DOI: 10.5061/dryad.n73v54m
title: Data from: Plant population and maize grain yield: a global systematic review of rainfed trials

description: Maize (Zea mays L.) productivity has increased globally as a result of
 improved genetics and agronomic practices. Plant population and row
 spacing are two key agronomic factors known to have a strong influence on
 maize grain yield. A systematic review was conducted to investigate the
 effects of plant population on maize grain yield, differentiating between
 rainfall regions, N input, and soil tillage system (conventional tillage
 [CT] and no-tillage [NT]). Data were extracted from 64 peer-reviewed
 articles reporting on rainfed field trials, representing 13 countries and
 127 trial locations. In arid environments, maize grain yield was low (mean
 maize grain yield = 2448 kg ha−1) across all plant populations with no
 clear response to plant population. Variation in maize grain yield was
 high in semiarid environments where the polynomial regression (p &lt;
 0.001, n = 951) had a maximum point at ∼140,000 plants ha−1, which
 reflected a maize grain yield of 9000 kg ha−1. In subhumid environments,
 maize grain yield had a positive response to plant population (p &lt;
 0.001). Maize grain yield increased for both CT and NT systems as plant
 population increased. In high-N-input (r2 = 0.19, p &lt; 0.001, n = 2
 018) production systems, the response of plant population to applied N was
 weaker than in medium-N-input (r2 = 0.49, p &lt; 0.001, n = 680)
 systems. There exists a need for more metadata to be analyzed to provide
 improved recommendations for optimizing plant populations across different
 climatic conditions and rainfed maize production systems. Overall, the
 importance of optimizing plant population to local environmental
 conditions and farming systems is illustrated.
description: Maize plant population
 and row spacing dataTo collate peer-reviewed
 articles, a literature search was conducted using the Institute for
 Scientific Information Web of Science Database
 (http://apps.webofknowledge.com). The “Web of Science Core Collection”
 option was used. No timeframe limitation was set and the last online
 search was conducted on 5 September 2017. The keywords used included
 combinations of “corn yield”, “maize yield”, “plant population”, “planting
 density”, “sowing rate”, “planting rate”, “corn population”, and “maize
 population”. When articles were unavailable online or from local
 libraries, a request was made directly to author(s) of the particular
 article to provide a reprint. Articles were read in full text and examined
 on the basis of the following eligibility criteria: (i) plant population
 was evaluated as a treatment to investigate the effects thereof on maize
 grain yield, (ii) data reported were generated by field experiments with
 sound statistical designs, and (iii) field trials received no irrigation
 prior to planting or during the growing season. Any article that was not
 in English or did not meet the abovementioned eligibility criteria was
 excluded. Field trial data generated for modelling purposes were included.
 To overcome publication bias challenges, studies selected for analysis
 were not geographically limited. This ensured the inclusion of field trial
 data from various climatic conditions, combined with different agronomic
 management systems.Appendix C. Supplementary
 data.xlsx