Carbon assimilation,leaf area dynamics,and grain yield in contemporary earlier- and later-senescing maize hybrids

Maize breeding during the past 50 years has been associated with a delay of leaf senescence, but it is not clear whether this trait is likewise associated with higher grain yield in modern hybrids. Post-silking growth, leaf area dynamics, photosynthetic parameters and yield were compared in modern maize hybrids differing in canopy senescence rate. In the first two experiments, four hybrids were grown in the field at Balcarce, Argentina (37°45′ S, 58°18 W). In spite of differences in chlorophyll retention and photosynthesis of the ear leaf, post-silking growth and grain yield were very similar in all four hybrids while kernel N concentration was lower in the later-senescing hybrids. In a third experiment, a later-senescing (NK870) and an earlier-senescing (DK682) hybrid were grown to analyze the potential photosynthetic contribution of delayed leaf senescence. Leaf area and chlorophyll content were larger in NK870, especially at the lower canopy level (0.75 m above the ground). However, hybrids did not differ for canopy light interception. Because photosynthetic photon flux density below 1 m above the ground was less than 10% of incident radiation and photosynthesis quantum yield did not change during senescence, the potential photosynthetic output of lower leaves below 1 m was very low. Lower leaves of NK870 had N concentrations higher than those needed to sustain photosynthesis at the light conditions below 1 m. Therefore, we show that delayed senescence does not necessarily improve post-silking C accumulation because: (i) canopy light interception is not reduced by senescence except at very late stages of grain filling; (ii) contrasting hybrids show more pronounced senescence differences at canopy levels receiving less than 10% of incident radiation; (iii) delayed senescing hybrids present lower kernel N concentrations while extra N is retained in leaves exposed to a light limiting micro-environment. Delayed senescence at lower canopy levels may be unproductive, at least under non-stressing conditions.     

Carbon and nitrogen allocation and grain filling in three maize hybrids differing in leaf senescence

Between flowering and maturity, leaf senescence reduces green leaf area while grains are filled from photosynthesis, nitrogen (N) uptake by roots and remobilisation from shoots. The question arises of possible effects of leaf senescence on photosynthesis, N uptake and remobilisation and their modification through genetic variations in senescence. To address this question, we compared three cultivars showing different behaviours. Tarro and Nicco are two modern hybrids presenting the same important grain sink but showing different time course of senescence, the former being normally senescent the latter “stay-green”. Déa hybrid, very well known by many previous experiments was the reference hybrid.The purpose was to monitor precisely the carbon (C) and N repartition in the main organs of the plant in connection with the progress of leaf senescence (experiment 1) and to measure the changes created by variations of N supply and soil-climate conditions (experiment 2).In experiment 1, time course of leaf senescence of the different leaf stages and weight of leaves, shoots and grains and N concentration of shoots and grain were measured weekly. In experiment 2, the same three cultivars were grown at limiting and non-limiting N supply in four locations in France during 2 years. At flowering, silage and harvest stage, dry matter and N concentration were measured in the main parts of the plant, and leaf senescence was evaluated at silage stage.On soil well supplied with N, Tarro had an identical rate of leaf senescence than Nicco for leaves below the ear, but higher for leaves above the ear. After flowering, Nicco accumulated more biomass than Tarro, but kept a larger part of this total biomass in the stem. In contrast, Tarro accumulated a larger part of total biomass in the grain.After flowering, N uptake was larger in Nicco than Tarro. Shoot N concentration decreased earlier and more completely in Tarro than Nicco, indicating a larger remobilisation to the grain. Though Tarro began and finished grain filling simultaneously with Nicco, it reached 70% of final grain weight 25 °C d sooner than Nicco.The senescence due to N stress differed from the physiological senescence of a senescent hybrid. The time course of the reproductive phase and the N repartition in the plant suggest that a threshold in grain filling or in shoot nitrogen decrease could be the internal signal triggering senescence of uppermost leaves.     

