查看更多>>摘要：High quantities of pesticides are applied on vineyards. For example, the average treatment frequency index (TFI) for French vineyards was 13.5 in 2016, whereas the average TFI for wheat (a major annual crop in France) was 4.9 in 2017. Reducing pesticide use is a key issue to improve viticulture sustainability. The aims of this study were (i) to analyse the evolution of pesticide use in vineyard farms voluntarily participating in a pesticide reduction programme, and (ii) to understand the options winegrowers used to reduce their pesticide use. We analysed data from the DEPHY farm network, including 244 cropping systems followed over 10 years and spread across 12 winegrowing regions. We used the TFI to assess the intensity of pesticide use. Mean pesticide use within the network decreased over the 10-year period and mostly concerned fungicide use. By analysing several indicators such as the number of treatments and the mean TFI per fungicide treatment, we were able to identify some of the management options mobilised for achieving this pesticide reduction. The use of biocontrol products and the reduction of sprayed doses were often associated with a low TFI. The analysis of yield evolution showed a significant mean reduction, although it was smaller than the TFI reduction. This raised the question of the impact of pesticide reduction on productivity. Further trade-off analyses are required in the future.
查看更多>>摘要：In recent decades, continuous increase of N fertilizer inputs made significant contributions to the wheat pro-duction increase in the Huang-Huai-Hai Plain, the largest wheat producing region of China. However, gradually the use efficiency of N fertilizer decreased, and the increasing N rate led to a series of environment problems. A better quantitative understanding of the fates of basal N and topdressing N under water-nitrogen interactions in a wheat-soil system is essential to increase yield and reduce environmental impacts. We conducted two-year wheat experiments combining field plots and micro-plots with the l5N-labeled method under two irrigation regimens (rainfall, irrigation in jointing and anthesis) and three N rates (0, 180, and 270 kg ha(-1)). The results showed that 54.9%-70.4% of total wheat N accumulation was from soil native N, while 29.6%-45.1% was from fertilizer N. Irrigation at joint and anthesis has increased wheat N accumulation more from fertilizer N than from soil native N. Compared with rainfed condition, irrigation significantly increased plant NNI at booting and anthesis. The contribution of pre-anthesis N translocation to grain N was 80.6%-86.0%, and increased with increasing total N rate, but decreased with irrigation. The fertilizer N recovery rate increased as N rate and irrigation increased, and more N recovery occurred during jointing to anthesis period (13.1%-31.3%) than anthesis to maturity period (5.7%-10.8%) and sowing to jointing period (8.4%-8.9%). Residual fertilizer N in soil accounted for 24.5%-38.6% and decreased with increasing total N rate and irrigation. 23.6%-32.7% of fertilizer N was lost into the environment, and it decreased with increasing irrigation, but wasn't affected by total N rate. The recovery and residual for topdressing N were higher than those for basal N, whereas loss was lower. Moreover, the loss of basal N mainly occurred before jointing, and the loss of topdressing N mainly occurred from jointing to anthesis and contributed more to total N loss. These results indicated that the current wheat-soil system in Huang-Huai-Hai Plain has substantial potential to coordinate the synchronization of N demand and N supply, and finally reduce N loss. Also, this would provide critical insights to construct general crop N management models for precise N management.
查看更多>>摘要：Scientific and reasonable application of nitrogen fertiliser is an important agronomic measure to achieve both a high yield and a high quality of malting barley, and determining the appropriate nitrogen concentration is important for optimising the two. To this end, we constructed critical concentration curves for plant and ear nitrogen of malting barley as a tool for diagnosing nitrogen nutrition. Two varieties of barley, Zhepi 33 and Yangnongpi 8, were used as experimental materials, and five nitrogen application levels (ranging from 0 to 300 kg.ha(-1)) were established in three field experiments. Plant dry matter first increased and then stabilised and the nitrogen concentration increased continuously with an increase in nitrogen application rate. Based on analyses of the relationship between dry matter and nitrogen concentration, dilution models of critical nitrogen concentration in the plant (Np) and ear (Ne) of malting barley were established, and were expressed as power function equations: Np = 3.879PDM-0.444 (R-2 = 0.9705) and Ne = 2.198EDM-0.152 (R-2 = 0.7968). Next, nitrogen nutrition indexes were constructed to identify nitrogen-limiting and non-limiting treatments. To ensure an optimal grain protein concentration of 10-12%, the Ne index and the Np index were required to be 0.897-1.061 and 0.699-0.992 at the heading stage, respectively. The results provide a theoretical foundation for the diagnosis and regulation of nitrogen nutrition in malting barley and have great significance for the production of high-quality and high-yielding malting barley.
