Density and relative frequency effects on competitive interactions and resource use in pea–barley intercrops |
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| Institution: | 1. Biosystems Department, Risø National Laboratory, Frederiksborgvej 399, DK-4000 Roskilde, Denmark;2. Plant Breeding and Crop Science, Department of Agricultural Sciences, The Royal Veterinary and Agricultural University, Højbakkegård Alle 10, DK-2630 Taastrup, Denmark;1. Key Laboratory of Plant and Soil Interactions, Ministry of Education, Center for Resources, Environment and Food Security, China Agricultural University, Beijing 100193, China;2. Institute of Soils, Fertilizers and Water-Saving Agriculture, Gansu Academy of Agricultural Sciences, Lanzhou 730070, China;3. Crop Research Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China;4. Agri-Environment Branch, Agri-Food and Biosciences Institute, Newforge Lane, Belfast BT9 5PX, UK;1. Bureau of Academic Divisions, Chinese Academy of Sciences, Beijing 100190, China;1. College of Resources and Environmental Science, National Academy of Agriculture Green Development, China Agricultural University, Beijing, 100193, China;2. Wageningen University, Soil Biology Group, P.O. Box 47, 6700 AA, Wageningen, the Netherlands;3. Wageningen University, Centre for Crop Systems Analysis, P.O. Box 430, 6700 AK, Wageningen, the Netherlands;4. Inner Mongolia Key Lab. of Soil Quality and Nutrient Resources, Key Lab. of Grassland Resource (IMAU), Ministry of Education, College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot, 010018, China;5. Institute of Soils and Fertilizers, Gansu Academy of Agricultural Sciences, Lanzhou, 730070, China;1. Institute of Soil and Water Conservation, University of Chinese Academy of Sciences and Ministry of Water Resources, Yangling 712100, China;2. Institute of Water Saving Agriculture in Arid Regions of China, Northwest A&F University, Yangling 712100, China;3. College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, China;1. China Agricultural University, College of Agricultural Resources and Environmental Sciences, Beijing 100193, China;2. Wageningen University, Centre for Crop Systems Analysis (CSA), Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands;3. China Institute of Water Resources and Hydropower Research, Beijing, 100038, China;4. Institute of Cotton Research of the Chinese Academy of Agricultural Sciences, State Key Laboratory of Cotton Biology, Anyang, Henan, 455004, China;5. Beijing Meteorological Bureau, Beijing, 100089, China;1. INRA, UMR211 Agronomie, F-78850 Thiverval-Grignon, France;2. AgroParisTech, UMR211 Agronomie, F-78850 Thiverval-Grignon, France |
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| Abstract: | Intercropping advantages may be influenced by both plant density and relative frequency of the intercrop components. In a field study barley (Hordeum vulgare L.) and pea (Pisum sativum L.) were sole cropped and intercropped at three densities and with two relative frequencies when intercropped.Earlier seedling emergence gave barley an initial growth advantage, assessed using the relative efficiency index (REIc), whereas pea was in general more growth efficient once the initial growth phase had been passed. This reversal in relative growth efficiency along with the observation that early barley dominance did not appear to suppress pea growth indicates that differences in phenology played a role in shaping the prevailing dynamics. Whereas increases in plant density had a positive effect on the growth of pea, the growth of intercropped barley was severely limited by increases in density at the end of the growing period and more so in the pea dominated intercrop. At the final harvest land equivalent ratios (LER) of 0.9–1.2 express resource complementarity in almost all studied intercrops, complementarity that was not directly affected by changes in plant density or relative frequency.Intercropped pea did not increase its reliance on atmospheric nitrogen fixation compared to the pea sole crop. With respect to soil nitrogen uptake there were no effect of plant density but a strong effect of the relative frequency of pea in the intercrop, the greater the proportion the lower the uptake.Changes in the competitive strength of the pea and barley crop over the growing season had a marked effect on the proportion of pea in the final grain yields of the intercrops. At low and recommended density the proportions of pea and barley in the final grain yield was not markedly different from the expected proportions sown; however, at high density the suppression of barley strongly increased the proportion of pea in the final grain yield.Weed infestation levels decreased as density was raised and the suppressing effect of density was clearly stronger the greater the frequency of pea in the crop. Earlier germination and tillering ability of barley are seen as likely explanations of lower weed load in the barley dominated crop treatments.This study points at the potential of employing density and relative crop frequency as “regulators” when specific intercrop objectives such as increased competitiveness towards weeds or specific grain yield composition are wanted. |
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