Sorghum aphid, Melanaphis sorghi (Theobald) have become a major economic pest in sorghum causing 70% yield loss without timely insecticide applications. The overarching goal is to develop a ...monitoring system for sorghum aphids using remote sensing technologies to detect changes in plant-aphid density interactions, thereby reducing scouting time. We studied the effect of aphid density on sorghum spectral responses near the feeding site and on distal leaves from infestation and quantified potential systemic effects to determine if aphid feeding can be detected. A leaf spectrometer at 400–1000 nm range was used to measure reflectance changes by varying levels of sorghum aphid density on lower leaves and those distant to the caged infestation. Our study results demonstrate that sorghum aphid infestation can be determined by changes in reflected light, especially between the green–red range (550–650 nm), and sorghum plants respond systemically. This study serves as an essential first step in developing more effective pest monitoring systems for sorghum aphids, as leaf reflection sensors can be used to identify aphid feeding regardless of infestation location on the plant. Future research should address whether such reflectance signatures can be detected autonomously using small unmanned aircraft systems or sUAS equipped with comparable sensor technologies.
Food equivalent unit (FEU) is a vector used to measure the value of food based on its calorie and protein content and their digestibility. However, the optimal planting density and N application rate ...for maximizing the FEU yield (FEUY) of forage maize (Zea mays L.) is still poorly understood in the fast-growing animal husbandry regions of the Chinese Loess Plateau. Here, a 2-year consecutive field experiment was conducted to explore the impacts of planting density, N application rate, and their interactions on growth, dry matter yield (DMY), forage quality, and FEUY of a dominant forage maize cultivar. Planting density significantly affected the stem diameter, LAI, DMY, and dry matter allocation (DMA) of the leaf. Initially, increasing the N rate increased the stem diameter, LAI, FEUY, and DMY of forage maize and then decreased. The stem diameter, LAI, FEUY and above-ground DMY peaked under 180 kg∙ha−1 N in both years. Moreover, N application significantly increased the crude protein content of the whole plant and decreased the acid detergent fiber content. The surface fittings of the 2-year study indicated that 110,000 plants∙ha−1 (plant density) and 171.2 kg∙ha−1 (N rate) obtained the greatest DMY (19.0 t∙ha−1). The grade index (a comprehensive evaluation index for forage quality) peaked at 15.4 MJ∙d−1 under 94,000 plants ha−1 and 270 kg∙ha−1. The 110,000 plants∙ha−1 plant density and 181.5 kg∙ha−1 N rate jointly maximized the FEUY (11,125.4 FEU∙ha−1), maintaining 99.9 % of the maximum DMY and 97.5 % of the maximum grade index. Thus, 110,000 plants∙ha−1 plant density and 181.5 kg∙ha−1 N rate are recommended for high-productivity forage maize production, without notably compromising dry matter yield and feed quality. This research is conducive to advancing the coordinated development of forage crop cultivation and herbivorous livestock farming in semi-arid rainfed areas.
•The effect of N rates on grade index of forage maize is greater than that of planting density.•Density 110,000 plants∙ha−1 and N rate 181.5 kg∙ha−1 maximized food equivalent unit yield.•The optimal maintained 99.9 % of the yield and 97.5 % maximum grading index.
Background. Taro (Colocasia esculenta) can be grown in a variety of environmental and edaphic conditions, but it is most typically grown in wetlands. The optimal conditions for its growth are two ...water regimes i.e., waterlogged or flooded conditions to dryland or unflooded conditions. An important criterion in crop yield is water use efficiency (WUE), and it has been suggested that crop production per unit of water used can be increased. Objectives. To determine the WUE of taro in Kenya’s sub-humid environment under different watering regimes and planting densities. Methodology. A study was conducted at the Kenya Agricultural and Livestock Research Organization (KALRO) – Embu Research Centre, during the long rains (LR) 2021, short rains (SR) 2021/2022, and long rains (LR) 2022. A factorial experiment with a split-plot layout arranged in a completely randomized block design was used. The main factor was the irrigation levels while the sub-factor was the planting density, with three replications. The three irrigation levels were at 100 %, 60 %, and 30 % based on the field capacity (FC). The planting densities used were 0.5m × 0.5m (40,000 plants ha-1), 1m × 0.5m (20,000 plants ha-1), and 1m × 1m (10,000 plants ha-1), representative of high, medium, and low planting densities respectively. Results. The WUE was influenced by season and watering regime (P < 0.05). The 30% FC had the highest WUE with the 100 % FC having the lowest. The high WUE under 30 % FC (19.40 kg ha-1mm-1) was associated with the high biomass (1.97 kg) and low water use (2269.41 mm) recorded under limited water conditions. The medium (1m × 0.5m) planting density attained the highest WUE (12.16 kg ha-1mm-1) with the high planting density (0.5m × 0.5m) having the lowest (10.65 kg ha-1mm-1), though no significant differences were recorded. Implications. The varying watering regimes and planting densities in this study have different capacities to utilize the supplied water. The total taro biomass increased with decrease in water supplied and in turn maximized the water use efficiency. Conclusion. To achieve the highest yield per unit of water consumed, a watering regime of 30 % FC and a planting density of 1 m × 0.5 m (20,000 plants ha-1) is recommended.
