Drusilla C. Pearson

Conservation Management and Crop Rotation Effects on Weed Populations in a 12-Year Irrigated Study

Potato, dry bean, and sugar beet production have increased markedly in recent years on irrigated cropland in Alberta, Canada. Concerns exist about declining soil quality and increased soil erosion when these low-residue crops are grown in sequence in short-duration rotations. A 12-yr rotation study was conducted to determine the merits of adopting various conservation practices (reduced tillage, cover crops, composted manure) and longer-duration rotations to develop a more sustainable production system for these row crops. This article reports on weed density and weed seedbank data collected in the study. Weed densities recorded prior to applying postemergence herbicides indicated that conservation compared with conventional management treatments had greater weed densities in 30 to 45% of the cases in 3-, 4-, and 5-yr rotations. In contrast, a 6-yr conservation rotation that included 2 yr of timothy forage resulted in similar or lower weed densities than rotations with conventional management practices. Residual weed densities recorded 4 wk after applying postemergence herbicides were only greater in conservation than conventional rotations in 2 of 12 yr, regardless of rotation length. Weed seedbank densities at the conclusion of the 12-yr study were similar for 3- to 6-yr rotations under either conservation or conventional management. These findings indicate that implementing a suite of conservation practices poses little risk of increased weed populations in the long term. This knowledge will facilitate grower adoption of more sustainable agronomic practices for irrigated row crops in this region. Nomenclature: Dry bean, Phaseolus vulgaris L.; oat, Avena sativa L.; potato, Solanum tuberosum L.; rye, Secale cereale L.; sugar beet, Beta vulgaris L.; timothy, Phleum pratense L.; wheat, Triticum aestivum L. La producción de papa, frijol, y de remolacha azucarera ha incrementado en forma marcada en años recientes en zonas agrícolas con riego en Alberta, Canada. Existe preocupación acerca del deterioro de la calidad del suelo y el aumento de la erosión cuando este tipo de cultivos que dejan pocos residuos son producidos en secuencia en rotaciones de corta duración. Un estudio de rotación de 12 años fue realizado para determinar los méritos de la adopción de varias prácticas de conservación (labranza reducida, cultivos de cobertura, estiércol compostado) y rotaciones de mayor duración para desarrollar un sistema de producción más sostenible para estos cultivos. Este artículo reporta los datos colectados de densidad de malezas y banco de semillas en este estudio. Las densidades de malezas registradas antes de aplicar herbicidas postemergentes indicaron que los tratamientos de conservación al compararse con los de manejo convencional tuvieron mayores densidades de malezas en 30 a 45% de los casos, en rotaciones de 3, 4, y 5 años. En contraste, una rotación de conservación de 6 años que incluyó 2 años del forraje Phleum pratense resultó en densidades de malezas similares o menores a las prácticas de manejo convencional. Las densidades de malezas residuales registradas 4 semanas después de la aplicación de herbicidas postemergentes fueron mayores en rotaciones de conservación que en rotaciones convencionales solamente en 2 de los 12 años, sin importar la duración de la rotación. Las densidades del banco de semillas al momento de la conclusión del estudio de 12 años fueron similares para las rotaciones de 3 y 6 años bajo cualquiera de los manejos de conservación o convencionales. Estos resultados indican que el implementar una variedad de prácticas de conservación representa poco riesgo de aumentos en las poblaciones de malezas en el largo plazo. Este conocimiento facilitará la adopción por parte de los productores de más prácticas agronómicas sostenibles para cultivos con riego en esta región.

Crop rotation effects on Pratylenchus neglectus populations in the root zone of irrigated potatoes in southern Alberta

Abstract Root-lesion nematodes (Pratylenchus spp.) are important pests of potato (Solanum tuberosum L.), particularly in sandy soils and in the presence of Verticillium dahliae. We assessed the effects of crop rotation and soil management practices (reduced tillage, cover crops and composted manure applications) on population densities of P. neglectus on potato in a sandy loam soil in southern Alberta. Crops in rotation included potato (P), dry bean (DB, Phaseolus vulgaris L.), wheat (W, Triticum aestivum L.), sugar beet (SB, Beta vulgaris L.), oats (O, Avena sativa L.) and timothy (T, Phleum pratense L.). The rotations included ‘conventional’ and ‘conservation’ versions of 3-year (DB-W-P) and 4-year (W-SB-DB-P) rotations, as well as 5-year (W-SB-W-DB-P) and 6-year (O/T-T-T-SB-DB-P) rotations. Conservation practices included autumn cover crops and incorporation of compost as a substitute for inorganic fertilizer. Population densities of P. neglectus in the potato phase of each rotation were assessed in autumn of 2006 and 2007, and at the beginning, middle and end of 2008, 2009 and 2010 growing seasons. Pratylenchus neglectus populations were affected by rotation length but not soil management practices; population densities in the 3-year rotations were larger than in most other rotations at most sample dates. Potato yields in the 3-year conventional rotation were consistently lower than in longer rotations. In the 3-year rotation, potato was preceded by wheat, which is known to be a good host for P. neglectus. We speculate that greater population build-up on wheat in the year before potato, rather than rotation length or crop diversity per se, was the cause of the larger population densities in the 3-year rotations than in longer rotations.

