Specific and Intraspecific P Efficiency of Small-Grain Legumes as Affected by Long-Term P Management

Abstract

Legumes have a high demand for phosphorus (P) but also have effective physiological and morphological strategies of P mobilisation. In order to evaluate the inter- and intraspecific P efficiency of small-grain legumes under contrasting long-term P management, eight accessions each of alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were cultivated in two consecutive growing periods from 2020 to 2021 in a field trial established in 1998. Six treatments (no P, triple-superphosphate (TSP), biomass ash, cattle manure, biowaste compost, and biowaste compost + TSP) were considered as P sources. While the yield clearly varied between both growing seasons, the differences between alfalfa and red clover were relatively small (4.7 vs. 4.9 Mg ha−1 in 2020 and 12.0 vs. 10.5 Mg ha−1 in 2021, p < 0.05). Even after more than 20 years of P management, crop yields were hardly affected by mineral P sources (TSP and biomass ash) while organic fertilisers increased the yields and nutrient uptake of plants and also raised soil P pools and the activities of soil enzymes in comparison to the control. A relevant crop effect was only found for the nitrogen (N) leaching with higher mineral N contents in 60 to 90 cm soil depth measured for red clover compared to alfalfa (11.8 vs. 4.8 kg ha−1, p < 0.05). Our results emphasise the high P efficiency of small-grain legumes without pronounced inter- or intraspecific differences. The yield-enhancing effect of organic amendments was related to higher soil fertility rather than to P supply.

Assessment of Inter- and Intraspecific P Efficiency in Forage Legumes as Affected by Recycling Fertiliser

“…Apart from accession LE2812, other alfalfa accessions were originally from European countries and showed similar yield and nutrient uptakes. Red clover accession LE1391, which was tested in both PE1 and PE2, showed high biomass and high nutrient uptake, which is in agreement with the result in our field study [35]. The constant performance of accession LE1391 in controlled and field conditions underlines its agronomic value, and it could be recommended as a suitable candidate for cultivation as a forage legume in Europe.…”

“…This means that this accession has a high P uptake efficiency when growing under favourable conditions in terms of temperature and lighting. However, results from a field trial in north-eastern Germany show that relatively cool weather conditions can limit the growth of this accession [35]. Apart from accession LE2812, other alfalfa accessions were originally from European countries and showed similar yield and nutrient uptakes.…”

“…In addition, the supplied compost increased the readily available P fraction in soil, as the readily available P fraction usually constitutes the largest fraction in the compost [81]. The fertiliser effect of the same compost on alfalfa and red clover (as well as the effect of TSP) was also investigated in a two-year field study based on a long-term field experiment [35]. In the field, compost In contrast to the other recycling products, compost contains relevant amounts of N. However, the higher N supply of compost did not lead to higher N concentrations in the legumes.…”

“…Additionally, previous genotypic research on alfalfa and red clover accessions has focused primarily on forage yield, nutritional value and stress tolerance [31][32][33][34], while little attention has been paid to their intraspecific variations in P utilisation with different P supplies. Our previous field study directly compared P uptake and efficiency between various alfalfa and red clover accessions, as affected by long-term P management, for the first time [35], revealing low inter-and intraspecific P efficiencies. This led us to hypothesize that a greater diversity of P sources and a higher gradient of P supply is necessary to identify accessions that differ in their P efficiency.…”