Mechanical control of clover improves nitrogen supply and growth of wheat in winter wheat/white clover intercropping

The major objective for clover in a winter wheat/white clover intercropping system is to supply nitrogen (N) for the wheat. A field experiment was repeated in 2 years on a loamy sand in Denmark to investigate the possibilities for increasing N supply to the winter wheat by cutting and mulching the clover between the wheat rows. The clover was cut with a weed brusher on three different dates in each year.Intercropped wheat with unbrushed clover had a lower grain yield than wheat as a sole crop. Brushing increased wheat N uptake and wheat grain yields. Intercropping with two or three brushing dates gave higher wheat yields than wheat as the sole crop. The largest increases in grain N uptake, 21–25 kg N ha⁻¹, were obtained for the brushings around wheat flag leaf emergence. The highest yield increases with a single brushing, 0.98–1.11 Mg DM ha⁻¹, were obtained when brushing was performed during the stem elongation phase. The largest grain yields for treatments with two brushings were obtained with a first brushing at start of stem elongation and a second around flag leaf emergence. The first brushing probably provided N to increase the wheat leaf area index and thus the light interception, while the second brushing provided N to sustain the leaf area during grain filling and reduced clover biomass and therefore competition for water. Intercropping wheat and clover increased grain N concentrations by 0.11–0.39%-point compared with wheat as a sole crop. Intercropping may thus offer possibilities for improving the bread-making quality of organically grown wheat.     

Application of low intensity light pulses to delay postharvest senescence of Ocimum basilicum leaves

Fresh basil (Ocimum basilicum L.) is a highly perishable leafy green vegetable with a storage life of 4–5 d at room temperature. Exposure of basil leaves to temperatures below 12 °C during storage results in chilling injury; therefore, refrigeration cannot be used to extend postharvest life of basil. Typically, leafy vegetables are stored in darkness or extremely low irradiance. Darkness is known to induce senescence, and the initial phase of senescence is reversible by exposure to light. In this work, we studied the effects of low-intensity white light pulses at room temperature on postharvest senescence of basil leaves. Daily exposure for 2 h to 30–37 μmol m⁻² s⁻¹ of light was effective to delay postharvest senescence of basil leaves. Chlorophyll and protein levels decreased, ammonium accumulated and leaves developed visual symptoms of deterioration (darkening) during storage in darkness. Light pulses reduced the intensity of these senescence symptoms. The photosynthesis light compensation point of basil leaves was 50 μmol m⁻² s⁻¹ i.e., higher than the intensity used in this study, and the effect of treatment with red light was the same as with white light, while far red light was ineffective. Light pulses exerted a local effect on chlorophyll loss, but the effect on protein degradation was systemic (i.e., spreading beyond the illuminated parts of the leaf blade). The results of this study indicate that daily treatment for 2 h with low intensity light (30–37 μmol m⁻² s⁻¹ every day) during storage at 20 °C is an effective treatment to delay postharvest senescence of basil leaves. The delay of postharvest senescence by low intensity light pulses seems to be mediated by phytochromes, and it is systemic for protein, and partially systemic for chlorophyll degradation.     

Growth and yield of winter wheat in the first 3 years of a monoculture under varying N fertilization in NW Germany

Different preceding crops interact with almost all husbandry and have a major effect on crop yields. In order to quantify the yield response of winter wheat, a field trial with different preceding crop combinations (oilseed rape (OSR)–OSR–OSR–wheat–wheat–wheat), two sowing dates (mid/end of September, mid/end of October) and 16 mineral nitrogen (N) treatments (80–320 kg N ha⁻¹) during 1993/1994–1998/1999, was carried out at Hohenschulen Experimental Station near Kiel in NW Germany. Single plant biomass, tiller numbers m⁻², biomass m⁻², grain yield and yield components at harvest were investigated. During the growing season, the incidence of root rot (Gaeumannomyces graminis) was observed. Additionally, a bioassay with Lemna minor was used to identify the presence of allelochemicals in the soil after different preceding crops.Averaged over all years and all other treatments, wheat following OSR achieved nearly 9.5 t ha⁻¹, whereas the second wheat crop following wheat yielded about 0.9 t ha⁻¹ and the third wheat crop following 2 years of wheat about 1.9 t ha⁻¹ less compared with wheat after OSR. A delay of the sowing date only marginally decreased grain yield by 0.2 t ha⁻¹. Nitrogen fertilization increased grain yield after all preceding crop combinations, but at different levels. Wheat grown after OSR reached its maximum yield of 9.7 t ha⁻¹ with 210 kg N ha⁻¹. The third wheat crop required a N amount of 270 kg N ha⁻¹ to achieve its yield maximum of 8.0 t ha⁻¹.Yield losses were mainly caused by a lower ear density and a reduced thousand grain weight. About 4 weeks after plant establishment, single wheat plants following OSR accumulated more biomass compared to plants grown after wheat. Plants from the third wheat crop were smallest. This range of the preceding crop combinations was similar at all sampling dates throughout the growing season.Root rot occurred only at a low level and was excluded to cause the yield losses. The Lemna bioassay suggested the presence of allelochemicals, which might have been one reason for the poor single plant development in autumn.An increased N fertilization compensated for the lower number of ears m⁻² and partly reduced the yield losses due to the unfavorable preceding crop combination. However, it was not possible to completely compensate for the detrimental influences of an unfavorable preceding crop on the grain yield of the subsequent wheat crop.     

