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The aim of the present study was to compare the potential seed yield of eight quinoa varieties, to explore their mineral composition of seeds and to identify superior varieties in two locations with different soil properties. Compared with neutral soil conditions, seed yield in the marginal (salinesodic) soil was decreased by 45 %. Under the latter soil conditions seed yield was negatively correlated with crop density, indicating that a considerable yield loss was due to poor and uneven plant density caused by adverse soil properties. Among the varieties, ÔRU-5-PQCIP-DAN-IDA-UNAÕ produced the highest seed yield (>20 dt ha )1 ) when grown under neutral soil conditions. Under marginal conditions, the above-mentioned variety and ÔN 407Õ produced seed yields up to 10 dt ha )1 whereas the rest reached yields of only about 5 dt ha )1 . The majority of the varieties accumulated significantly more protein (20 %) in the seeds under saline-sodic soil conditions (lower yielding environment). The varieties originated from South America were superior in accumulating protein in the seeds at both locations. Mineral contents of calcium (Ca), magnesium (Mg), zinc (Zn) and manganese (Mn) in the seeds were significantly higher in the neutral soil. No differences were found for phosphorous (P), iron (Fe), copper (Cu) and boron (B) between the two locations. The South American varieties were again superior in mineral composition. Adaptation of certain quinoa varieties even under marginal environments seems promising for seed production and/or protein and mineral content in the seeds. Agronomic data are needed in a due course, over a higher number of locations and/or various climatic conditions.

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Lysimeters and neighbouring fields were used from 1998 to 2000 to assess parameters of N use efficiency of three Swiss spring wheat (Triticum aestivum L.) genotypes. An old (Albis), a new (Toronit) and an experimental genotype (L94491) were compared with no and ample (250 kg N ha−1) N fertilizer supply. N fertilization increased biomass, grain yield and grain N concentration of all genotypes in all years and in both testing systems (field, lysimeters) but only a few genotype × N interactions were observed. Generally, Toronit was superior in producing biomass and grain yield and L94491 in accumulating N in the grain resulting in identical N biomass yields. Albis showed the lowest and Toronit the highest fertilizer recovery, irrespective of the method of calculation (15N or difference method). The medium yielding L94491 recovered similar amounts of fertilizer N as Toronit, mainly due to the high N concentration in the biomass. The ranking of the genotypes for the investigated traits was similar in both testing systems and results comparable with those reported in the literature, indicating that the lysimeter facility is suitable for investigations of agronomic traits on soil–plant relationships, where a constant recording of the soil properties is required.

Potassium (K) is a primary macronutrient for overall plant growth, yield potential, product quality and stress resistance of crops. Potato (Solanum tuberosum L.) crops require a high amount of potassium to achieve the ideal yield and quality. Therefore, the determination of optimum K rate and efficient source for potato is necessary because K affects crop physiological processes, dry matter production, cooking, and processing requirements. Through modeling on the pooled data extracted from 62 studies, the highest tuber yields might be obtained at an exchangeable soil K level of 200 mg kg−1 approximately, dependent on soil pH, texture, and organic matter. Through modeling on the data of 48 studies, it also revealed that application of potassium sulfate (K2SO4) and potassium chloride (KCl) at rates of 200 kg ha−1 and potassium nitrate (KNO3) at a rate of 100 kg ha−1 might achieve the ideal yield, implying the importance of K sources in potato production. However, these values (either soil exchangeable K content, or fertilizer rates) might not be applicable in a specific growing environment for a specific potato variety. It seems that there is no discrimination among split, pre-plant or in-season application of K, although pre-plant fertilization might be a trustworthy strategy for economic tuber yield. Owing to the luxury consumption of K by potato crop, a combination of factors, including soil exchangeable K level, petiole K concentration, crop removal amount, soil conditions, management practices, climatic conditions, and potato variety, should be considered in order to make rational K fertilizer recommendations.

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