato tubers increased compared with those of the wild type. �is resulted from hig her rates of carbon and nitrogen redistribution to tuber in GDH potatoes than in wild-type potatoes. Ourndings show that the gdhA gene is a powerful tool to increase tuber dry matter and improve eciency of nitrogen use of potato.

Nitrogen and Potassium Fertilization Responses of Potato (Solanum tuberosum) cv. Spunta

A potato field experiment was conducted for 2 consecutive years to determine the effects of nitrogen (N) and potassium (K) fertilization rates on the yield and quality of potato cv. Spunta cultivated on soil low in N and K. A 3 × 4 complete factorial experiment was used with three rates of nitrogen (330, 495, and 660 kg N ha–1) and four rates of potassium (112, 225, 450, and 675 kg K2Ο ha–1). An additional treatment without fertilization was used as the control. On soils low in N and K, potatoes showed low yield response to K fertilizer. The greatest tuber yields for both years were achieved at 495 kg N ha–1 and 112 kg K2O ha–1 (29.81 t ha–1) and 225 kg ha–1 (27.13 t ha–1), respectively. Differences in mean fresh weight due to treatment application were not significant. Application of 495 kg N ha–1 significantly reduced harvest index (the ratio of tuber dry weight to the total dry weight at harvest) compared to 330 kg N ha–1, but at 660 kg N ha–1 harvest index achieved the greatest significant value. Potassium fertilization had no significant influence on harvest index. Nitrogen rates positively influenced the number of tubers. The addition of 450 kg K2O ha–1 significantly enhanced the number of tubers compared to the lower K rates, and the number was significantly decreased by the application of 675 kg K2O ha–1. Tuber dry-matter concentration was significantly promoted by N fertilization in both cultivation years, but it was negatively affected by K fertilization in the first year of cultivation. There was no change in tuber N with N application, but N application strongly increased nitrate (NO3) concentration, which fluctuated between 360 and 1382 mg kg–1 wet mass. Tuber NO3 was negatively correlated with tuber yield, indicating that high levels of NO3 in tubers can adversely affect yield. Tuber response to K fertilization was not in accordance with the rate of applied nutrient.

Evidence against sink limitation by the sucrose‐to‐starch route in potato plants expressing fructosyltransferases

To investigate whether the route from sucrose to starch limits sink strength of potato tubers, we established an additional storage carbohydrate pool and analyzed allocation of imported assimilates to the different pools. Tuber specific expression of the fructan biosynthetic enzymes of globe artichoke resulted in accumulation of fructans to about 5% of the starch level, but did not increase tuber dry weight per plant. While partial repression of starch synthesis caused yield reduction in wild-type plants, it stimulated fructan accumulation, and yield losses were ameliorated in tubers expressing fructosyltransferases. However, a nearly complete block of the starch pathway by inhibition of sucrose synthase could not be compensated by the fructan pathway. Although fructan concentrations rose, yield reduction was even enhanced, probably because of a futile cycle of fructan synthesis and degradation by invertase, which is induced when sucrose synthase is knocked out. The data do not support a limitation of sink strength by enzyme activities of the starch pathway but point to an energy limitation of storage carbohydrate formation in potato tubers.

Growth and yield response of potato crop to different sources of potash

Potassium out of macronutrients is very important for potato plant, as it regulates growth and vigour, improves quality and general health that ultimately hastens yield. Potassium also keeps potato away from various physiological disorder and infections. Organic matter like farm yard manure (FYM) improves potassium uptake by potato plants. A research project was planned to investigate the influence of different potash sources and their combination with FYM for enhanced growth and yield of potato. Results revealed that parameters like days to emergence, total emergence percentage, mortality percentage and number of stems per plant were significantly affected by potash source sulphate of potash. While number of tubers per plant and number of compound leaves per plant were significantly affected by the combination of ½ Murate of potash and ½ FYM. Plant height was found highest by the application of FYM. The yield parameters were found significantly higher by the combination of ¼ MOP and ¾ FYM. Tuber dry weight remained highest by the application of MOP alone and total soluble solids (TSS) were found boosted by the combined effect of ½ SOP and ½ FYM. In this way it is concluded that potash fertilizers with FYM can be a good policy towards obtaining higher yields of potato crop.

Growth and yield responses of sweet potato (ipomoea batatas) to time of potassium fertilzer application

Two field experiments were conducted at the Michael Okpara University of Agriculture, Umudike research farm in 2005 and 2006 wet seasons to determine the growth and yield responses of two sweet potato (Ipomoea batatas L. Lam) varieties viz TIS 87/0087 and TIS 8164 to time of potassium (K) fertilizer application in a humid forest zone of south eastern Nigeria. In 2005 cropping season, the experiment was a 2 x 4 factorial laid out in a randomized complete block design with four replications. Potassium (K) treatments comprised no K application, 100 kg K ha-1 at 4 weeks after planting (WAP), 100 kg K ha-1 at 8 WAP, 50 K ha-1 at 4 WAP + 50 K ha-1 at 8 WAP. Time of K application had no significant effect on the growth attributes of the varieties, except in tuber dry weight and total dry matter plant-1 at 16 WAP where it was higher with split K application at 4 and 8 WAP in TIS 87/0087. TIS 87/0087 was significantly (P < 0.05) higher in total tuber yield when 100 kg K ha-1 was applied at 4 WAP and also with split application at 50 kg K ha-1 at 4 WAP + 50 kg K ha-1 at 8 WAP. In 2006 cropping season, a 2 x 8 factorial in randomized complete block design with three replications was conducted at the same location as in 2005. The treatments comprised of no K application, 100 kg K ha-1 at 2 WAP, 100 kg K ha-1 at 4WAP, 100 kg K ha-1 at 6 WAP, 100 kg K ha-1 at 8 WAP, 50 at 2 WAP + 50 kg K ha-1 at 6 WAP, 50 kg K ha-1 at 2 WAP + 50 kg K ha-1 at 8 WAP and 50 kg K ha-1 at 4 WAP + 50 kg K ha-1 at 8 WAP. Tuber and total dry weights were highest when K was split applied at 4 + 8 WAP but lowest when it was applied whole at 8 WAP. TIS 87/0087 was significantly (P < 0.05) higher in tuber yield ha-1 when K was split applied at 2 WAP + 6 WAP or 50 kg K ha-1 at 4 WAP + 50 kg K ha-1 at 8 WAP. TIS 87/0087 which is a higher yielding variety is recommended for the study area with split application of K at 2 WAP + 6 WAP or at 4 WAP + 8 WAP.KEY WORDS: Sweet potato, Ipomoea batatas, K, time of K application.