Tree-crop interactions in maize-eucalypt woodlot systems in southern Rwanda

We studied the interaction between Eucalyptus saligna woodlots and maize crop in southern Rwanda. Three sites were selected and in each, a eucalypt woodlot with mature trees and a suitable adjoining crop field of 12.75 m × 30 m was selected. This was split into two plots of 6 m × 12 m and further subdivided into nine sub-plots running parallel to the tree-crop interface. Maize was grown in both 6 m × 12 m plots and one of these received fertiliser. Soil moisture, nutrients and solar radiation were significantly reduced near the woodlots, diminishing grain yield by 80% in the 10.5 m crop-field strip next to the woodlot. This reduction however affects only 10.5% of the maize crop field, leaving 89.5% unaffected. Spreading the loss to a hectare crop field, leads to an actual yield loss of 0.21 t ha⁻¹, equivalent to 8.4%. Expressing yield loss in tree-crop systems usually presented as a percentage of yield recorded near the trees to that obtained in open areas may be misleading. Actual yields should be reported with corresponding crop field areas affected. Variation in grain yield coincided with those for soil moisture, soil N and K; all increasing from the woodlot-maize interface up to 10.5 m and remaining similar to the values in open areas thereafter. Solar radiation continued to increase with distance up to 18 m from the woodlot-maize interface. Harvest index in unfertilised maize exceeded that in the fertilised treatment reflecting the crop’s strategy to allocate resources to grain production under unfavourable conditions. Fertilisation increased maize yield from 1.3–2.6 t ha⁻¹ but the trend in the woodlot effects on maize remained unaltered.     

Performance and application of the APSIM Nwheat model in the Netherlands

APSIM Nwheat is a crop system simulation model, consisting of modules that incorporate aspects of soil water, nitrogen (N), crop residues, and crop growth and development. The model was applied to simulate above- and below-ground growth, grain yield, water and N uptake, and soil water and soil N of wheat crops in the Netherlands. Model outputs were compared with detailed measurements of field experiments from three locations with two different soil types. The experiments covered two seasons and a range of N-fertiliser applications. The overall APSIM Nwheat model simulations of soil mineral N, N uptake, shoot growth, phenology, kernels m⁻², specific grain weight and grain N were acceptable. Grain yields (dry weight) and grain protein concentrations were well simulated with a root mean square deviation (RMSD) of 0.8 t ha⁻¹ and 1.6 protein%, respectively. Additionally, the model simulations were compared with grain yields from a long-term winter wheat experiment with different N applications, two additional N experiments and regional grain yield records. The model reproduced the general effects of N treatments on yields. Simulations showed a good consistency with the higher yields of the long-term experiment, but overpredicted the lower yields. Simulations and earlier regional yields differed, but they showed uniformity for the last decade.In a simulation experiment, the APSIM Nwheat model was used with historical weather data to study the relationship between rate and timing of N fertiliser and grain yield, grain protein and soil residual N. A median grain yield of 4.5 t ha⁻¹ was achieved without applying fertiliser, utilising mineral soil N from previous seasons, from mineralisation and N deposition. Application of N fertiliser in February to increase soil mineral N to 140 kg N ha⁻¹ improved the median yield to 7.8 t ha⁻¹ but had little effect on grain protein concentration with a range of 8–10%. Nitrogen applications at tillering and the beginning of stem elongation further increased grain yield and in particular grain protein, but did not affect soil residual N, except in a year with low rainfall during stem elongation. A late N application at flag leaf stage increased grain protein content by several per cent. This increase had only a small effect on grain yield and did not increase soil residual N with up to 40 kg N ha⁻¹ applied, except when N uptake was limited by low rainfall in the period after the flag leaf stage. The economic and environmental optima in winter wheat were identified with up to 140 kg N ha⁻¹ in February, 90 kg N ha⁻¹ between tillering and beginning of stem elongation and 40 kg N ha⁻¹ at flag leaf stage resulting in a median of 8.5 t ha⁻¹ grain yield, 14.0% grain protein and 13 kg N ha⁻¹ soil residual N after the harvest. The maximum simulated yield with maximum N input from two locations in the Netherlands was 9.9 t ha⁻¹.     

