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Integrated crop-livestock systems (ICLS) represent a potential means to sustainably intensify agriculture. Developing ICLS that concurrently achieve production and environmental goals is contingent upon efficiently managing plant nutrients in time and space. In this study, we sought to quantify residue management and field-zone effects on soil NO 3 -N, available P, and soil pH over a 12 year period for an ICLS experiment near Mandan, ND USA. From 1999 to 2011, soil NO 3 -N and available P were measured in three residue management treatments (grazed, mechanically harvested, and no residue removal) every third year across a 122 cm soil depth, while soil pH was measured prior to deploying ICLS treatments in 1999 and again in 2011. Residue management did not affect soil NO 3 -N or available P at any depth for any year (P > 0.1), implying no accumulation of available N and P under grazing compared to cropping. Similarly, no differences in available N and P were observed across grazed sampling zones. Soil nutrients, however, increased or fluctuated greatly over the 12 year period, suggesting a need for adaptive nutrient management. Soils became more acidic between 1999 and 2011, with the greatest decreases in soil pH at 0–8 cm under grazing (0.74 pH unit decline; P = 0.0581) and mechanical harvest (0.86 pH unit decline; P = 0.0138). Management interventions targeting nutrient conservation may serve to mitigate N and P loss and soil acidification in ICLS. [ABSTRACT FROM AUTHOR]

The extreme climate of the northern Great Plains of North America requires cropping systems to possess a resilient soil resource in order to be sustainable. This paper summarizes the interactive effects of tillage, crop sequence, and cropping intensity on soil quality indicators for two long-term cropping system experiments in the northern Great Plains. The experiments, located in central North Dakota, were established in 1984 and 1993 on a Wilton silt loam (FAO: Calcic Siltic Chernozem; USDA: fine-silty, mixed, superactive frigid Pachic Haplustoll). Soil physical, chemical, and biological properties considered as indicators of soil quality were evaluated in spring 2001 in both experiments at depths of 0–7.5, 7.5–15, and 15–30 cm. Management effects on soil properties were largely limited to the surface 7.5 cm in both experiments. For the experiment established in 1984, differences in soil condition between a continuous crop, no-till system and a crop–fallow, conventional tillage system were substantial. Within the surface 7.5 cm, the continuous crop, no-till system possessed significantly more soil organic C (by 7.28 Mg ha-1), particulate organic matter C (POM-C) (by 4.98 Mg ha-1), potentially mineralizable N (PMN) (by 32.4 kg ha-1), and microbial biomass C (by 586 kg ha-1), as well as greater aggregate stability (by 33.4%) and faster infiltration rates (by 55.6 cm h-1) relative to the crop–fallow, conventional tillage system. Thus, soil from the continuous crop, no-till system was improved with respect to its ability to provide a source for plant nutrients, withstand erosion, and facilitate water transfer. Soil properties were affected less by management practices in the experiment established in 1993, although organic matter related properties tended to be greater under continuous cropping or minimum tillage than crop sequences with fallow or no-till. In particular, PMN and microbial biomass C were greatest in continuous spring wheat (with residue removed) (22.5 kg ha-1 for PMN; 792 kg ha-1 for microbial biomass C) as compared with sequences with fallow (SW–S–F and SW–F) (Average=15.9 kg ha-1 for PMN; 577 kg ha-1 for microbial biomass C). Results from both experiments confirm that farmers in the northern Great Plains of North America can improve soil quality and agricultural sustainability by adopting production systems that employ intensive cropping practices with reduced tillage management. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]