Cropping systems that include forage legumes and small grains in addition to corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] can achieve similar or higher crop productivity and economic return than simpler corn–soybean rotations. We hypothesized that this rotation effect occurs regardless of the crop genotype planted and the herbicide and cultivation regime selected for weed management. To test this hypothesis, we conducted a 3-year experiment that compared three cropping systems: a conventional 2-year corn–soybean rotation, a 3-year corn–soybean–oat (Avena sativa L.)/red clover (Trifolium pretense L.) rotation, and a 4-year corn–soybean–oat/alfalfa–alfalfa (Medicago sativa L.) rotation. Within each cropping system, two contrasting sets of management strategies were used: (i) genetically engineered corn with resistance to insect pests (Ostrinia nubilalis Hübner and Diabrotica spp.) plus the broadcast application of pre-emergence herbicides, followed in the rotation by a genetically engineered soybean variety with resistance to the herbicide glyphosate plus the post-emergence broadcast application of glyphosate; and (ii) non-genetically engineered corn plus the banded application of post-emergence herbicides, followed in the rotation by a non-genetically engineered soybean and banded application of several post-emergence herbicides. The two management strategies were identified as ‘GE’ and ‘non-GE.’ Corn yield was higher in the 3-year (12.51Mgha−1) and 4-year (12.79Mgha−1) rotations than in the conventional 2-year (12.16Mgha−1) rotation, and was also 2% higher with the GE strategy than with the non-GE strategy. Soybean yield was similar among rotation systems in 2008, but higher in the 3- and 4-year systems than the 2-year rotation in 2009 and 2010. Soybean yield was similar between management strategies in 2008, but higher in the GE strategy in 2009, and similar between strategies in the 3- and 4-year rotations in 2010. Increases in rotation length were accompanied by 88–91% reductions in synthetic N fertilizer application, and the use of the non-GE rather than the GE strategy was accompanied by a 93% reduction in herbicide active ingredients applied. Averaged over the period of 2008–2010, net returns to land and labor were highest for the 3-year rotation managed with either the GE ($928ha−1yr−1) or non-GE ($936ha−1yr−1) strategies, least in the 2-year rotation managed with the non-GE strategy ($738ha−1yr−1), and intermediate in the other rotation×management combinations. Our results indicate that more diverse crop rotation systems can be as profitable as conventional corn–soybean systems and can provide farmers with greater flexibility in crop management options.
Diversified cropping systems can have high soil microbial biomass and thus strong potential to reduce the weed seedbank through seed decay. This study, conducted in Iowa, USA, evaluated the hypothesis that weed seed decay is higher in a diversified 4-year maize-soyabean-oat/lucerne-lucerne cropping system than in a conventional 2-year maize-soyabean rotation. Mesh bags filled with either Setaria faberi or Abutilon theophrasti seeds and soil were buried at two depths in the maize phase of the two cropping systems and sampled over a 3-year period. Setaria faberi seed decay was consistently greater at 2 cm than at 20 cm burial depth and was higher in the more diverse rotation than in the conventional rotation in 1 year. Abutilon theophrasti seeds decayed very little in comparison with seeds of S. faberi. Separate laboratory and field experiments confirmed differences in germination and seed decay among the seed lots evaluated each year. Fusarium, Pythium, Alternaria, Cladosporium and Trichoderma were the most abundant genera colonising seeds of both species. A glasshouse experiment determined a relationship between Pythium ultimum and S. faberi seed decay. Possible differences in seed susceptibility to decay indicate the need to evaluate weed seedbank dynamics in different cropping systems when evaluating overall population dynamics and formulating weed management strategies.
© 2017 Agronomía Mesoamericana es desarrollada en la Universidad de Costa Rica y se encuentra licenciada con Creative Commons Reconocimiento-NoComercial-SinObraDerivada 3.0 Costa Rica. Para más información escríbanos a pccmca@ucr.ac.cr ResumenEl objetivo de este trabajo fue realizar un diagnóstico sobre el conocimiento que tienen agricultores de papaya, palma aceitera y banano de Costa Rica, sobre coberturas vivas y la disposición a implementarlas. Se construyó un instrumento de evaluación que consistió de veintiocho preguntas para contestar falso o verdadero, con las cuales se creó un indicador de conocimiento. Además, se incluyeron siete preguntas con las respuestas en una escala de cinco puntos, para explorar la disposición del productor a implementar coberturas vivas en su finca. Este instrumento se aplicó en el año 2014 a 36 productores de papaya, 30 de palma aceitera y 57 bananeros. El análisis de ítemes, para determinar confiabilidad, produjo valores alfa de Cronbach superiores al 90%. Se realizó también un análisis de factores para asegurar que el instrumento medía un único rasgo: conocimiento sobre coberturas vivas. El comportamiento de los puntajes globales de conocimiento varió de manera considerable de un grupo de productores a otro. El promedio más alto y con menor variabilidad se obtuvo en los instrumentos aplicados a productores de banano, mientras que el promedio menor y con mayor variabilidad se determinó de los productores de papaya. Las respuestas a cada una de las preguntas variaron considerablemente de un grupo de productores a otro. La mayoría de los productores de los tres cultivos estuvo dispuesto a utilizar coberturas vivas y a recibir capacitación.Palabras clave: cultivos de cobertura, leguminosas, cobertura verde. AbstractThe objective of this study was to assess the knowledge on cover crops and native vegetation mulches and the willingness to implement them by papaya, oil palm, and banana producers in Costa Rica. An evaluation instrument with twenty eight questions to be answered as true or false was developed, and it was used to yield a knowledge
En Costa Rica, al igual que en varios otros países cafetaleros de la región, la mayoría de las plantaciones de café se encuentran en zonas de ladera, con pendientes de hasta un 60 % y en algunos casos de gran longitud. Lo anterior provoca que el agua de lluvia, por medio del salpique y la escorrentía, erosione estos suelos
Table of Contents Chapter 1. General Introduction Dissertation organization References Chapter 2. Comparison of crop management strategies involving crop genotype and weed management practices in conventional and low-externalinput cropping systems
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