Phosphorus Dynamics in Potato Plants

Phosphorus is present in plants in both the inorganic, as orthophosphate, and organic forms. The organic farms are compounds in which the orthophosphate is esterified with hydroxyl groups of sugars and alcohols, or bound by a pyrophosphate to another phosphate group (4). These organic forms are especially Important for energy storage and transfer processes. In P deficient plants, the Inorganic P concentration Is depressed much more than the organic P concentration. This reduction Is accompanied by reduced protein synthesis and reduced vegetative growth, particularly root growth. Phosphorus is relatively mobile in plants and, under conditions of P deficiency, Is translocated from the older plant tissues to the actively growing tissues or to plant parts that serve a storage function. Phosphorus deficiency symptoms are generally expressed in the older leaves as a darkish green color from an enhanced anthocyanin production. Plant nutrient analysis is used to determine the nutritional status of the plant, reflecting the nutrient availability in the soil. Important factors influencing the nutrient concentration and uptake are plant age, plant parts or tissues analyzed, and the availability of other nutrients. Petioles from the fourth leaf from the growing tip are generally used as Indicators of nutrient status In potato plants. Critical nutrient ranges for N, P, K, Zn, and Mn are available for use in the Pacific Northwest growing areas (2). Most of these data for potatoes were developed by relating nutrient concentrations during plant growth to final tuber yields. Recent studies show that N fertilizer efficiencies and crop yields are improved if the N fertilizer is applied according to crop growth rates (7, 8). In that study petiole NO?-N concentrations were used to monitor the plant's N nutritional status. This project is an attempt to apply some of the same concepts and principles to the P nutrition of this crop. The objectives of this report are to relate the petiole P concentrations to the P and dry matter distribution patterns during potato plant development and to relate these changes to final tuber yields

Nitrogen Requirements of Potatoes

Nitrogen fertilizer applications, for maximum fertilizer efficiencies and crop yields, should be based on the N required by the crop during its various growth stages. The objectives of this paper were to identify the N requirements of the potato plant (Solanum tuberosum L.) during growth and to evaluate selected soil and plant tissue tests as indicators of the plant's N status. Growth analysis data and soil and petiole NO3-N concentrations were obtained at predetermined time intervals from N fertilization treatments in replicated field studies on a coarse-silty mixed, mesic Durixerollic Calciorthrid soil. Maximum early tuber growth occurred when leaf area index was between 2.5 and 3.2 and the tops contained between 79 and 100 kg N ha-1 at the start of linear tuber growth. A preplant N fertilizer application between 67 and 134 kg ha-1 gave these characteristics under the experimental conditions. The maximum dry matter production rate per day (approx. 250 kg ha-1) occurred when there was between 80 and 140 kg N ha-1 in the plant tops and roots. An average tuber growth rate of 0.75 Mg ha-1 day-1 required a N uptake rate of 3.7 kg ha-1 day-1 to prevent the loss of N and dry matter from the tops and roots. Sufficient N was available for this rate when the soil NO3-N concentration was > 7.5 mg kg-1 (0.46-m soil depth), corresponding to 15 000 mg kg-1 NO3-N in the fourth petiole. Soil and petiole NO3-N concentrations may be used to adjust the N fertilization rates during the growing season. This practice has the potential of increasing the overall N fertilizer use efficiency and final tuber yields within the climatic, disease, and variety limitations

RuP2 Pool Size Indicated by CO2 Assimilation Following the Abrupt Loss of Light

Measurement of the changes in CO2 uptake by single leaves following the abrupt onset of darkness were made on sugarbeets (Beta vulgaris L.) and (Phaseolus vulgaris L.) The shape of the CO2 dark response curve was analyzed with respect to the reaction kinetics of CO2 RuP2 and RuP2 carboxylase. It was concluded that the net uptake of CO2 in the dark from a 1% O2 atmosphere can be approximately related to the pool size of the RuP2 substrate in the chloroplasts of C3 plants. This information was combined with CO2 levels and decay rates of the response curves to infer changes in carboxylase activity. Preliminary data are presented showing the relative concentration changes in RuP2 as light intensity decreases and as water stress increases. The method may prove useful in studies of plant response to environmental stresses