查看更多>>摘要：In the context of a warming climate and widespread soil degradation, successful soil management practices in Mediterranean vineyards should combine environmental (e.g., soil health) and productive (yield and must quality) objectives. With this objective, we tested five soil management practices in two organic farms in Chianti Classico (Italy) across three years. Five treatments were compared: conventional tillage (CT), spontaneous vegetation (S), soil-incorporated cover crop of pigeon bean (Vicia faba L. var. minor (Peterm. em. Harz) Beck. L.) (PBI), a cover crop mixture of barley (Hordeum vulgare L.) and clover (Trifolium squarrosum L.), either mulched (BCM) or incorporated in soil (BCI). We explored the effects of soil management practices on vine stress (SPAD and stem water potential), grape production (yield per plant; number of clusters per plant; cluster weight; berries weight) and must quality (titratable acidity; malic acid; pH; sugar concentration; yeast assimilable N; potential anthocyanins and total polyphenol index). Soil variability was taken into account in the statistical analysis, by testing two sets of soil covariates. A first dataset included the "raw" electrical conductivity and gamma ray total counts. The second dataset consisted in a set of soil covariates obtained by combining data collected by the proximal sensors with the results of the chemical analyses. We found that soil management affected SPAD and stem water potential with variable effects between farms and years. Mulched cover crops showed lower vine SPAD values than tilled treatments at both farms, especially in 2019 and 2020, while spontaneous vegetation effects varied considerably across farms and were comparable to tillage. Conventional tillage also decreased vine water stress compared with S, especially at the colder site in 2020. Mulched cover crops and tillage treatments had similar vine stem water potential at the warmer site. Significantly higher grape yields were found under PBI and S (about +30% compared with the other treatments), mainly due to higher cluster weight. The most productive treatments (PBI and S) also showed higher pH and malic acid concentration but lower anthocyanins and total polyphenol index as compared with the other treatments. Conventional tillage increased yeast assimilable N in 2019 while S showed the lowest values, probably due to a drop in the abundance of N-fixing plant species. On a methodological side we found that including soil parameters as covariates, instead of ECa readings and gamma ray total counts, improved regression models for all the dependent variables studied except for juice pH. Overall, our results indicate that groundcovers induced only a moderate and temporary stress that affected grape production and quality differently. While the barley-clover mixture significantly reduced grape production irrespectively of termination type, S and PBI were associated with higher grape yields. Overall, this study demonstrated that groundcovers can be profitably introduced in vineyards also in Mediterranean climates with positive effects on yields and quality.
查看更多>>摘要：The Northeast China (NEC) accounts for more than 30% of the national total maize planted area (grain yield). Adjusting the sowing dates has been considered an effective measure to adapt to climate change, but there was little evidence that how well the producers had done. In this study, we used phenology observations at 67 stations from 1981 to 2014 to detect trends in actual sowing dates, then the agricultural production systems simulator, APSIM-Maize model, was used to assess the effects of changes in observed sowing dates on maize phenology and yields. During the past 34-year period, the actual maize sowing dates show a delaying tendency, at a rate of 1-6 days per decade, but there are significant fluctuations among years. For per day delay in the sowing dates, the whole growing season was shortened by 0.1%. Delaying sowing dates reduced the solar radiation interception during the vegetative period as well as the thermal time during the reproductive period. As a result, the overall maize potential yield was negatively affected in NEC; for per day delay in the sowing dates, the potential yield was decreased by 0.6%. By contrast, advancing sowing dates in some years led to increases in both the solar radiation interception during the vegetative period and the thermal time during the reproductive period. However, these increases showed various effects on the maize potential yield across different parts of the study region. We detected a positive effect of advancing sowing dates on maize potential yield in the high latitudes, at a rate of up to 1.6%. By contrast, in the low latitudes, the negative effect of advancing sowing dates on maize potential yield was dominant, at a rate of up to 2.7%.
