Nitrogen Fertilizer Effects on Pea–Barley Intercrop Productivity Compared to Sole Crops in Denmark

Abstract

Cereal–legume intercropping increases the nitrogen (N) input from biological nitrogen fixation (BNF) and improves the exploitation of fertilizer and soil N, often leading to higher grain N content and higher productivity per unit land area compared to monocrops. Previous studies have found that these effects are more tangible under low soil and fertilizer N conditions compared to high N availability, and there is a need to assess the N uptake at critical crop development stages in order to time the N application for maximum uptake and use efficiency. The objective of this study was to assess the productivity of pea–barley intercropping compared to monocropping under 0 kg N ha−1 (0 N) and 100 kg N ha−1 (100 N). In 2017, a split plot experimental design was implemented with pea (Pisum sativum) sole crop (SC pea), barley (Hordeum vulgare) sole crop (SC barley), and pea–barley intercrop (IC total) as the main plots and 100 N applications in two 50 kg N ha−1 splits at 30 and 60 days after emergence as subplots within the main plots. The Land Equivalent Ratio (LER), based on grain dry matter (GDM) yields in the pea–barley intercrop (IC total), was higher (1.14 at 0 N and 1.10 at 100 N), indicating 10–14% greater radiation, nutrient, and water use efficiency compared to the sole crops and 4% greater resource use efficiency at 0 N compared to the 100 N; this illustrated greater total intercrop productivity compared to sole crops. The 100 N treatment decreased the SC pea and pea in intercrop (IC pea) GDM and grain dry matter N (GDMN) and increased the GDM and GDMN in SC barley and barley in the intercrop (IC barley). Intercropping increased the grain N content and therefore the protein content of the grains in 0 N and 100 N treatments. The highest fertilizer N yield, % nitrogen derived from fertilizer (%NDFF), and % nitrogen use efficiency (%NUE) were achieved in SC barley followed by IC total, indicating that intercropping improved the soil and fertilizer N use compared to SC pea. The IC pea increased the % nitrogen derived from atmosphere (%NDFA) from 67.9% in SC pea to 70.1% in IC pea. IC total increased the share of %NDFF, %NDFS, and %NDFA compared to the SC pea, which indicated a significant advantage of intercropping due to the complementarity of the component species under limited N supply in the field.

Biomass and Protein Yields of Field Peas and Oats Intercrop Affected by Sowing Norms and Nitrogen Fertilizer at Two Different Stages of Growth

“…Nitrogen fertilizer increased biomass and hay yields for sole crops and their mixtures. Similar findings have been recorded in other researches [9]. Analysis has shown that nitrogen fertilizer has a pronounced effect on the biomass and hay yield of oats compared to field peas.…”

“…The most significant advantages of intercropping legumes and cereals or grasses are the increased yields compared to sole stands [4][5][6][7], and better and more balanced biomass quality regarding proteins and energy [8]. Intercropped species better utilize nitrogen and other nutrients from the soil [9,10], as well as soil moisture and solar radiation, while other research highlights the benefits on the soil microorganisms [11]. The research thus far mentions several other benefits and, in particular, nitrogen transfer from the roots of legumes to the roots of different cereals or grasses [12][13][14].…”

Inorganic Nitrogen Transport and Assimilation in Pea (Pisum sativum)

“…Pea appears to store less vacuolar NO 3 − than non-legume species and increasing this storage capacity may be a useful target for improving NUE, providing the crop with a reservoir of N to sustain short-term requirements for growth. In intercropping systems, for example pea with barley, there is evidence that NUE is improved relative to a single pea crop [ 77 ]. Like other legumes, pea should have less dependence on N uptake from soil, with an optional N supply fixed by nodules.…”

Effect of sowing proportion on above- and below-ground competition in maize–soybean intercrops

“…The oven-dried samples were put in small plastic bags after grinding. The study of N and P uptake are the most common among mineral elements 55 , 56 . Concentrations of N and P in the plant dry matter were determined after digestion with H 2 SO 4 and H 2 O 2 ; N concentration was measured according to the Kjeldahl method 20 , whereas P concentration was measured by the molybdenum-antimony anti-spectrophotometric method 16 .…”