Phosphorus Relationships in Potato Plants

Maximum potato (Solanum tuberosum L.) tuber yields occur when an active plant canopy is maintained until normal plant maturation. Plaid nutrient concentrations and uptake rates play a major role in maintaining an active plant top. The objectives of this study were to relate the plant P concentrations to the P and dry matter balance between tuber and total plant growth needs. Growth analysis data, plant and leaf total P concentrations and content, and the petiole soluble P concentrations were obtained on a 10-to 14-day sampling interval from P fertilization treatments in replicated field studies. The P concentration of the plant tops was significantly related to the petiole soluble P concentration and the P concentration of the active leaves. Total plant P uptake and dry matter production rates were not adequate for the tuber growth rate when the total P concentrations of the tops and active leaves were less than 2.2 g P kg-1. Soluble P concentrations in the fourth petiole down from the growing tip were less than 1000 and 700 mg kg-1 when P uptake and dry matter production rates were not adequate for tuber growth, respectively. Final tuber yields increased from 30 to 70 Mg ha-1 as the number of growing days past tuber set increased from 10 to 60 days for which the P concentration of the tops was above 2.2 g P kg-1. The petiole soluble P concentration decreased during the growing season following a semi-logarithmic relationship. This relationship enabled the prediction of the petiole soluble P concentration for the rest of the growing season and could be used to predict when to apply supplemental P fertilizer

Nitrogen Sources for Bean Seed Production

Beans (Phaseolus valgaris L.) often respond to N fertilization; however, N fertilization is not practiced for maximum seed production in southern Idaho. This suggests that the symbiotic relationship and/or soil N sources can provide most of the N needed by this legume. Our objective was to evaluate the relative contribution of the symbiotic-nonsymbiotic N sources by studying the effects of N fertilization on the symbiotic N? fixation and seed yields under field conditions. Experiments were conducted on silt loam soils belonging to the Portneuf series (Xerollic Calciortnids). An acetylene reduction (AR) method was used to determine the effect of N fertilization treatments on the relative seasonal Ng (AR) fixation. The symbiotic N? fixation was also estimated by the equation, N? = Nup — (Nl + Nm - Nh) — ?Nf, where Nup is the accumulated N uptake measured near physiological maturity, Nl and Nh are the amounts of soil NO?-N in the root zone before planting and near physiological maturity, Nm is the N mineralized from soil organic N sources, and ? is the recovery of the N fertilizer (Nf) applied. Estimates of the N fertilizer recoveries were obtained from two experiments using 15N-depleted (NH?)?SO?. The symbiotic N? relationship contributed up to 90 kg N/ha, which was 40 to 50% of the total N found in bean plants near physiological maturity. The amount of symbiotic N? fixed decreased as the available soil N or fertilizer N increased, and increased as the N required by the individual cultivars increased. The response to N fertilization depended upon the cultivar, as well as on the N available from soil sources. Measured fertilizer N recoveries ranged from 7 to 33%. An average of 52% of the total N uptake near physiological maturity was taken up after the maximum symbiotic Ng(AR) rate occurred; while the seed contained an average of 60% of the total N uptake. A low N fertilization rate (< 50 kg N/ha) when the soil Nl was low (<50 kg N/ha) ensured an early vigorous plant growth but did not always increase seed yields. Higher N fertilization rates may be required on soils with lower amounts of mineralizable N

Dry Matter Production and Nitrogen Utilization by Six Potato Cultivars

The rate and duration of tuber growth largely determines the final potato (Solanum tuberosum L) tuber yields. Cultivars that continue leaf development and nutrient uptake while maintaining maximum tuber growth rates may have higher final tuber yields, yet different N requirements. The objective of this study was to obtain information relating plant growth rates to N availability for selected potato cultivars. Total dry matter accumulation, and N assimilation patterns of indeterminant cultivars, 'Russet Burbank', 'Lemhi Russet, 'Centennial Russet', and one advanced selection A66107-51, were compared-with that of two determinant cultivars 'Pioneer' and 'Norgold Russet', at three N levels. Cultivars were grown in a field experiment on a Portneuf silt-loam soil (Xerollic Calciorthids). High available soil N levels at planting delayed the linear potato tuber growth period 7 to 10 days but had minor effects on the time of tuber initiation for the indeterminant varieties. Maximum tuber growth rates (tuber bulking) were 900 to 1,300 kg/ha/day. A66107-51 was superior in N-use efficiency to the other cultivars. Between 70 and 100% of the total available N was utilized by this cultivar in producing high yields. This information may be used to select lines and cultivars that will optimize production. A knowledge of plant growth and N uptake rates can improve the fertilizer recommendations for each cultivar