查看更多>>摘要：Grain protein percentage is one of the main determinants of durum wheat grain quality. However, high grain protein percentages are generally associated with low grain yields. Our aim was to identify the genotypic constraints to the realization of high grain yields with high grain nitrogen contents. To investigate this relationship, four cultivars specifically selected for their large range in 'grain yield-grain protein' relationship were compared across three seasons in a Mediterranean environment at three nitrogen (N) fertilization rates (0, 80 and 160 kg N ha(-1)). The genotypic superiority in protein percentage was consistently associated with lower number of grains m(-2) and high grain weight across years, N treatments and yield levels (from 3.5 to 8.5 t ha(-1)), whereas grain yield ranking varied with year and N treatment. A high and consistent grain protein percentage was the consequence of a high N uptake by anthesis (250 kg N ha(-1) at the higher N rate) and was consistently associated to a low grain yield. The good capacity to absorb N after anthesis, on the contrary, resulted in a grain N percentage less reliable than that obtained through a high pre-anthesis N uptake, but still high and associated with the ability to make the most of favourable weather conditions by combining a high grain N with a grain yield comparable to those of more productive cultivars. Post-anthesis N uptake and high potential grain weight are two interesting targets in breeding for high yielding, high protein cultivars.
查看更多>>摘要：Empirical decision-making on the number of plants to be sampled per experimental unit when assessing soybean grain yield is a commonly observed situation. The cause for this is unknowing how that decision affects experimental precision statistics, which has not yet been reported. Therefore, the aims of this study were: to analyze the response of experimental precision statistics as a function of the variations in the number of plants collected per experimental unit in highland and lowland systems; to define the optimal sample size per experimental unit for each precision statistic; and, to propose predictive models for estimating the precision of experiments with soybean. Field experiments were carried out in two locations of Rio Grande do Sul, Brazil, using 30 cultivars in the highland trials and 20 cultivars in the lowland trials. A validation trial was also performed using 8 cultivars. A randomized block design with three repetitions was used for all trials. The grain yield of 20 plants per experimental unit was assessed, thus totaling 9000 plants. In the validation experiment, grain yield was measured in 100 plants per experimental unit, totaling 2400 plants more. From these experiments, trials with sample scenarios of 1, 2, ..., 1000 plants per experimental unit were simulated with replacement. The confidence interval width of the precision statistics reduced as the number of plants measured per experimental unit increased, allowing a higher precision of its estimates. In general, up from values of >= 70%, precision gain, in the estimates of experimental precision statistic determined in soybean highland and lowland systems, tends to stabilize. The optimal sample number per experimental unit varied between systems and experimental precision statistics. The sampling of 18 plants per experimental unit is sufficient to estimate most precision indicators reliably. Interestingly, the mechanistic response of the confidence interval width is easily modeled and can be used for predicting experimental precision in highland and lowland cropping systems. From this analysis, a methodology for predicting experimental precision was outlined based on sample size per experimental unit, thus bringing new insight into future experimental planning for soybean experiments in highland and lowland systems in subtropical climate.
