Burton L. Johnson

Effect of field limestone applications on cadmium content of sunflower (Helianthus annuus L.) leaves and kernels

Nonoilseed sunflower (Helianthus annuus L.) is naturally higher in cadmium (Cd) than many other grain crops. Because raising soil pH usually depresses Cd uptake by most species, a study was designed to determine if application of agricultural limestone to neutralize soil acidity would decrease Cd uptake by sunflower plants grown on different soils in the production area of North Dakota. The field experiments were conducted at 3 locations in 1991 and 2 locations in 1992. At each site, limestone was applied to bring soil pH to 6.5–7.0, or an additional 45 Mg ha-1 more limestone was applied, and these two treatments were compared to no-lime control. Commercial nonoilseed hybrid 954 was planted in these experiments. The rapid short-term lime-soil reaction occurred in first 12 weeks following limestone application. Mean kernel Cd concentration for each treatment varied from 0.35 to 1.45 mg kg-1 DW in the first year of the experiments, and from 0.37 to 1.23 mg kg-1 DW in the experiments of 1992 across all locations. Large variations in kernel Cd levels between locations were obtained. There were no significant differences among control and limestone treatments for kernel Cd, seedling leaf Cd and diagnostic leaf Cd within each location, respectively. In regression analysis, we found that kernel Cd level correlated with diagnostic leaf Cd concentration in each treatment, but poor correlations were obtained among other variables. These results indicated that limestone application did not reduce Cd uptake and transfer to kernels of sunflower, in contrast with most species studied.

Zinc Fertilization Effects on Seed Cadmium Accumulation in Oilseed and Grain Crops Grown on North Dakota Soils

The Cd concentration in the seed of crops depends on various soil factors including parent material, texture, pH, soil redox, and salinity. Cadmium accumulation also varies among crop species and cultivars within a species. Cadmium and Zn may have either an antagonistic or a synergistic effect on plant uptake that can be influenced by the soil Cd and Zn concentrations. The objective was to determine the effect of Zn fertilizer additions on the seed Cd of nine crops commonly grown in North Dakota, USA. Studies were conducted at five North Dakota locations representing different soil series during 1994 and 1995. In Experiment 1, nine crops common in North Dakota were grown with and without the addition of 25 kg ha-1 Zn fertilizer. Among crops evaluated, the greatest seed Cd accumulation occurred in flax ( Linum usitatissimum L.) followed by sunflower ( Helianthus annuus L.), soybean ( Glycine max [L.] Merr.), and durum wheat ( Triticum turgidum L. var. durum). In Experiment 2, two durum wheats and one flax cultivar were grown under three Zn treatments of 0, 5, and 25 kg ha-1. In Experiment again flax had the higher seed Cd level compared with the two durum varieties. Based on the results from both studies, addition of Zn fertilizer did not consistently reduce seed Cd content, and even when statistically significant, the level of reduction was small and not likely to impact marketability of Cd accumulating crops such as flax, sunflower, soybean, and durum.

Borage (Borago officinalis L.) Response to N, P, K, and S Fertilization in South Central Chile

Borage (Borago officinalis L.) is an oilseed with a high gamma-linolenic acid (GLA) content in its seed. The objective of this study was to determine the response of borage seed yield, oil content, and fatty acid composition to N, P, K, and S fertilizer treatments. Three experiments were conducted in Osorno (40o22’ S, 73o04’ W; 72 m.a.s.l.), Chile. The first experiment was conducted during the 2005-2006 growing season, with four N rates (0, 100, 200, and 300 kg N ha -1 ), three P rates (0, 60, and 120 kg P2O5 ha -1 ) and two K rates (0 and 150 kg K2O ha -1 ). The second experiment was conducted in 2006-2007 and evaluated only the effect of four N rates (0, 50, 100 and 150 kg N ha -1 ) was evaluated because there was no response to P and K in the first experiment. The third experiment was conducted in the 2005-2006 and 2006-2007 and evaluated only two rates of S, 0 and 40 kg S ha -1 were evaluated. Seed yield was not affected by N, P, K, or their interactions in any of the experiments. As N rates increased GLA content increased. Mean seed yield increased to 98 kg ha -1 when appliying of 40 kg S ha -1 . Results indicate that borage has a higher response to S applications than N. Further research is needed to determine the interactions between N and S applications, given that the experiments were conducted on soils with high levels of P and K levels.

Adaptation and Genotype x Environment Interaction of Flaxseed (Linum usitatissimum L.) Genotypes in South Central Chile

Flaxseed (Linum usitatissimum L.) is imported into Chile mostly for bread making and feed. Identification of genotypes best adapted for seed production in South Central Chile would facilitate producer’s decision. The objective of this study was to determine the adaptation and genotype x environment interaction of 16 flaxseed genotypes (including 10 from North American and six from Argentine sources) grown at 11 environments (defined as location-year) in Chile from 2003 to 2007. Genotype seed yield was above 5700 kg ha -1 for some environments indicating a high yield potential. According to the AMMI (Additive Main Effects and Multiplicative Interaction) and SREG (Sites regression) models the 11 environments were classified into four groups by the AMMI and three groups by the SREG models. Genotypes were classified into five groups by the SREG model with four of the groups as single genotypes. Overall mean seed yield was similar for all genotypes; however the genotype Nekoma was the most stable and higher yielding genotype across environments. The environment with the highest yield potential was Chillan 2003-2004, but this location had low yield stability across years. The environments with greatest seed yield potential, Chillan 2003-2004 and Los Angeles 2004-2005, had irrigation during flowering and seed filling. Seed oil content fluctuated between 420 and 530 g kg -1 . The climatic differences among environments did not influence oil composition as expected from previous research. Flaxseed appears adapted to South Central Chile with differences observed among genotypes for biomass and seed yield, harvest index, test weight, oil content, and composition.

Genotype × Environment Interaction in Canola (Brassica napus L.) Seed Yield in Chile

Genotype x environment (G × E) interaction in canola ( Brassica napus L.) cultivar seed yield is unknown in Chile. The interaction was performed with the SREG (Sites Regression) model. Two experiments were conducted in five and thirteen environments in the 2008-2009 season in Central South Chile. The experimental design was a randomized complete block (RCBD) in each environment with four replicates and 26 open-pollinated or hybrid canola genotypes in Experiment 1, and RCBD with three replicates and 17 genotypes in Experiment 2. ANOVA was used to determine the significance of the G × E interaction. Biplots were used to graphically interpret and determine the best cultivar in each environment and the corresponding mega-environments. The G × E interaction was significant for seed yield in many locations in one cropping season. Most of the analyzed seed yield variation was due to environment and G × E effects. Principal components (PC1 and PC2) of the Sites Regression (SREG) model, with five and eight environments, accumulated 74.5% and 61.1% of the total variation, respectively. Two mega-environments were formed; the first being the Chillan environment while the second included the remaining environments. Six of the evaluated cultivars, all hybrids except ‘Goya’, were superior. The mean vs. stability analysis indicated that the Monalisa hybrid had the highest yield and was the most stable cultivar across all environments. Although the information is for only 1 yr, results could change with data from several years of experimentation. Hence, the study was carried out in many locations in order to provide validity to the results.