Sugar beet response to rotation and conservation management in a 12-year irrigated study in southern Alberta

Abstract: Sugar beet (Beta vulgaris L.) has a long history as an option for irrigated crop rotations in southern Alberta. A 12-yr (2000–2011) study compared conservation (CONS) and conventional (CONV) management for sugar beet in 4- to 6-yr rotations which also included dry bean (Phaseolus vulgaris L.), potato (Solanum tuberosum L.), and soft white spring wheat (Triticum aestivum L.). Oat (Avena sativa L.) and timothy (Phleum pratense L.) were included in the longest 6-yr rotation. Conservation management incorporated reduced tillage, cover crops, feedlot manure compost addition, and solid-seeded dry bean. Compared with a 4-yr CONV rotation (52.2 Mg ha-1), sugar beet root yield (averaged over the second 6 yr of the study, 2006–2011) was significantly higher, by 11%, on 4- and 5-yr CONS rotations (57.7–57.9 Mg ha-1), and by 8% on a 6-yr CONS rotation (56.1 Mg ha-1). Sugar beet impurity parameters were significantly affected by rotation in, at most, 3 of 12 yr. However, averaged over the final 6 yr of the study (2006–2011), a significantly higher K concentration (impurity) was found with CONS (2108 mg kg-1) vs. CONV (1958 mg kg-1) management. Integrating CONS management practices into sugar beet rotations led to significant yield benefits while effects on sugar beet quality were minimal.

Economic Comparison of Conventional and Conservation Management Practices for Irrigated Potato Production in Southern Alberta

Conventional (CONV) potato (Solanum tuberosum L.) production in Alberta has relied on high levels of soil disturbance which may result in long-term degradation of soil resources. A 12-yr (2000–2011) study was conducted to address issues with the CONV system and to evaluate the effects of conservation (CONS) practices on the economics of irrigated potato production. Potato was grown in 3- to 6-yr rotations which included dry bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.), soft wheat (Triticum aestivum L.), oat (Avena sativa L.), and timothy (Phleum pratense L.). CONS included reduced tillage, cover crops, compost addition, and solid-seeded bean. Averaged over 12-yr, potato yields for 4-yr CONV rotations (potato–wheat–beet–bean) were lower than those for CONS systems. However, the decreased costs associated with not using compost in 4-yr CONV offset the losses in yield, thereby resulting in an overall net income higher than that of CONS systems.ResumenLa producción convencional de papa (CONV, Solanum tuberosum L.) en Alberta se ha respaldado en altos niveles de alteraciones del suelo, que pudieran resultar en su degradación a largo plazo. Se condujo un estudio de 12 años (2000–2011) para enfatizar temas con el sistema CONV y para evaluar los efectos de prácticas de conservación (CONS) en aspectos económicos de la producción de papa de riego. Se cultivó la papa en rotaciones de 3 a 6 años, que incluían frijol (Phaseolus vulgaris L.), remolacha (Beta vulgarins L.), trigo suave (Triticum aestivum L.), avena (Avena sativa L.) y el pasto bohordillo o hierba timotea (Phleum pratense L.). CONS incluyó labranza mínima, cultivos de cobertura, agregado de composta y frijol en alta densidad. Promediando sobre 12 años, los rendimientos de la papa en rotaciones CONV por 4 años (papa, trigo, remolacha, frijol) fueron más bajos que los de los sistemas CONS. No obstante, la disminución de costos asociada con no usar composta en 4 años de CONV compensa la pérdida en rendimiento, resultando entonces en un ingreso neto total más alto que el de los sistemas CONS.