查看更多>>摘要：Wheat has been documented to be vulnerable to climate change in broad regions of the world including China. Adaptation to future climate change by breeding climate resilient cultivars is essential. However the precise information as to where, when, and what cultivar traits should be applied to adapt to climate change in the coming decades has not been available. In this study, we developed novel hybrid assessment models by incor-porating a process-based crop model and machine learning algorithms based on a large number of cultivars field experiments data. The models were applied to assess the impact of climate change on wheat productivity and to identify the timescale of wheat cultivar adaptation in the major wheat cultivation regions across China. Wheat yield was projected to decrease on average by 6.3% (9.4%) in the 2050 s under RCP 4.5 (8.5), relative to the baseline period (1986-2005), without the CO2 effect. By contrast, it was projected to increase on average by 5.7% (8.1%) in the 2050 s with the CO2 effect, across the regions and cultivar-maturing traits in China. Solar radiation, precipitation, temperature, cultivar-maturing traits, and CO2 are critical factors affecting wheat pro-ductivity in the major wheat cultivation regions. About 44% (39%) and 68% (57%) of wheat planting grids would require cultivar renewal before 2050 (2040) under RCP 4.5 and 8.5 emission scenario, respectively, at a medium risk level without the CO2 effect. The cultivars with a long reproductive growth duration, high photosynthetic efficiency and large harvest index would be generally promising although there are specific traits desirable for certain regions. This study developed a novel framework to identify the precise information on where, when, and what cultivar traits should be applied for wheat to adapt to future climate change, helping the stakeholders to cope with climate change timely and precisely.
查看更多>>摘要：Maize (Zea mays L.) yield is often reduced when the in-row plant spacing is not uniform. I used a variant of the KNMAIZE model to investigate the mechanisms responsible for the reductions. KNMAIZE determines kernels per plant from the relationship between the proportion of the assimilate supply from photosynthesis that is partitioned to the kernels and the assimilate required to sustain kernel growth. Kernels abort when their assimilate requirement exceeds the supply. Algorithms were developed to create variation of in-row plant spacing (characterized by CV) and emergence percentage. The effect of spatial variation on kernels m- 2 depended upon the ability of the dominant plants (higher plant growth rates associated with larger in-row spacing's) to increase kernels per plant to compensate for the reduction on the dominated plants (lower plant growth rates resulting from smaller in-row spacing's). When the ability of the dominant plants to respond was zero (kernels ear(-1) = florets ear(-1), excess capacity = 0), kernels m(-2) started decreasing as soon as the CV 0. When the dominant plants had excess capacity (i.e., kernels per ear < florets per ear), the beginning of the decline occurred at progressively larger CVs depending upon the magnitude of the excess capacity. Populations greater than the minimum needed for maximum yield provide the excess capacity on dominant plants to buffer kernels m(-2) and yield against variation of in-row spacing and reductions in emergence.
查看更多>>摘要：Cover crop (CC) mixtures appear as a promising agroecological tool for weed management. Although CC supress weed growth by competing for resources, their suppressive effect under contrasting levels of soil resource availability remains poorly documented. A two field:year experiment was conducted to investigate the weed suppressive effect of four CC mixtures. They were composed of 2 or 8 species including or not legume species and compared to a bare soil control. The experiment included two levels of irrigation and nitrogen fertilisation at CC sowing. The objectives were to assess (i) weed and CC aboveground biomass response to CC mixtures and resource availability, (ii) the weed suppressive effect of CC mixtures across a gradient of CC biomass and (iii) weed community response to CC mixtures and resource availability. CC and weed biomass were mainly influenced by interactions between CC mixtures and fertilisation and between CC mixtures and irrigation, with contrasted effects between field:years. Nitrogen fertilisation increased biomass of non-legume based CC mixtures but this only resulted into a further reduction of weed biomass of little biological relevance. Legume-based CC mixtures suppressed weeds to a greater extent without nitrogen fertilisation in year 2 but not in year 1, possibly due to contrasted initial soil nitrogen availability (lower in year 2). Weed biomass generally benefited more from irrigation than CC mixtures. Among the 33 weed species recorded, weed communities in each plot were dominated by wheat volunteers, Geranium dissectum, Veronica persica and Echinochloa crus-galli, whose biomass varied depending on the interaction between year, CC mixture and resource availability. Our results revealed that competitive outcomes between CC mixtures and weed species were driven by a complex interaction between resource availability and species traits. Further experiments focusing on plant traits should improve our understanding of weed:CC competitive outcomes under various levels of resource availability.
NSTL
Elsevier