Effects of varying nitrogen fertilization on crop yield and grain quality of emmer grown in a typical Mediterranean environment in central Italy

Experiments were carried out to study the effects of N fertilizer rates and timing of application on the yield and grain quality of a rainfed emmer crop (Triticum dicoccum Shübler) under Mediterranean conditions. The following parameters were analyzed: hulled and net grain yield, hulled index, spikes m^?2, spikelets per spike, kernels m^?2, thousand-kernel weight, biomass, plant height, lodging, grain protein and ash content. In the first experiment, different N rates (30, 60 and 90 kg N ha^?1 plus a control not fertilized) were split at three phenological stages (seeding 20%, tillering 40% and stem elongation 40%). In the second experiment, three N doses (30, 60 and 90 kg N ha^?1) were applied to three crop stages (seeding, tillering and stem elongation). In the third experiment, the rate of 90 kg N ha^?1 was distributed in different amounts (90-0-0, 0-90-0, 0-0-90, 45-45-0, 45-0-45, 0-45-45, 30-30-30) at the three mentioned crop stages. Increasing N rates resulted in higher hulled and net grain yield, as well as protein content. Fertilization (from 60 to 90 kg N ha^?1) applied to tillering maximized hulled and net grain yield. Fertilization (90 kg N ha^?1) applied to stem elongation gave the highest grain protein content (%) while splitting application (30 kg N ha^?1 each) at three phenological stages maximized protein yield per hectare. Application of half or one-third of 90 kg N ha^?1 to stem elongation improved grain protein content in comparison with applications at sowing, or at both sowing and tillering. The main factor determining higher yields with increasing N rates in this emmer crop was the number of kernels m^?2. None of the yield components accounted for differences in grain yield when timing and splitting application were varied.     

Toward yield improvement of early-season rice: Other options under double rice-cropping system in central China

Rice (Oryza sativa L.) grain yields vary considerably between seasons under subtropical irrigated conditions. Reports on comparisons of grain yield between early- and late-season rice in subtropical environments are lacking. In order to evaluate the role of climatic and physiological factors under double rice-cropping system in determining rice grain yield in farmers’ fields, six field experiments were conducted in both early and late seasons from 2008 to 2010 in Wuxue County, Hubei province, China. For early season crop, the attainable yield was highest under dense planting (38.5 hills m⁻²) when N was applied at a rate of 120–180 kg ha⁻¹. However, the effect of hill density on grain yield was relatively smaller for late season crop, while moderate hill density (28.1 hills m⁻²) and nitrogen rate (120 kg ha⁻¹) were advantageous in terms of grain yield and lodging resistance. Remarkably higher grain yields were achieved in late season crops compared with early season crops, as the former had superiority over the latter in sink size (sink capacity, such as spikelets per m²) and biomass production. The comparatively lower yield under early season mainly resulted from slower growth during the vegetative phase, which can be attributed to the lower temperature rather than reduced mean daily radiation. Summary statistics suggested that there was ample opportunity to improve rice yield in early season crops, compared with late season crops. Correlation analysis further showed that spikelets per m², panicles per m², leaf area index at panicle initiation and flowering, biomass at physiological maturity and biomass accumulation after flowering should be emphasized for increasing grain yield, especially in early season crops under the double rice-cropping system in central China. Current breeding programs need to target strong tillering ability, large panicle size and greater grain filling (%) for early season crops, and high yield potential and lodging-resistance for late season crops as primary objectives.     

