Posts Tagged ‘wheat’

Specification effects in zero tillage survey data in South Asia’s rice-wheat systems

Posted by on , in Journal Articles

Published in Field Crops Research 111(1-2): 166-172

Specification effects in zero tillage survey data in South Asia’s rice–wheat systems

Olaf Erenstein

Specification effects in terms of how technology options are contrasted can introduce bias in impact assessment. In a companion paper we evaluated the on-farm impacts of zero tillage (ZT) wheat as a resource-conserving technology in the rice–wheat systems of India’s Haryana State and Pakistan’s Punjab province [Erenstein, O., Farooq, U., Malik, R.K., Sharif, M., 2008. On-farm impacts of zero tillage wheat in South Asia’s rice–wheat systems. Field Crop Res. 105, 240–252]. The underlying field work surveyed plots of full adopters (only ZT plots), partial adopters (ZT and conventional tillage [CT] plots on same farm) and non-adopters (only CT plots). The companion paper assumes that the comparison between the ZT plots of full plus partial adopters and CT plots of partial adopters is the least-biased assessment of ZT’s on-farm impact. Here we revisit this underlying assumption and draw on complementary farm survey findings to illustrate the extent of specification effects in the assessment of on-farm impacts of ZT wheat in the same study areas. The study thereby distinguishes between three contrasts between ZT and CT within the same dataset: (1) plain contrast (all plots of adopters and non-adopters); (2) adopter-only contrast (full and partial adopters only, as used in Erenstein et al. [Erenstein, O., Farooq, U., Malik, R.K., Sharif, M., 2008. On-farm impacts of zero tillage wheat in South Asia’s rice–wheat systems. Field Crop Res. 105, 240–252]); (3) pair-wise contrast (partial adopters only). Proceeding from type 1 to type 3 comparisons the number of observations decrease but this is compensated by an increasing ability to control for variation. The ability of type 3 comparisons to pick up relatively small but significant differences is an important consideration in farm survey impact assessment. However, there is also an increase in partial adoption bias and further follow-up studies are needed to understand the implications of this. The comparisons show that the ZT effects on savings for diesel, tractor time and cost for wheat cultivation are particularly robust. In Haryana ZT’s positive implications for yield and the other financial indicators were also statistically robust, but in Punjab these were sensitive to specification effects. Particularly sensitive to specification effects were the ZT effects on the productivity of applied water in both sites.

Specification effects in zero tillage survey data in South Asia’s rice–wheat systems

Posted by on , in Journal Articles

Published in Field Crops Research 111(1-2): 166-172

Specification effects in zero tillage survey data in South Asia’s rice–wheat systems

Olaf Erenstein

Abstract:  Specification effects in terms of how technology options are contrasted can introduce bias in impact assessment. In a companion paper we evaluated the on-farm impacts of zero tillage (ZT) wheat as a resource-conserving technology in the rice–wheat systems of India’s Haryana State and Pakistan’s Punjab province [Erenstein, O., Farooq, U., Malik, R.K., Sharif, M., 2008. On-farm impacts of zero tillage wheat in South Asia’s rice–wheat systems. Field Crop Res. 105, 240–252]. The underlying field work surveyed plots of full adopters (only ZT plots), partial adopters (ZT and conventional tillage [CT] plots on same farm) and non-adopters (only CT plots). The companion paper assumes that the comparison between the ZT plots of full plus partial adopters and CT plots of partial adopters is the least-biased assessment of ZT’s on-farm impact. Here we revisit this underlying assumption and draw on complementary farm survey findings to illustrate the extent of specification effects in the assessment of on-farm impacts of ZT wheat in the same study areas. The study thereby distinguishes between three contrasts between ZT and CT within the same dataset: (1) plain contrast (all plots of adopters and non-adopters); (2) adopter-only contrast (full and partial adopters only, as used in Erenstein et al. [Erenstein, O., Farooq, U., Malik, R.K., Sharif, M., 2008. On-farm impacts of zero tillage wheat in South Asia’s rice–wheat systems. Field Crop Res. 105, 240–252]); (3) pair-wise contrast (partial adopters only). Proceeding from type 1 to type 3 comparisons the number of observations decrease but this is compensated by an increasing ability to control for variation. The ability of type 3 comparisons to pick up relatively small but significant differences is an important consideration in farm survey impact assessment. However, there is also an increase in partial adoption bias and further follow-up studies are needed to understand the implications of this. The comparisons show that the ZT effects on savings for diesel, tractor time and cost for wheat cultivation are particularly robust. In Haryana ZT’s positive implications for yield and the other financial indicators were also statistically robust, but in Punjab these were sensitive to specification effects. Particularly sensitive to specification effects were the ZT effects on the productivity of applied water in both sites.

