4R Management of Phosphorus Fertilizer in the Northern Great Plains.

Phosphorus (P) fertilizer has played a vital role in increasing the productivity of crop production in the northern Great Plains for approximately 100 years. Throughout this period, agricultural production practices have changed dramatically, while our knowledge of P behavior and beneficial management practices has improved. Some of the more recent and substantial changes in farming practices on the northern Great Plains include widespread adoption of reduced tillage systems, introduction of new crops and high-yielding cultivars, intensification and extension of crop rotations, development of new fertilizer products, increased appreciation of the role of microbial interactions in P dynamics, and growing concern for the effects of P on water quality. As cropping systems, technology, and societal demands evolve over time, nutrient management practices must also evolve to address concerns and take advantage of emerging opportunities. Classic principles and new P fertilizer technologies and management practices must be integrated into packages of 4R practices that optimize crop yield and agronomic efficiency while minimizing negative environmental impact and conserving P resources. Although a wide range of products and practices can be combined for this approach, placing ammonium phosphate fertilizer in a band, in or near the seed-row, at the time of seeding and at a rate that matches P removal by the crop generally provides the greatest P efficiency, long-term sustainability, and environmental protection for small grain, oilseed, and pulse crop production in the northern Great Plains.

Effects of seeding rate, nitrogen rate and cultivar on barley malt quality.

BACKGROUND: Crop management tools have been shown to affect barley kernel size and grain protein content, but the direct effect on malt quality is not well understood. The present study investigated the effect of seeding rate, nitrogen fertilisation and cultivar on malt quality. RESULTS: Higher seeding rates produced barley with less grain protein and smaller, more uniformly sized kernels. The small, uniformly sized kernels modified more completely, leading to malt with higher extract and lower wort ß-glucan than malt from low-seeding-rate barley. Increasing rates of nitrogen fertilisation caused grain protein levels to increase, which limited endosperm modification and reduced malt extract levels. AC Metcalfe showed better modification and higher malt extract than CDC Copeland, but CDC Copeland had better protein modification at higher fertilisation rates, which resulted in less reduction of malt extract as nitrogen rate increased. CONCLUSION: Higher seeding rates reduced kernel size and grain protein levels without compromising malt extract owing to better endosperm modification of the more uniformly sized kernels. Negative effects of higher nitrogen rates on malt quality can be reduced through development of cultivars with improved ability to modify protein during malting.

Mycorrhizal colonization and grain Cd concentration of field-grown durum wheat in response to tillage, preceding crop and phosphorus fertilization.

BACKGROUND: A 3-year field trial was conducted to investigate the effect of agricultural management practices including tillage, preceding crop and phosphate fertilization on root colonization by arbuscular mycorrhizal (AM) fungi and grain cadmium (Cd) concentration of durum wheat (Triticum turgidum L.). The relationship between grain Cd and soil and plant variables was explored to determine the primary factors affecting grain Cd concentration. RESULTS: Mycorrhizal colonization of the roots was reduced by conventional tillage or when the preceding crop was canola (Brassica napus L.), compared to minimum tillage or when the preceding crop was flax (Linum usitatissimum L.). In contrast, grain Cd was not consistently affected by any treatment. Grain Cd was generally below the maximum permissible concentration (MPC) of 100 microg Cd kg(-1) proposed by WHO. Grain Cd varied substantially from year to year, and could be predicted with 70% of variance accounted for by using the model: grain Cd concentration = - 321.9 + 44.5x ln(grain yield) + 0.26x soil DTPA-Cd + 182.5x soil electrical conductivity (EC)- 0.98x grain Zn concentration. CONCLUSIONS: These common agricultural management practices had no effect on grain Cd concentration in durum wheat though they impacted mycorrhizal colonization of roots. Grain yield and to a lesser extent soil conditions of EC and DTPA-Cd and grain Zn influenced grain Cd, whereas mycorrhizal colonization levels did not.

Cadmium concentration in durum wheat grain (Triticum turgidum) as influenced by nitrogen rate, seeding date and soil type.

BACKGROUND: Cadmium (Cd) is a trace element that has been associated with various human health problems. Cd enters plants, either by direct absorption through leaves or by uptake from soils, allowing Cd into the food chain. Nitrogen (N) fertilizer management is important in optimizing crop yield and protein content of durum wheat, but may influence Cd availability and hence Cd concentration in crops, with the effects being strongly influenced by environmental conditions and crop cultivar. RESULTS: In field studies, Cd and protein concentration in durum wheat grain differed between cultivars and were strongly affected by N application, with only minor effects of N occurring on concentration and uptake of P and Zn. Protein content increased significantly with N application in five of six site-years, with the response being generally independent of cultivar and seeding data. Cd concentration also increased with N application in five of six seeding dates, with the response being greater in AC Melita than Arcola in three of the six site-years. There were large differences in Cd concentration from year to year and with seeding date, indicating a strong environmental influence. CONCLUSIONS: This study shows that different cultivars accumulate different levels of Cd in the grain and that seeding date and nitrogen fertilizer management can influence grain Cd concentration, with the magnitude of effects varying with environmental factors. In the future we may be able to manipulate management practices to optimize protein concentration and minimize Cd concentration in durum wheat, which could help to address the health and safety concerns of consumers.