The components of lucerne (Medicago sativa) leaf area index respond to temperature and photoperiod in a temperate environment

Irrigated crops of ‘Grasslands Kaituna’ lucerne were grown for 5 years in a temperate climate at Lincoln University, Canterbury, New Zealand (43°38′S, 172°28′E). From these the response of the components of leaf area index (LAI) to environmental factors was determined. A broken stick temperature threshold with a base temperature (T_b) of 1 °C at air temperatures (T_a) <15 °C and a T_b = 5 °C for T_a ≥ 15 was required to accumulate thermal time (Tt). Using this, the appearance of nodes on the main-stem (phyllochron) was constant in Tt within a re-growth cycle (30–42 days). The phyllochron was 37 ± 7 °Cd but declined from 60 to 37 °Cd as photoperiod decreased from 15.7 to 11.4 h. Branching began at the appearance of the fifth main-stem node with 2.5 secondary nodes produced per main-stem node in spring re-growth cycles but only 1.7 produced in summer. Leaf senescence increased from 0.3 to 1.08 leaves per main-stem node after the appearance of the ninth node. Spring re-growth cycles had a mean individual leaf area of 170 mm² compared with 400 mm² for summer re-growth cycles. These results demonstrate systematic variation in LAI components and suggest they need to be considered separately in response to environmental factors to provide a quantitative framework for crop simulation analyses of lucerne canopy development.     

Optimising crop production and nitrate leaching in China: Measured and simulated effects of straw incorporation and nitrogen fertilisation

The sustainability of growing a maize—winter wheat double crop rotation in the North China Plain (NCP) has been questioned due to its high nitrogen (N) fertiliser use and low N use efficiency. This paper presents field data and evaluation and application of the soil–vegetation–atmosphere transfer model Daisy for estimating crop production and nitrate leaching from silty loam fields in the NCP. The main objectives were to: i) calibrate and validate Daisy for the NCP pedo-climate and field management conditions, and ii) use the calibrated model and the field data in a multi-response analyses to optimise the N fertiliser rate for maize and winter wheat under different field managements including straw incorporation.The model sensitivity analysis indicated that a few measurable crop parameters impact the simulated yield, while most of the studied topsoil parameters affect the simulated nitrate leaching. The model evaluation was overall satisfactory, with root mean squared residuals (RMSR) for simulated aboveground biomass and nitrogen content at harvest, monthly evapotranspiration, annual drainage and nitrate leaching out of the root zone of, respectively, 0.9 Mg ha⁻¹, 20 kg N ha⁻¹, 30 mm, 10 mm and 10 kg N ha⁻¹ for the calibration, and 1.2 Mg ha⁻¹, 26 kg N ha⁻¹, 38 mm, 14 mm and 17 kg N ha⁻¹ for the validation. The values of mean absolute deviation, model efficiency and determination coefficient were also overall satisfactory, except for soil water dynamics, where the model was often found erratic. Re-validation run showed that the calibrated Daisy model was able to simulate long-term dynamics of crop grain yield and topsoil carbon content in a silty loam field in the NCP well, with respective RMSR of 1.7 and 1.6 Mg ha⁻¹. The analyses of the model and the field results showed that quadratic, Mitscherlich and linear-plateau statistical models may estimate different economic optimal N rates, underlining the importance of model choice for response analyses to avoid excess use of N fertiliser. The analyses further showed that an annual fertiliser rate of about 300 kg N ha⁻¹ (100 for maize and 200 for wheat) for the double crop rotation with straw incorporation is the most optimal in balancing crop production and nitrate leaching under the studied conditions, given the soil replenishment with N from straw mineralisation, atmospheric deposition and residual fertiliser.This work provides a sound reference for determining N fertiliser rates that are agro-environmentally optimal for similar and other cropping systems and regions in China and extends the application of the Daisy model to the analyses of complex agro-ecosystems and management practices under semi-arid climate.     

Evaluating the accuracy of VEMAP daily weather data for application in crop simulations on a regional scale

Weather plays a critical role in eco-environmental and agricultural systems. Limited availability of meteorological records often constrains the applications of simulation models and related decision support tools. The Vegetation/Ecosystem Modeling and Analysis Project (VEMAP) provides daily weather variables on a 0.5 latitude–longitude grid across the conterminous USA. Daily weather data from the VEMAP (1961–1990) for the state of Georgia were compared with data from 52 individual ground stations of the National Weather Service Cooperative Observer Program (COOP). Additionally, simulated crop grain yields of soybean (Glycine max) were compared using the two data sources. Averaged daily maximum and minimum temperatures (Tmax and Tmin, respectively), solar radiation (SRAD), and precipitation (PPT) differed by 0.2 °C, ?0.2 °C, 1.7 MJ m^?2 d^?1, and 0 mm, respectively. Mean absolute errors (MAEs) for Tmax, Tmin, SRAD, and PPT were 4.2 °C, 4.4 °C, 4.4 MJ m^?2 d^?1, and 6.1 mm, respectively, and root mean squared errors (RMSEs) for Tmax, Tmin, SRAD, and PPT were 5.5 °C, 5.9 °C, 5.8 MJ m^?2 d^?1, and 13.6 mm, respectively. Temperature differences were lowest during summer months. Simulations of grain yield using the two data sources were strongly correlated (r = 0.68, p < 0.01). The MAE of grain yield was 552 kg ha^?1. The RMSE of grain yield was 714 kg ha^?1. Hybrid analyses indicated that the variation of simulated yield was mainly associated with the differences in rainfall. The results showed that the VEMAP daily weather data were able to be adequately applied to crop growth simulation at spatial and temporal scales, especially for long-term climate change research. Overall, the VEMAP weather data appears to be a promising source for crop growth modeling concerned with scale to 0.5° coordinate grid.     

