History of the Statistical Design of Agricultural Experiments

Verdooren, L.R.

doi:10.1007/s13253-020-00394-3

Cited by 20 publications

(13 citation statements)

References 87 publications

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“…Multiple comparisons to separate means were carried out with the Student-Newman-Keuls procedure (p < 0.05). The experiment is 20 years older than the introduction of randomized experiments in 1926, which was the start of the modern statistical designing of agricultural experiments [35]. Therefore, no true replications are available, which limits the possibilities of statistical evaluation [36].…”

Section: Discussionmentioning

confidence: 99%

Energy Efficiency of Continuous Rye, Rotational Rye and Barley in Different Fertilization Systems in a Long-Term Field Experiment

et al. 2021

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A goal in sustainable agriculture is to use fossil energy more efficiently in crop production. This 60-year-old experiment on a silt loam chernozem investigated effects of fertilization (unfertilized control, mineral fertilizer (NPK) and farmyard manure (FYM)) and rotation (continuous winter rye (CR), winter rye in rotation (RR), spring barley in rotation (SB) on diesel fuel consumption, total energy input (made of both direct and indirect inputs), crop yield, energy output, net-energy output, energy intensity, energy productivity and energy use efficiency. The input rates of fertilizer, herbicides and seeds were set constant during the experiment. Soil tillage was done with a moldboard plough with subsequent combined seedbed preparation and seeding. The mean calculated total energy input was highest in NPK with 11.28 GJ ha−1 and lowest in the unfertilized control with 5.00 GJ ha−1. Total energy input for FYM was intermediate with 6.30 GJ ha−1. With energetic consideration of NPK nutrients in FYM the total energy input increased to the level of NPK. The share of the fertilizer energy on the total energy input was 49% for NPK. Fertilization with FYM and NPK increased yield and energy output considerably, especially of CR and SB which attained about doubled values. Crop rotation also increased the yield and energy output, especially of unfertilized rye, which attained values increased by about 75%. Fertilization with FYM resulted in the highest energy efficiency as the net-energy output, the energy productivity and the energy use efficiency were higher but the energy intensity was lower compared to unfertilized controls and NPK. When the nutrients in FYM were also energetically considered, the energy efficiency parameters of FYM decreased to the level of the NPK treatment. Crop rotation increased the energy efficiency of winter rye compared to the monoculture.

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Section: Discussionmentioning

confidence: 99%

Energy Efficiency of Continuous Rye, Rotational Rye and Barley in Different Fertilization Systems in a Long-Term Field Experiment

et al. 2021

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“…Ronald Fisher realized that the randomization is needed in order to satisfy the assumption of independent errors, and he introduced the principles of randomization in his book, Statistical Methods for Research Workers [ 27 , 28 ]. The randomization is an important component of experimental design to reduce bias in parameter estimation.…”

Section: Introductionmentioning

confidence: 99%

Applications of statistical experimental designs to improve statistical inference in weed management

Kim

Magana-Ramirez

2021

PLoS ONE

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In a balanced design, researchers allocate the same number of units across all treatment groups. It has been believed as a rule of thumb among some researchers in agriculture. Sometimes, an unbalanced design outperforms a balanced design. Given a specific parameter of interest, researchers can design an experiment by unevenly distributing experimental units to increase statistical information about the parameter of interest. An additional way of improving an experiment is an adaptive design (e.g., spending the total sample size in multiple steps). It is helpful to have some knowledge about the parameter of interest to design an experiment. In the initial phase of an experiment, a researcher may spend a portion of the total sample size to learn about the parameter of interest. In the later phase, the remaining portion of the sample size can be distributed in order to gain more information about the parameter of interest. Though such ideas have existed in statistical literature, they have not been applied broadly in agricultural studies. In this article, we used simulations to demonstrate the superiority of the experimental designs over the balanced designs under three practical situations: comparing two groups, studying a dose-response relationship with right-censored data, and studying a synergetic effect of two treatments. The simulations showed that an objective-specific design provides smaller error in parameter estimation and higher statistical power in hypothesis testing when compared to a balanced design. We also conducted an adaptive experimental design applied to a dose-response study with right-censored data to quantify the effect of ethanol on weed control. Retrospective simulations supported the benefit of this adaptive design as well. All researchers face different practical situations, and appropriate experimental designs will help utilize available resources efficiently.

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“…Blocking may be used to control for such trends and heterogeneity, thereby improving precision compared with complete randomization, and many blocked designs have been proposed for the purpose over the last century (Edmondson, 2005;Verdooren, 2020). The simplest blocked design is the randomized complete block design.…”

Section: Introductionmentioning

confidence: 99%

“…Spatial trends and heterogeneity tend to be particularly pronounced in experiments conducted under various forms of induced or natural biotic and abiotic stress, thus causing substantial error and adversely affecting the precision of treatment comparisons (Braun et al., 1992; Cooper et al., 1997; Hübner et al., 2012; Kumar et al., 2007; Qiao et al., 2000; Singh et al., 2003; Weber et al., 2012). Blocking may be used to control for such trends and heterogeneity, thereby improving precision compared with complete randomization, and many blocked designs have been proposed for the purpose over the last century (Edmondson, 2005; Verdooren, 2020). The simplest blocked design is the randomized complete block design.…”

Section: Introductionmentioning

confidence: 99%

Generating row–column field experimental designs with good neighbour balance and even distribution of treatment replications

Piepho

Williams

Michel

2020

J Agronomy Crop Science

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History of the Statistical Design of Agricultural Experiments

Cited by 20 publications

References 87 publications

Energy Efficiency of Continuous Rye, Rotational Rye and Barley in Different Fertilization Systems in a Long-Term Field Experiment

Energy Efficiency of Continuous Rye, Rotational Rye and Barley in Different Fertilization Systems in a Long-Term Field Experiment

Applications of statistical experimental designs to improve statistical inference in weed management

Generating row–column field experimental designs with good neighbour balance and even distribution of treatment replications

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