Soil changes over 12 yr of conventional vs. conservation management on irrigated rotations in southern Alberta

Abstract: Increased irrigated production of potato (Solanum tuberosum L.), dry bean (Phaseolus vulgaris L.), and sugar beet (Beta vulgaris L.) in southern Alberta in the 1990s prompted a 12 yr (2000–2011) study to evaluate conservation (CONS) management practices for these crops in 3–6 yr rotations. Conservation management included reduced tillage, cover crops, compost, and narrow-row dry bean. After 12 yr, soil organic carbon (SOC) at 0–30 cm depth increased by 0.48 Mg ha-1 yr-1 on a 5 yr CONS rotation, in line with average cumulative compost addition of 154 Mg ha-1. In contrast, SOC stocks on a 3 yr conventional (CONV) rotation, which did not receive compost, declined by 0.25 Mg ha-1 yr-1. Nitrate-N did not accumulate in the soil profile under CONS management, as it was largely influenced by previous crop. In contrast, available P increased with compost addition under CONS management, leading to surface buildup and downward movement in the soil profile. At 0–120 cm depth, the CONS rotations showed 26%–53% higher available P than CONV rotations between 2005 and 2011. Apart from a caveat regarding potential P accrual, the CONS management package in this study was validated as soil building for irrigated cropping systems in southern Alberta.

Energy Use Efficiency of Conventional versus Conservation Management Practices for Irrigated Potato Production in Southern Alberta

A 12-yr. (2000–2011) study was conducted in Alberta, Canada to compare the energy use efficiency (EUE) of conventional (CONV) and conservation (CONS) potato (Solanum tuberosum L.) management practices. Potato was grown in 3- to 6-yr. rotations which included dry bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.), soft wheat (Triticum aestivum L.), oat (Avena sativa L.), and timothy (Phleum pratense L.). CONS included compost application, reduced tillage, cover crops, and solid-seeded bean. Findings suggested that potato in 5-yr. CONS produced the highest EUE compared to the other CONS or CONV rotations. CONS can be used as a means of reducing the reliance on non-renewable energy inputs and improving overall EUE of potato production when less than 21% of the N content of compost applied was counted toward energy input use of potato production. At more than 21%, potato in the 4-yr. CONV became more favorable compared to potato in other rotations.ResumenSe condujo un estudio de 12 años (2000–2011) en Alberta, Canadá, para comparar la eficiencia en el uso de energía (EUE), en prácticas de manejo convencional (CONV) y de conservación (CONS) en papa (Solanum tuberosum L.). Se cultivó la papa en rotaciones de 3 a 6 años, que incluía frijol (Phaseolus vulgaris L.), remolacha azucarera (Beta vulgaris L.), trigo suave (Triticum aestivum L.), avena (Avena sativa L.) y el pasto fleo (Phleum pratense L.). El CONS incluía la aplicación de composta, labranza mínima, cultivos de cobertura y frijol de semilla sólida. Lo que se encontró sugirió que la papa, en un CONS de 5 años, producía la más alta EUE, comparada con las otras rotaciones CONS o CONV. El CONS puede usarse como un medio para reducir el respaldo en la aportación de energía no renovable, y mejorando la EUE en general de la producción de papa cuando se contaba con menos del 21% del contenido de N de la composta aplicada, hacia el uso de la aportación de energía de la producción de papa. A más del 21%, la papa en los 4 años de CONV, se volvía más favorable en comparación a la papa en otras rotaciones.

Soft white spring wheat is largely unresponsive to conservation management in irrigated rotations with dry bean, potato, and sugar beet

Abstract: Historically, soft white spring (SWS) wheat (Triticum aestivum L.) has been a crop choice in southern Alberta’s irrigation districts. A 12-yr (2000–2011) study compared conservation (CONS) and conventional (CONV) management for SWS wheat in 3–5-yr rotations with dry bean (Phaseolus vulgaris L.), potato (Solanum tuberosum L.), and sugar beet (Beta vulgaris L.). Conservation management incorporated reduced tillage, compost, cover crops, and narrow-row dry bean. Wheat was largely unresponsive to CONS management, with only 2 of 13 parameters showing significant positive effects: greater grain Ca (605 vs. 576 μg g-1 on CONV) and S concentrations (1137 vs. 1105 μg g-1 on CONV). Two parameters showed significant negative responses to CONS management: shorter plant height (82.8 vs. 84.8 cm on CONV) and higher take-all [Gaeumannomyces graminis (Sacc.) Arx & Olivier var. tritici Walker] severity (1.34 vs. 1.27 rating on CONV). The remaining nine parameters were unresponsive: plant density, days to maturity, grain yield, grain protein concentration, test weight, kernel hardness, wheat stem sawfly [Cephus cinctus Norton (Hymenoptera: Cephidae)] damage, and grain P and K concentrations. With a backdrop of continued decline in irrigated SWS wheat hectarage, we feel our data is relevant to other wheat classes grown under irrigation in southern Alberta.