Development of critical nitrogen dilution curve in rice based on leaf dry matter

The critical nitrogen (N_c), defined as the minimum N concentration required for maximum growth, is proposed for diagnosis of the in-season N status in crop plants. It has been established for several crops including rice on whole-plant dry matter (DM) basis but has not been determined for canopy leaf basis. This research was undertaken to develop a new N_c dilution curve based on leaf dry matter (L_DM) and to assess its applicability to estimate the level of N nutrition for Japonica rice in east China. Three field experiments were conducted with varied N rates (0–360 kg N ha⁻¹) and three Japonica rice (Oryza sativa L.) hybrids, Lingxiangyou-18 (LXY-18), Wuxiangjing-14 (WXJ-14) and Wuyunjing (WYJ) in Jiangsu province of east China. Five hills from each plot were sampled from active tillering to heading for growth analysis and leaf N determination. The N_c dilution curve on leaf N concentration was described by the equation N_c = 3.76W^−0.218, when L_DM ranged from 0.67 to 4.25 t ha⁻¹. However, for L_DM < 0.67 t ha⁻¹, the constant critical value N_c = 4.09%L_DM was applied. This N_c dilution curve on L_DM basis was slightly higher than the curves on plant DM basis in Japonica rice, yet both lower than the reference curve of high yielding Indica rice in tropics. The N nutrition index (NNI) and accumulated N deficit (N_and) of leaves ranged from 0.65 to 1.06 and 79.62 to −6.39 kg ha⁻¹, respectively, during main growth stages under varied N rates in 2010 and 2011. The results indicate that the present N_c dilution curve and derived NNI and N_and adequately identified the situations of N-limiting and non-N-limiting nutrition in two rice varieties and could be used as reliable indicators of N status during growth of Japonica rice in east China.     

Crop and cattle production responses to tillage and cover crop management in an integrated crop–livestock system in the southeastern USA

Integrated crop–livestock systems can help achieve greater environmental quality from disparate crop and livestock systems by recycling nutrients and taking advantage of synergies between systems. We investigated crop and animal production responses in integrated crop–livestock systems with two types of winter cover cropping (legume-derived N and inorganic fertilizer N), two types of tillage [conventional disk (CT) and no tillage (NT)], and whether cover crops were grazed by cow/calf pairs or not. The 13-ha field study was a modification of a previous factorial experiment with four replications on Ultisols in Georgia, USA. Recurring summer drought severely limited corn and soybean production during all three years. Type of cover crop had little influence and grazing of cover crops had minor influence on crop production characteristics. Cattle gain from grazing of winter cover crops added a stable component to production. No-tillage management had large positive effects on corn grain (95 vs. 252 g m⁻² under CT and NT, respectively) and stover (305 vs. 385 g m⁻²) production, as well as on soybean grain (147 vs. 219 g m⁻²) and stover (253 vs. 375 g m⁻²) production, but little overall effect on winter wheat grain (292 g m⁻²) and stover (401 g m⁻²) production. Our results suggest that robust, diversified crop–livestock systems can be developed for impoverished soils of the southeastern USA, especially when managed under no tillage to control environmental quality and improve resistance of crops to drought.     

Is it possible to forecast the grain quality and yield of different varieties of winter wheat from Minolta SPAD meter measurements?

