Azodyn: a simple model simulating the date of nitrogen deficiency for decision support in wheat fertilization

A dynamic soil–crop model was developed to predict the date on which N deficiency occurs for winter wheat crops in the temperate climate of Northwest Europe. It is based on the daily simulation of soil N supply and crop N requirement for the period during which N-fertilizer is usually applied to wheat crops, the end of winter until flowering. The soil sub-model was derived from the `balance-sheet method' used in France for nitrogen fertilization recommendations. It describes the net mineralization of various sources of organic matter (soil humus, crop residues, organic products). The crop sub-model simulates crop biomass production and its nitrogen content using a radiation use efficiency model and a critical dilution curve for nitrogen content. Both soil and crop sub-models require few parameters and inputs, most of which are readily available on commercial farms, together with daily climatic data. The model tested with various rates and timings of N application in three experiments accurately simulated the date on which nitrogen deficiency began in wheat crops. The interest in using the model for tactical and strategic approaches is discussed.     

Farmers' seed management practices open up new base populations for pearl millet breeding in a semi-arid zone of India

Farmers in western Rajasthan (north‐west India) produce and maintain their landrace populations of pearl millet through their own distinct seed management practices. The objective of this study was to characterize morphological and agronomic variability of different traits between and within three farmers' populations using quantitative‐genetic parameters. Populations examined were a typical landrace and two modified landraces, which were generated through farmer introgression of modern varieties with different levels of subsequent selection. From these three populations, 100 random full‐sib progenies were evaluated in field trials at two locations in western Rajasthan over two years. Significant genetic variation existed within the three populations. Estimates of heritability were moderate to high for all observed traits. Predicted selection response for grain yield across environments was 1.6% for the typical landrace and 2.2% for both the modified landraces. Results suggest that the introgression of modern varieties into landraces had increased the genetic diversity. Therefore, farmers' current breeding activities could open up new resources for plant breeding programmes aiming at plant improvement for the semiarid zones of India.     

Combining the simulation crop model AquaCrop with an economic model for the optimization of irrigation management at farm level

Water resources used in irrigated agriculture are increasingly scarce, particularly in many countries where irrigation has undergone recent expansion. To optimize the limited resources available, optimization models provide useful tools for technical and economic analyses. One of the key inputs of these models is the yield response to water which is often simulated with empirical water production functions. At present, dynamic crop simulation models, such as AquaCrop (Steduto et al., 2009) offer alternative predictions of crop responses to different irrigation strategies as inputs to economic optimization. A model at farm scale was developed and applied to an area in South-western Spain to assist farmers in pre-season decision making on cropping patterns and on irrigation strategies. Yield predictions were obtained from the AquaCrop model which was validated for four different crops. The model simulated the impact on farm income of: (a) irrigation water constraints; (b) variations in agricultural policies; (c) changes in product and water prices; and, (d) variations in the communication to farmers of the specific level of irrigation water allocation. The applications of the models to the study area showed that currently, the changes in cropping patterns induced by the agricultural policy will encourage water savings more than an increase in water prices. Under water restrictions, the best strategy combines planting of low water use crops in part of the area to release water to grow more profitable crops with greater water needs. The model predicted a strong negative impact on farm income of delaying a decision on the level of seasonal water allocation by the water authority, reaching up to 300 € ha⁻¹ in the case of the study area.     

Assessing the adaptability and stability of new pearl millet hybrids for grain yield,grain iron and zinc content in Ghana using AMMI analysis

Journal of Crop Science and Biotechnology - Twenty-four pearl millet (Pennisetum glaucum (L) R. Br) single-cross hybrids were evaluated at four environments of northern Ghana during the 2018 and...     

