Abstract
Understanding the complex relationships among soil quality, crop productivity, and management practices would help to develop more sustainable agricultural production systems. In this study, we investigated the combined effects of crop rotations and fertilization treatments on soil quality and crop yield in a long term (about 50 years) field experiment. Crop rotations included continuous corn (Zea mays L.), a 2 year corn-wheat (Triticum aestivum L.) rotation, and a 9 year corn-wheat-corn-wheat-corn-wheat-alfalfa-alfalfa-alfalfa (Medicago sativa L.) rotation. Fertilization treatments included control, mineral fertilization with urea and triple superphosphate, and amendment with cattle manure. Crop rotations and fertilization treatments were combined in a factorial experimental design with two replications for each rotation and six replications for each fertilization treatment. The continuous corn and the corn-wheat rotations had negative effects on the main soil quality indicators considered (carbon (C) and nitrogen (N) pools, microbial biomass and activity). On the contrary, the 9 year rotation had positive effects on soil organic carbon (+24%) and total nitrogen (+23%) but resulted in impoverished available P (−5%). Positive effects on soil microbial biomass (+37% of microbial biomass C and +23% of microbial biomass N) and activity (+19%) were also observed. Soil amendment with manure built up soil organic carbon (+13%), increased nutrient content (+31% of extractable C and +19% of extractable N), including that of available P (+47%), and stimulated microbial growth (+34%) and activity (+8%). As compared to manure, mineral fertilization increased the soil nutrient content to a lesser extent. This study showed that the combined use of rotations, including legume forage crops, and soil amendment with manure may help preserve soil quality and crop productivity in the long term.
Highlights
Crop rotation and manure application have been fundamental components of farming for centuries
The results indicated that the long term use of a complex rotation including alfalfa improved soil C and N pools and soil microbial biomass and activity with positive effects on soil quality and functionality
Soil amendment with manure built up soil organic C stocks and acted as a nutrient reservoir, increasing soil total nitrogen content (TN) and mineral N and effectively avoiding P depletion, with positive effects on corn yield
Summary
Crop rotation and manure application have been fundamental components of farming for centuries. With the increased production of mineral fertilizers during the mid-20th century, extensive crop rotations relying on organic soil amendments were supplanted by intensive monocultures or short rotations. These intensively managed systems brought along soil quality degradation problems and increased production costs [1]. Crop rotations are essential components for the development of sustainable agricultural production systems [6,7]. Crop rotations help to preserve soil quality, improving properties such as soil structure and organic matter (OM) content [2]. Crop rotations provide better weed control, increase crop water and nutrient use efficiency (NUE), and reduce diseases pressure, with positive effects on crop yield [8]
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