To optimize wheat segregation for the various markets, it is necessary to add to genotype segregation, a prediction before harvest of the values of yield and grain protein concentration (GPC) for the different fields of the collecting area. Different tools allowing a prediction of crop production exist. Among them, the evaluation of nitrogen concentration by a chlorophyll meter (Soil–Plant Analysis Development (SPAD) readings), classically used to adapt the nitrogen fertilizer application, has been used in few works to foresee grain yield and grain protein concentration. But the relationships between N crop status and SPAD measurements varies among varieties and this genotypic effect has rarely been incorporated in models of forecasting grain quality.This paper compares several models to forecast yield, nitrogen uptake in grain (NUG) and grain protein concentration from trials carried out in 2001 and 2002 at the INRA experiment station of Grignon (West of Paris). Trials crossed nine varieties by four (2002) or five (2001) nitrogen rates. Input variables of those models are mainly chlorophyll meter measurements (SPAD) on the penultimate leaf at GS65 and on the flag leaf at GS71 Zadoks growth stages and ear number per square meter (NE).A square root model of yield based on NE × SPAD gave the best fit (RMSE = 0.6 t ha⁻¹ for both stages) if considering three different groups of genotypes. Based on the same variable, NE × SPAD, a quadratic model for NUG without significant effect of genotypes gave the best fit (RMSE, between 21 and 30 kg ha⁻¹ depending of the growth stage). And, for GPC, considering the same three groups of genotypes, the slope of the linear model with the ratio of predicted grain nitrogen concentration to predicted yield, is the same at both stages and very close to the standard value used to calculate protein concentration from nitrogen concentration (5.7), but the predictive quality of the model is more than 10% higher at GS71 (R² of 0.77) than at flowering (R² of 0.64). Finally, the sensibility of the models to delay in the stage of measurement is discussed.     

Cereal yield and quality as affected by nitrogen availability in organic and conventional arable crop rotations: A combined modeling and experimental approach

The effects of nitrogen (N) availability related to fertilizer type, catch crop management, and rotation composition on cereal yield and grain N were investigated in four organic and one conventional cropping systems in Denmark using the FASSET model. The four-year rotation studied was: spring barley–(faba bean or grass-clover)–potato–winter wheat. Experiments were done at three locations representative of the different soil types and climatic conditions in Denmark. The three organic systems that included faba bean as the N fixing crop comprised a system with manure (stored pig slurry) and undersowing catch crops (OF + C + M), a system with manure but without undersowing catch crops (OF ? C + M), and a system without manure and with catch crops (OF + C ? M). A grass-clover green manure was used as N fixing crop in the other organic system with catch crops (OG + C + M). Cuttings of grass-clover were removed from the plots and an equivalent amount of total-N in pig slurry was applied to the cropping system. The conventional rotation included mineral fertilizer and catch crops (CF + C + F), although only non-legume catch crops were used. Measurements of cereal dry matter (DM) at harvest and of grain N contents were done in all plots. On average the FASSET model was able to predict the yield and grain N of cereals with a reasonable accuracy for the range of cropping systems and soil types studied, having a particularly good performance on winter wheat. Cereal yields were better on the more loamy soil. DM yield and grain N content were mainly influenced by the type and amount of fertilizer-N at all three locations. Although a catch crop benefit in terms of yield and grain N was observed in most of the cases, a limited N availability affected the cereal production in the four organic systems. Scenario analyses conducted with the FASSET model indicated the possibility of increasing N fertilization without significantly affecting N leaching if there is an adequate catch crop management. This would also improve yields of cereal production of organic farming in Denmark.     

Crop yields under no-till farming in China: A meta-analysis

No-till (NT) farming is popular globally, however, the effects on crop yields remain debatable. A meta-analysis was conducted on crop yield responses to NT in China based on 1006 comparisons from 164 studies. Results showed that a decrease of 2.1 ± 1.8% on crop yield was observed under NT with residue removed (NT0) compared with that under plow tillage with residue removed (PT0), but the decreases can be diminished to 1.9 ± 1.0% when residue retention was combined with both the two tillage practices. On the contrary, NT with residue retention (NTR) may significantly increase crop yields by 4.6 ± 1.3% compared with that under PT0 (P < 0.05). Along with improvements in crop yields, increases in soil organic carbon (SOC) by 10.2 ± 7.2%, available nitrogen (N) by 9.4 ± 5.4%, available potassium by 10.5 ± 8.8%, and water storage by ∼9.3 ± 2.4% was observed under NTR compared with PT0, indicating that improvements in soil quality could benefit crop productivity under NTR. Categorically, results on meta-analysis and regression indicated large variations in crop yields under NTR because of differences in crop species, temperature and precipitation, antecedent SOC level, N fertilizer input, duration of adoption, and with or without residue retention. For example, crop yields significantly increased with increase in duration (P < 0.0001) under NTR, by 21.3% after 10 years of continuous NTR compared with PT0. Adoption of NTR under appropriate site-specific conditions can advance China’s food security, improve yield stability and alleviate soil-related constraints.     

