Long-term P and K fertilisation strategies and balances affect soil availability indices, crop yield depression risk and N use

The last century has seen a large increase of fertiliser use, along with a subsequent rise of crop productivity. However, in many places its intensive use has become a burden to the environment, and legislation has been introduced to restrict nutrient applications. In combination with changing production scenarios as a result of climate change, this means an improved understanding is needed of how low nutrient availability and climatic stress factors affect yields and yield stability.We examined the long-term effects mineral and organic fertilisation on a nutrient-depleted field, and observed large annual variations: depending on the year, average spring barley yields under unfertilised management (U) were between 17-75% lower than the reference N1/2P1/2K1/2 (60-10-60 kg ha(-1)). Yields increased up to 174% under N1P1K1 (120-20-120 kg ha(-1)), while animal manure applications at an N availability level corresponding to N-1 were between 79 and 137%. No temporal yield trends could be observed, but long-term changes of Olsen-P and exchangeable K were related to the nutrient balances (inputs-offtake) (r(2) = 0.60 and 0.59, respectively, P < 0.001).Multiple linear regression analysis was used to examine the effects of the treatments in combination with annual weather variations. The results could be split into two outcomes, 1) a general relation between yields and temperatures for the periods of early spring (P < 0.01, multiple R-2 = 0.31) and summer (P < 0.001, multiple R-2 =0.45), and 2) an interaction between temperature and nutrient applications during crop establishment, leading to a diverse response of relative yields (P < 0.001 multiple R-2 =0.64), i.e. relative yield losses under the unfertilised treatment (U) were greater in years with lower spring temperatures, and, conversely, the increased nutrient availability in the fully mineral and organically fertilised treatments could partially alleviate the negative effects.After 13 years of repeated fertilisation, inputs were suspended for a single year and only N was applied to evaluate the residual effects. Yields were significantly affected by the different fertilisation histories (P < 0.001). Likewise, apparent nitrogen recovery tended to improve with previous inputs, but the observations were highly variable.Overall, the analyses agree with the notion that brief periods of stress at a critical stage may significantly affect yields, and confirmed that management of sufficient nutrient availability is critical for maintaining high and stable yields. (C) 2017 Elsevier B.V. All rights reserved

Long-term fertilisation strategies and form affect nutrient budgets and soil test values, soil carbon retention and crop yield resilience

AimsThe aim of this study was to evaluate the effects of long-term mineral and organic fertilisation on crop performance and soil fertility.MethodsThe Long-Term Nutrient Depletion Trial (Denmark) was used to analyse changes in concentrations of Olsen-P, exchangeable potassium (K) and soil carbon (C). Yield responses (2010-2016) were evaluatedmaking use of an early-season temperature model, fertilisation practices were evaluated by nutrient budgets, and nitrogen use efficiency by calculation of apparent recovery (ANR) in subplots receiving mineral N.ResultsOlsen-P (r(2)=0.68,

Root architecture for improved resource capture: trade-offs in complex environments

Root architecture is a promising breeding target for developing resource-efficient crops. Breeders and plant physiologists have called for root ideotypes that have narrow, deep root systems for improved water and nitrate capture, or wide, shallower root systems for better uptake of less mobile topsoil nutrients like phosphorus. Yet evidence of relationships between root architecture and crop yield is limited. Many studies focus on the response to a single constraint, despite the fact that crops are frequently exposed to multiple soil constraints. For example, in dryland soils under no-till management, topsoil nutrient stratification is an emergent profile characteristic, leading to spatial separation of water and nutrients as the soil profile dries. This results in spatio-temporal trade-offs between efficient resource capture and pre-defined root ideotypes developed to counter a single constraint. We believe there is need to identify and better understand trade-offs involved in the efficient capture of multiple, spatially disjunct soil resources. Additionally, how these trade-offs interact with genotype (root architecture), environment (soil constraints) and management (agronomy) are critical unknowns. We argue that identifying root traits that enable efficient capture of multiple soil resources under fluctuating environmental constraints is a key step towards meeting the challenges of global food security

Fertilising effect of sewage sludge ash inoculated with the phosphate-solubilising fungus Penicillium bilaiae under semi-field conditions

Sewage sludge ashes provide interesting possibilities to recycle phosphorus (P) to soil, although the immediate plant availability is often low. The objective of this work was to increase the P-fertilising effect of sewage sludge ash through inoculation with the phosphate-solubilising fungus Penicillium bilaiae. In a soil incubation study, ash amendment enhanced the content of water-extractable P, but in contrast to previous in vitro experiments, inoculation with P. bilaiae did not further increase P availability, probably due to limited competitiveness of the fungus in soil. In a micro-plot field trial, a moderate P fertiliser effect of the ash was found without any additional effect of P. bilaiae ash inoculation on plant biomass and P-uptake. However, soil microbial functions determined by the MicroResp™ method were not negatively affected by the ash amendment. In conclusion, inoculation with P. bilaiae did not prove to be a suitable strategy to enhance P availability from sewage sludge ash. A better insight into the fungus’ ecology and colonisation ability in soil and rhizosphere as well as into its interactions with ash P is needed to further develop such alternative P-fertilising approaches

Phosphate-solubilising microorganisms for improved crop productivity: a critical assessment

Phosphate-solubilising microorganisms (PSM) are often reported to have positive effects on crop productivity through enhanced phosphorus (P) nutrition. Our aim was to evaluate the validity of this concept. Most studies that report 'positive effects' of PSM on plant growth have been conducted under controlled conditions, whereas field experiments more frequently fail to demonstrate a positive response. Many studies indicate that the mechanisms seen in vitro do not translate into improved crop P nutrition in complex soil-plant systems. Furthermore, associated mechanisms are often not rigorously assessed. We suggest PSM do not mobilise sufficient P to change the crops' nutritional environment under field conditions. The current concept, in which PSM solubilise P 'for the plant' should thus be revised. Although PSM have capacity to solubilise P to meet their own need, it is the turnover of the microbial biomass that subsequently provides P to plants over a longer time. Therefore, the existing concept of PSM function is unlikely to deliver a reliable strategy for increasing crop P nutrition. A further mechanistic understanding is needed to determine how P mobilisation by PSM as a component of the whole soil community can be manipulated to become more effective for plant P nutrition