New book in the library: Wheat Science and Trade

Posted by Petr Kosina on , in New Acquisitions

wheatWheat: Science and Trade is an up-to-date, comprehensive reference work designed to expand the current body of knowledge on this staple crop, incorporating new information made available by genetic advances, improvements in the understanding of wheat’s biology, and changes in the wheat trade industry. Covering phylogeny and ontogeny, manipulation of the environment and optimal management, genetic improvement, and utilization and commercialization, the book focuses on the most economically significant diseases and impacts.

Wheat: Science and Trade is divided into four major sections covering all aspects of the wheat plant, crop, cultivar and industry.  Section one offers a firm grounding in the development and domestication of wheat with an extensive overview of diseases and pathogens following in Section two. Section three focuses on genetic strategies including QTL detection and marker-assisted selection, genome organization and comparative genomics, and synthetic wheat as an emerging technology.  Section four concludes the text with a discussion of changes in industry trade, quality assessment, and new uses for wheat and modified wheat products.

Written by a global team of expert authors, Wheat: Science and Trade is presented in a user-friendly format making it equally accessible to a wide variety of readers.  Applicable for the academic, research, consulting, and end-user communities, this text is a must have reference on this key staple crop.

Key Features:

  • Provides an up-to-date authoritative reference on a globally consumed and produced crop
  • Focuses on the most economically significant production constraints and impacts
  • Includes interconnecting sections on the wheat plant, crop, cultivar, and industry
  • Includes chapters from a world-wide team of leading experts
  • Provides concise summaries for each chapter and perspectives on emerging research areas

The book includes two chapters co-authored by CIMMYT scientists Julie Nicol and Ivan Ortiz Monasterio.

New CIMMYT publication: Wheat Facts and Futures 2009

Posted by Petr Kosina on , in CIMMYT Publications

Dixon, John ; Braun, Hans-Joachim ; Kosina, Petr ; Crouch, Jonathan (2009). Wheat Facts and Futures 2009. CIMMYT. Mexico.

wwff For nearly half a century, the international wheat breeding system has delivered improved high yielding varieties of wheat that created (along with rice) the Green Revolution and underpinned strong growth in wheat productivity in irrigated and rainfed, developed and underdeveloped, regions. Future priorities for breeding and complementary sciences will still include yield but will also diversify in response to changing market demands and growing environments, particulary in developing countries. It is argued that in the coming decades research on wheat quality characteristics will become increasingly important to plant breeders, whose work will be supported by the development of markers and advanced tools from molecular biology. Breeders will have to contend with increased heat stress and variability stemming from climate change, which is expected to create regional winners, as the northern high latitudes grow warmer and moister, and losers, as the sub-tropics and tropics increasingly suffer from heat stress and drought. Yield response of improved varieties in farmers’ fields depends to a very great degree on sustainable systems management, which also is essential to reverse the ongoing degradation of agricultural resources. Finally, the importance of expanding the systems lens from farmers to policy makers, and of linking farmers, commerce, science, and policy is illustrated for the rice-wheat farming systems of South Asia.

New book in the library: Cereals (Handbook of Plant Breeding)

Posted by Petr Kosina on , in New Acquisitions

cereals1 Cereals (Handbook of Plant Breeding). Marcelo J. Carena

The objective of this volume is to increase the utilization of useful genetic resources and increase awareness of the relative value and impact of plant breeding and biotechnology. That should lead to a more sustainable crop production and ultimately food security.

Table of Contents: Section I Cereal Crop Breeding: Maize Breeding; Rice Breeding ; Spring Wheat Breeding ; Rye Breeding; Grain Sorghum Breeding; Durum Wheat Breeding; Barley; Winter and Specialty Wheat; Triticale: A ‘‘New’’ Crop with Old.   Section II Adding Value to Breeding: Statistical Analyses of Genotype by Environment Data; Breeding for Quality Traits in Cereals: A Revised Outlook on Old and New Tools for Integrated Breeding; Breeding for Silage Quality Traits in Cereals; Participatory Plant Breeding in Cereals.