Effects of potassium supply on growth and yield of safflower as compared to sunflower^§

Abstract

Safflower may have a certain production potential under German conditions, particularly in organic farming where the putatively low nutrient requirement is highly welcomed. However, current knowledge regarding the nutrient requirements of safflower as compared to similar oil crops is limited. It was thus the aim of this study to determine the growth and yield response of safflower (Carthamus tinctorius L.) as compared to sunflower (Helianthus annuus L.) with respect to potassium (K) supply. Three safflower and two sunflower plants were cultivated in 5 L Mitscherlich pots. Both species responded strongly to increasing K supply with respect to plant growth and yield. Growth and yield of safflower increased up to 1 g K per pot, while the optimum for sunflower was 3.0 g K per pot. Safflower out-yielded sunflower at low K supply, while at high K level, the opposite was observed. Supply of K affected virtually all yield components in both species, though to different degree. The number of capitula in safflower was only slightly affected, and the number of achenes per capitulum was only reduced under severe K deficiency, while single-achene mass increased with increasing K supply. In sunflower, the number of achenes per capitulum strongly responded to the K supply, as did the single-achene mass. Oil yield in safflower was affected by K deficiency mainly due to reduced achene yield, not oil concentration. However, oil yield in sunflower was severely affected by low K supply due to both reduced achene yield and lowered oil concentration. Multiple-regression analyses indicate that in sunflower, the stem dry matter (DM) and the total amount of K accumulated in the aboveground biomass were most important, while in safflower the total amount of K and N accumulated had the highest impact. It is concluded that sunflower is more sensitive to inadequate K supply than safflower.

Mechanisms of Phosphorous Uptake Efficiency of Safflower and Sunflower Grown in Different Soils

“…In agreement with our results concerning dry weight (Table 1) and fresh weight (Table 2), P nutrition was reported to have a positive influence on dry matter production in sunflower [12,68] and safflower [13,15]. The reduction of leaf biomass of both species in both soils under study (Table 1, Table 2) was particularly strong (more than stems) and was more pronounced in loam soil (relative DM production).…”

“…Although the contents of chlorophyll per unit leaf area are often increased under P deficiency [63], the photosynthetic rate per unit area is typically reduced [68], suggesting that both effects (reduction of leaf area and reduction of net photosynthesis per unit of leaf area) may contribute to the final reduction of biomass production. Unlike other reports, sunflower was more sensitive to P deficiency than safflower in terms of relative dry matter accumulation (Table 2) in loam soil under the very low and intermediate P supply and in sandy soil at intermediate P supply [15,70] and the same response was reflected in the relative fresh and dry weights of leaves, stems, and roots (fresh weight). The contribution of the stem in reducing dry matter as affected by sub-optimal external P was less than that of leaves and may be caused by the reduction of stem diameter and the height of the plants [16].…”

“…The decrease in hydraulic conductivity of the root and stomatal conductance of the leaf, result in a severe reduction of leaf expansion under P-deficiency [67]. In addition to the afore mentioned effects on vegetative growth, low-P supply also limits the formation of reproductive organs, results in premature leaf senescence, delayed flower initiation [15], decreased number of flowers [14] and restricted seed formation [15,16], and all contribute to yield reductions under P limited conditions.…”

“…Although, in view of limited P resources [5] and serious environmental and economic consequences [11], a considerate use of P is mandatory to correct nutrient deficiencies [12,13]. P application has been shown to be particularly effective with respect to yield formation in safflower and sunflower [14,15,16], but in organic farming, where application of inorganic P fertilizers is not permitted [17,18], the P availability is not easily increased [19]. Plant species and even cultivars differ in their ability to grow or yield well at suboptimal P supply with remarkable ability to acquire sparingly available soil P, and to utilize internal P efficiently, that could be explored for future use in crops selection [5,12,13,15,16].…”

“…P application has been shown to be particularly effective with respect to yield formation in safflower and sunflower [14,15,16], but in organic farming, where application of inorganic P fertilizers is not permitted [17,18], the P availability is not easily increased [19]. Plant species and even cultivars differ in their ability to grow or yield well at suboptimal P supply with remarkable ability to acquire sparingly available soil P, and to utilize internal P efficiently, that could be explored for future use in crops selection [5,12,13,15,16]. In developing countries, where the proportion of less fertile soils is particularly high, it may be difficult to fulfil the nutritional requirements of high-yielding crops [20].…”