Nitrogen fertilizer efficiencies on potatoes

Nitrogen fertilizer efficiencies must be known to successfully apply N fertilizer according to crop growth needs. The objective of this study was to determine the recovery, partitioning, and translocation of N fertilizer applied at different times for potato production. Russet Burbank potatoes were fertilized preplant with 15N-depleted ammonium sulfate, and during early and late tuber growth with urea containing K15NO3 in 1978 or (15NH2)2CO in 1980. All N applications increased tuber yields above the control treatments. The N recovery efficiency was 60% for the preplant N application, and over 80% and near 60% for the N applications during tuber growth in 1978 and 1980, respectively. Good agreement was found between the isotope and difference methods of determining N recovery efficiencies. Labeled N was initially concentrated in the stems and leaves, particularly if applied during tuber growth. Over 80% of the assimilated, labeled nitrogen was found in the tubers at the start of plant maturation. These data indicate that a significant improvement in N fertilizer efficiency would result from split N fertilizer applications made according to crop growth needs

Specific gravity of Russet Burbank potatoes

Variability in specific gravity of Russet Burbank potatoes was documented in a single 32 hectare field. Maximum variation was 40 units among individual tubers within hills (one unit equals one part in 1000th of specific gravity measurement) and 15 units among hills. Field site variability of 10-15 units was common between sampled grid lines in the field; but bulked samples (truckloads) reduced the sampled variability to 8-10 units. When the samples were taken from bulked lots as opposed to single hill samples, the variability decreased. Grower lots, which were pooled samples from several truckloads, showed specific gravity differences of 2-7 units even though all lots were from the same field. These variations among specific gravity samples should be taken into account when considering total solids content in any lot of potatoes. Degree of russetting of the skin and hollow heart also influenced specific gravity measurements. Measured differences between peeled and unpeeled lots of 10 units in specific gravity corresponded to 2% difference in total solids content. Statistically, the variance of the peeled lot was one half that of the unpeeled lot, therefore, to minimize the measured differences due to skin type, peeled potatoes could be used for the specific gravity measurements

Growth analysis in the potato crop under different irrigation levels

Conduziu-se um experimento na Fazenda São Manoel, localizada em São Manuel, SP, pertencente à Faculdade de Ciências Agronômicas da Universidade Estadual Paulista, com o objetivo de avaliar os efeitos de diferentes lâminas de irrigação no crescimento da cultura da batata (Solanum tuberosum ssp. tuberosum), cultivar Aracy. O ensaio foi instalado em um Latossolo Vermelho-Escuro, textura arenosa, sob uma cobertura de plástico. O delineamento experimental utilizado foi o de blocos ao acaso, com cinco tratamentos, cinco coletas de plantas para fins de análise de crescimento, e quatro repetições. Os tratamentos consistiam em irrigar a batata quando a tensão da água no solo atingia 15, 35, 55, 75 e 1.500 kPa. O aumento nas lâminas de irrigação induz incremento no índice de área foliar, na duração da área foliar, na taxa de crescimento relativo e na taxa assimilatória líquida. _________________________________________________________________________________________ ABSTRACT: An experiment was carried out at Fazenda São Manoel, pertaining to the Faculdade de Ciências Agronômicas of the Universidade Estadual Paulista, São Manuel, SP, Brazil, to evaluate irrigation levels in the potato (Solanum tuberosum ssp. tuberosum) growth, cv. Aracy. This work was installed in a sandy Dark-Red Latosol, under a plastic cover. The experimental design was an entirely randomized block composed by irrigation in the potato plots when the soil water potential has reached 15, 35, 55, 75 and 1,500 kPa, and five plant sampling time with four replicates. It was found that higher irrigation levels led to increase of the leaf area index, leaf area duration, relative growth rate and net assimilation rate