Crop sequence effects of 10 crops in the northern Great Plains

Abstract

Dynamic cropping systems, which involve a long-term strategy of annual crop sequencing, require detailed information on management components known to influence crop performance. Considering that proper sequencing of crops is an important component for successful dynamic cropping systems, a research project was undertaken to determine the advantages and/or disadvantages of previous crop and crop residues for numerous crop sequences. A multi-disciplinary team of scientists evaluated crop sequence effects of 10 crops (barley, canola, crambe, dry bean, dry pea, flax, safflower, soybean, spring wheat, and sunflower) on seed yield, soil coverage by residue, soil water use, surface soil properties, and plant diseases in central North Dakota. Two years were required to establish a crop by crop residue matrix (crop matrix). During the second year (site 1, 1999; site 2, 2000) 10 crops were evaluated with a crop matrix. During the third and fourth year spring wheat (site 1, 2000; site 2, 2001) and sunflower (site 1, 2001; site 2, 2002), respectively, were seeded over the crop matrix. The seed yield of four crops (crambe, flax, safflower, and soybean) of the 10 crops evaluated in the crop matrix was influenced by the preceding crop at site 1 in 1999 an above average moisture year. The seed yield of eight crops (canola, crambe, dry bean, flax, safflower, soybean, spring wheat, and barley) was influenced by the preceding crop at site 2 in 2000 a more average precipitation year. Some of the lowest seed yields were obtained when a crop was seeded on its own residue. A synthesis of seed yield data from a given year provided overall values for positive and negative effects of crops and crop residue on subsequent crops. In general, the three legume crops had positive effects in contrast to non-leguminous crops, which usually had negative effects. However, sunflower was an exception among the non-leguminous crops; at site 2 in 2000, sunflower was positive for subsequent crops compared with canola or crambe, which had negative effects. Crop sequences composed of small cereal grains had the highest soil coverage by residue while sequences of two dicotyledonous species had considerably lower coverage. Soil water use among crops varied, ranging from sunflower with the numerically highest soil water use to dry pea with the least. Significant changes in surface soil properties due to crops were generally not detected in this short-term project. Given the variation in Sclerotinia disease incidence for canola, crambe, safflower, and sunflower within the crop matrix, it was difficult to detect significant differences based on the previous crop. Differences were evident two years later when the highest incidence of Sclerotinia basal stalk rot for sunflower was detected in plots where crambe was grown two years earlier. During the third year, when spring wheat was seeded over a crop matrix, spring wheat yields increased following 23 and 19 crop sequence treatments out of a possible 100 at site 1 and site 2, respectively, compared to the continuous wheat treatment. All crop sequence treatments that yielded better than the continuous wheat treatment were comprised of mostly non-cereal crops, demonstrating the positive impact of crop diversity on cereal crop production. The severity of leaf spot diseases on spring wheat were affected by crop sequence and fungal spore production was greatest on the continuous wheat treatment. Even though decreases in leaf spot disease severity and modest yield increases were obtained with some crop sequence treatments, significant yield increases due to reduced leaf spot disease severity were not obtained under our conditions.

Introduction

The northern Great Plains of North America is recognized throughout the world for its fertile soils, which contribute to the production of large quantities of cereal grain, oilseed, and pulse crops. This area, which includes most of Montana, North Dakota, South Dakota, and parts of Wyoming and Nebraska in the United States as well as arable regions of Manitoba, Saskatchewan, Alberta, and British Columbia in Canada, contains approximately 52 Mha of cropland and contributes over $20billion in annual agricultural output (Padbury et al., 2002, Statistics Canada, 2003, US Census Bureau, 2002). Despite this impressive level of production, there are concerns about the sustainability of cropping systems within the region. High climatic variability within the northern Great Plains leads to economic instability of crop production practices (Peterson, 1996). This instability is exacerbated by historical and current trends that include a lack of crop diversity (Brummer, 1998, Peterson et al., 1996), declines in soil organic matter (Campbell et al., 1996, Lyon et al., 1997), and improper management of crop nutrients (Westfall et al., 1996).

Diversification, opportunism, risk avoidance, and flexibility are four principles considered essential to create a more sustainable agriculture in highly dynamic ecoregions such as the northern Great Plains (Behnke et al., 1993, Dhuyvetter et al., 1996, Sandford, 1982). Development and utilization of more diverse cropping systems is closely aligned with these principles. Diverse cropping systems have been proposed to reverse many of the negative socio-economic and environmental impacts of predominant crop production practices in the region (Zentner et al., 2001). For such a reversal to occur, however, information on the agronomic potential, environmental impact, and economics of alternative crops is needed. Obtaining such information is complicated by the fact that individual crops interact differently with numerous management components, such as tillage methods, crop sequencing, cultivar selection, nutrient management, and weed and disease control. Understanding how individual crops and management components interact is essential in the development of practical, efficient, and cost-effective cropping systems capable of stabilizing crop production while minimizing deleterious effects on the environment (Hanson et al., 2003).

Tanaka et al. (2002) developed the concept of dynamic cropping systems to facilitate the determination of causal relationships between crop performance and specific management components. As defined, dynamic cropping systems refer to a long-term strategy of annual crop sequencing that optimizes crop and soil use options and the attainment of production, economic, and resource conservation goals by using sound ecological management principles (Tanaka et al., 2002). Optimizing cropping options to meet these goals requires detailed information on multiple management components known to influence crop performance. This information should provide clearer recommendations for proper crop sequencing, which has long been viewed as crucial for cropping system success (Leighty, 1938, Pierce and Rice, 1988).

The objective of this study was to determine the advantages and/or disadvantages of previous crop and crop residues for numerous crop sequences in the northern Great Plains. Specifically, we sought to evaluate the effects of crop sequencing on crop performance, soil coverage by residue, soil water use, surface soil properties, and plant diseases in a crop matrix.