SPN: A model for the study of soil-plant nitrogen fluxes in silage maize cultivation

The aim of this study was to adapt the Soil-Plant-Nitrogen (SPN) model to silage maize, as an explorative tool for evaluating the possibility of expanding maize cultivation to regions which historically have been too cold for maize production, and for estimating the effects of management practices as fertiliser and manure application on C and N fluxes. The model was validated using data from a 5-year maize experiment conducted in northern Germany. Available observations included shoot biomass and N yield, soil mineral N (0–90 cm) sampled in spring and autumn, and nitrate in the soil solution during winter; occasionally also the soil water content and ground water level were recorded. The SPN crop module, originally developed for barley production in Norway, was successfully adapted to maize. The strategy adopted was to assess the maize-specific algorithms for the radiation use efficiency (RUE) and the leaf area index (LAI) by statistical analysis of selected subsets of the available observations. In addition, parameters were modified with respect to crops characteristics. The baseline mineralisation of the SPN soil module was inspected with respect to the ability to predict both the observed plant N uptake and soil mineral N of the unfertilised plots. In order to predict the time course of plant N uptake it was necessary to incorporate a ploughing effect, as a transient mineralisation burst. The modified SPN was evaluated with respect to the whole range of mineral N and cattle slurry treatments. Nitrogen and biomass yields were successfully predicted. The dynamicity of the soil mineral N prediction was reasonable, but a statistical analysis of the model performance was hampered by the selective timing of the soil samples. The good fit of the time course of the plant N uptake under contrasting fertiliser treatments suggests that the predictions of soil N immobilisation and losses can also be assumed to be reasonable. The SPN model seems a suitable tool for the prediction of the effects of climate and management on the yield and on the soil-plant N economy of silage maize. However, under extreme combination of high radiation and low temperature or vice-versa, RUE estimation may be a source of uncertainty and more empirical studies are recommended.     

Contrasting the spatial management of nitrogen and phosphorus for improved water quality: Modelling studies in New Zealand and France

Critical source areas (CSAs) define areas of a farm or catchment that emit the majority of water quality contaminants but account for a minority of the area at a field, farm or catchment scale. Using process based modelling we tested the hypothesis that the definition and management of CSAs would decrease losses of phosphorus (P) in two New Zealand catchments and nitrogen (N) in a French catchment. In the New Zealand catchment, CSAs of P loss were isolated to small areas within fields commensurate with surface flow pathways, while in the French catchment, CSAs for N loss were influenced by factors (inputs and land use) relevant at a field (or multiple field) scale. Scenarios were tested that examined the management of CSAs versus whole field management for P, and decreasing N loss within CSAs by increasing the proportion of grassland fields and changing their location relative to cropland. The results showed that N losses decreased by up to 25% as more grassland was incorporated into the catchment, especially in wet areas near valley bottoms due to a longer growth period and better utilisation/storage of N than cropland. For P, focusing mitigation on CSAs decreased catchment losses to a similar degree as mitigations applied across the whole catchment, but was on average 6–7 times more cost-effective. Therefore, the definition and management of CSAs at an appropriate scale is recommended to improve water quality and minimise the impact on farm profitability.     

Integrating simulation data from a crop model in the development of an agri-environmental indicator for soil cover in Switzerland

Agriculture generates important impacts on the environment, which can be evaluated with agri-environmental indicators. A key element of environment protection in agriculture is the maintenance of a dense soil cover for the longest possible period. Notably, soil cover is known to diminish erosion risks and nitrate leaching. In this study, an agri-environmental indicator for soil cover is presented, which integrates data from the crop model STICS to quantify vegetation growth dynamics. Simulations were conducted with STICS for the major crops cultivated in Switzerland across several contrasting pedoclimatic situations. They were then integrated with data for crop residue cover to evaluate soil cover at the field and farm levels in the framework of a farm network survey. At the field level, for the period from the harvest of the previous crop through the harvest of the main crop, the highest soil cover was achieved by silage maize and winter barley. A high variability between fields was observed, due to the diversity of cultural practices during the period preceding the seeding of the main crops. Some crops, winter wheat in particular, showed a high number of days with insufficient soil cover (under 30%), leading to potential environmental risks. This shows the crucial need of promoting conservation agriculture principles (permanent soil cover, minimum soil disturbance, diversification of crop rotation) in arable systems to better protect the soils and the environment. The soil cover indicator presented here provided a continuous quantification of soil cover, whereas most of the currently used indicators provide qualitative or roughly quantitative results.     