Water content dynamics of achene,pericarp and embryo in sunflower: Associations with achene potential size and dry-down

The post-anthesis dynamics of the water content of whole sunflower achene and its major parts (pericarp, embryo) were examined for seven genotypes that spanned a broad range of final achene size (30–100 mg achene^?1). Objectives were: (i) to establish the relative contributions of pericarp and embryo to whole-achene water content dynamics, (ii) to determine the relationship between maximum water content of the pericarp and final achene size, and (iii) to examine the effect of final achene size (as affected by genotype and environment) on achene dry-down dynamics after physiological maturity (=maximum achene weight). Four experiments were conducted over 2 years under field and glasshouse conditions. Across genotypes and growth conditions, whole-achene and pericarp water contents peaked earlier and more sharply during grain filling (ca. 35% of grain filling duration, or 30% of final achene weight), maximum embryo water content was achieved somewhat later and declined less sharply. Although the pericarp was a minor (17–35%) component of final achene dry weight, it contained 65–70% of achene maximum water content. Absolute pericarp water content did not fall to values close to those of the embryo until after physiological maturity. Final achene and embryo dry weights were closely (r² 0.90 and 0.85, respectively) associated with maximum pericarp water content. After maximum achene water content, rates of whole-achene dry-down were linear (ca. 1.35% d^?1), and absolute rates of water loss per achene (range = 1.1–3.7 mg H₂O achene^?1 d^?1) were strongly associated with achene maximum water content and final achene dry weight (r² 0.86 and 0.75, respectively). Excluding the inbred line HA89, the remaining genotypes achieved harvest (17%) and storage (11%) achene water concentrations at about 15 and 20 d, respectively, after physiological maturity, largely because absolute rates of achene water loss increased with achene size. We conclude that the pericarp is the dominant component of whole-achene water content dynamics, and that pericarp and achene maximum water contents are good indicators of potential final achene and embryo sizes and achene dry-down rates. Present results also provide a first approximation to the quantification of post-physiological maturity dry-down in this crop.     

No-tillage permanent bed planting and controlled traffic in a maize-cotton irrigated system under Mediterranean conditions: Effects on soil compaction,crop performance and carbon sequestration

Under irrigated Mediterranean conditions, no-tillage permanent bed planting (PB) is a promising agriculture system for improving soil protection and for soil carbon sequestration. However, soil compaction may increase with time up to levels that reduce crop yield. The aim of this study was to evaluate the mid-term effects of PB on soil compaction, root growth, crop yield and carbon sequestration compared with conventionally tilled bed planting (CB) and with a variant of PB that had partial subsoiling (DPB) in a Typic Xerofluvents soil (Soil Survey Staff, 2010) in southern Spain. Traffic was controlled during the whole study and beds, and furrows with (F + T) and without traffic (F − T), were spatially distinguished during measurements. Comparisons were made during a crop sequence of maize (Zea mays L.)—cotton (Gossypium hirsutum L.)—maize, corresponding to years 4–6 since trial establishment. After six years, soil compaction was higher in PB than in CB, particularly under the bed (44 and 27% higher in top 0.3- and 0.6-m soil layers, respectively). Around this time, maize root density at early grain filling was 17% lower in PB than in CB in the top 0.6-m layer. In DPB, the subsoiling operation was not effective in increasing root density. Nevertheless, root density appeared to maintain above-ground growth and yield in both PB and DPB compared to CB. Furthermore, at the end of the study, more soil organic carbon was stocked in PB than in CB and the difference increased significantly with a depth down to 0.5 m (5.7 Mg ha⁻¹ increment for the top 0.5-m soil layer). Residues tended to accumulate on furrows, and this resulted in spatial and temporal differences in superficial soil organic carbon concentration (SOC) in the permanent planting systems. In PB, SOC in the top 0.05-m layer increased with time faster in furrows than on beds, and reached higher stable values (1.67 vs. 1.09% values, respectively). In CB, tillage homogenized the soil and reduced SOC in the top 0.05-m layer (average stable value of 0.96% on average for beds and furrows).