Changes in the meiotic pairing behaviour of a winter wheat-winter barley hybrid maintained for a long term in tissue culture, and tracing the barley chromatin in the progeny using GISH and SSR markers

The aim of the present study was to produce backcross progenies in a new winter wheat (‘Asakaze komugi’) × winter barley (‘Manas’) hybrid produced in Martonvasar. As no backcross seeds were obtained from the initial hybrids, young inflorescences of the hybrids were used for in vitro multiplication in three consecutive cycles until a backcross progeny was developed. The chromosome constitution of the regenerated hybrids was analysed using genomic in situ hybridization (GISH) after each in vitro multiplication cycle. The seven barley chromosomes were present even after the third in vitro multiplication cycle but abnormalities were observed. Sixteen BC; plants containing, according to GfSH analysis, one to three complete barley chromosomes, two deletion barley chromosomes and a dicentric wheat‐barley translocation were grown to maturity from the single backcross progeny. The barley chromatin was identified using 20 chromosome‐specific barley SSR markers. All seven barley chromosomes were represented in the BC: plants. A deletion breakpoint at FL ±0,3 on the 5HL chromosome arm facilitated the physical localization of microsatellite markers.     

Physiological and anatomical traits associated with tolerance to long‐term partial submergence stress in the Lotus genus: responses of forage species,a model and an interspecific hybrid

Cattle production based on natural pastures is often subject to flooding periods, which affect plant performance and as a result, forage production. Although most forage legumes are not tolerant to flooding, Lotus spp. are outstanding alternatives, since species, such as L. tenuis (Lt) and L. corniculatus (LcT), have high forage quality and are adaptable to different environments. We recently obtained a L. tenuis × L. corniculatus hybrid (LtxLc) with potential new cultivar traits, although its tolerance to flooding stress has not yet been evaluated. In the present study, the performance of LtxLc, its parental diploid accessions, the model legume L. japonicus and tetraploid LcT were evaluated under 55 days of partial submergence stress and a 35‐day recovery period. Physiological, morphological and anatomical traits were analysed, showing that tolerance to partial submergence was positively associated with aerenchyma and adventitious root formation and relative growth rates. Overall, Lt and LtxLc showed the best responses under stress and during the recovery period. Nevertheless, the higher forage value of LtxLc makes it recommendable for use in environments affected by flooding. Our results could be used as breeding criteria for the generation of new cultivars tolerant to partial submergence stress.     

Social and political barriers to the use of Marine Protected Areas for conservation and fishery management in Melanesia

Abstract: In this paper we examine the strengths and weaknesses of state‐supported Customary Marine Tenure (CMT) systems in two independent Melanesian states (Solomon Islands and Papua New Guinea) in the context of the management of rapidly intensifying commercial and subsistence fisheries. We focus particularly on the proposed use of permanent no‐take Marine Protected Areas (MPAs), which are at present strongly favoured by scientists and environmentalists around the world, as the most versatile marine fishery management tool, especially in poor developing countries. We argue that, with some exceptions, typical Melanesian CMT regimes make MPAs difficult to establish, primarily due to issues of scale. We look closely at the ecological rationale for no‐take MPAs, for different coral‐reef based species, and assess the likelihood that populations of these species are self‐replacing on the same scale as CMT territories for most of coastal PNG and Solomon Islands. We argue that with some exceptions (mainly species with short‐lived larvae), the dynamics and scale of population replacement processes for most fished species make no‐take permanent closures largely incompatible with traditional CMT systems, and therefore unlikely to prove a successful management tool in this socio‐political context.     

Integrated Approach to the Vital Mechanism Theory and Ant Colony Algorithm for Optimized Land Use Allocation: A Case Study of the Liangjiang New Area in Chongqing

Optimal allocation of land use is essential to promote regional economic and social development.However,research on such allocations in development zones is limited.This paper proposes a new land use allocation method for development zones and tests its feasibility.Based on prior research,this study predicts the developmental stage of a development zone and sets the objective functions and constraint conditions accordingly.This paper then measures the conversion relationship between the land use types in an unit according to the land use suitability results and the vital mechanism theory and uses the ant colony algorithm to construct a land use optimization model on the basis of this conversion relatonship.The model is then applied successfully to a case study of the Liangjiang New Area,Chongqing,China.The results show that the vital mechanism theory better reflects the relationship between land use types.The economic benefits increase 3.5 times and compactness improves by 46.5%between the initial year(2009)and the optimized year(2020),after the proposed model is applied.