The oil palm yield depends on its genetic and the interaction with environmental factors is affected by spatial arrangement of palm trees. The research objectives are to determine the effect of ...population density and planting year on oil palm productivity and vegetative growth. This research uses a factorial design arranged with a randomized complete design. Secondary data are palm productivity, fresh bunch number and bunch weight that were collected for three years (2019—2022). Primary data are stem height, frond length, and stem gird which were measured on 90 trees for each treatment combination. There are nine combinations with 810 palm trees that were sampled from 27 estate blocks (30 hectares for one block). The results showed that productivity and amount of oil palm FFB at densities ≥ 142, 136-141, and ≤ 135 SPH and planting years 2007, 2009 and 2011 (mature crop 12-15, 10-13, and 8-11 years) did not show significant differences. The heavier bunch weight was produced palm tree planted in 2007 with density ± 135 trees.ha-1.
Matching of maize growth with solar radiation is of great importance for achieving high yield. We conducted experiments using different maize cultivars and planting densities under different solar ...radiations during grain filling to quantitatively analyze the relationships among these factors. We found that a decrease in solar radiation after silking caused a drop in maize grain yield and biomass, with lower solar radiation intensities leading to worse grain yields and biomass. Cultivar ZD958 was more sensitive to solar radiation changes than cultivar XY335; slight decreases in solar radiation (i.e., 15% shading) caused significant declines in ZD958 grain yield. When total solar radiation during grain filling was less than 486.9 MJ m
for XY335 and less than 510.9 MJ m
for ZD958, the two cultivars demonstrated high yields at lower planting density of 7.5 × 10
plants ha
; average yields were 13.36 and 11.09 Mg ha
, respectively. When radiation intensities were higher than 549.5 MJ m
for XY335 and higher than 605.8 MJ m
for ZD958, yields were higher at a higher planting density of 12 × 10
plants ha
, with average yields of 20.58 Mg ha
for XY335 and 19.65 Mg ha
for ZD958.
The exploitative segregation of plant roots Cabal, Ciro; Martínez-García, Ricardo; de Castro Aguilar, Aurora ...
Science (American Association for the Advancement of Science),
12/2020, Letnik:
370, Številka:
6521
Journal Article
Recenzirano
Plant roots determine carbon uptake, survivorship, and agricultural yield and represent a large proportion of the world's vegetation carbon pool. Study of belowground competition, unlike aboveground ...shoot competition, is hampered by our inability to observe roots. We developed a consumer-resource model based in game theory that predicts the root density spatial distribution of individual plants and tested the model predictions in a greenhouse experiment. Plants in the experiment reacted to neighbors as predicted by the model's evolutionary stable equilibrium, by both overinvesting in nearby roots and reducing their root foraging range. We thereby provide a theoretical foundation for belowground allocation of carbon by vegetation that reconciles seemingly contradictory experimental results such as root segregation and the tragedy of the commons in plant roots.
Optimal plant density and nitrogen (N) application rate are important to achieve high maize yield. High plant density increases plant-plant competition for light and nutrients. However, too much ...applied N promotes excessive vegetative growth and delays maturity, resulting in low N use efficiency (NUE) and potentially environmental problems. The physiological and molecular mechanisms behind the interaction between plant density and N application rate are largely unknown.
We hypothesized that simultaneously improving maize yield and NUE depends on fine regulation of nitrogen partitioning in response to the interaction between nitrogen applications and plant densities.
With a 2-year field experiment, we performed phenotypic, physiological, and gene expression analyses under two plant densities (low density of 60,000 plants ha-1 and high density of 90,000 plants ha-1) and three nitrogen application levels 115 (N1), 190 (N3) and 430 (N4) kg N ha-1 in the high N-responsiveness maize cultivar ZD958.
By labeling maize with 15N, 2-year results showed that both 15N uptake per plant and 15N partitioning to ear decreased under high-density conditions. Compared to N1 treatment, application of N to N3/N4 level increased maize yield by 13.9%− 43.2%, which can be explained by bigger root angle, larger leaf area and lower lodging rate under high density condition. In addition, results in 2019 experiment showed that yield, NUE, nitrogen allocation to stem and the expression of some N transporter genes were regulated by the interaction between nitrogen applications and plant densities. Compared to the N4 treatment, N3 treatment has a 55.8% reduction in N, a tendency of increase in population yield, and increased NUE by 59.6% and 63.0% in low-density and high-density plantings, respectively. Our proposed model suggested that the appropriate N supply increased NUE by either increasing N translocation from leaves to ears under low-density conditions or by increasing N allocation to ears rather than to stems under high-density conditions.
Based on correlation analysis, N allocation/translocation and expression of nitrogen transporter genes could be used as biomarkers to indicate appropriate levels of N application under different planting densities, and are thereby important for the simultaneously improving ZD958 yield and NUE in intensive agriculture.
Much of humanity relies on rice (Oryza sativa) as a food source, but cultivation is water intensive and the crop is vulnerable to drought and high temperatures. Under climate change, periods of ...reduced water availability and high temperature are expected to become more frequent, leading to detrimental effects on rice yields.
We engineered the high-yielding rice cultivar ‘IR64’ to produce fewer stomata by manipulating the level of a developmental signal. We overexpressed the rice epidermal patterning factor OsEPF1, creating plants with substantially reduced stomatal density and correspondingly low stomatal conductance.
Low stomatal density rice lines were more able to conserve water, using c. 60% of the normal amount between weeks 4 and 5 post germination. When grown at elevated atmospheric CO2, rice plants with low stomatal density were able to maintain their stomatal conductance and survive drought and high temperature (40°C) for longer than control plants. Low stomatal density rice gave equivalent or even improved yields, despite a reduced rate of photosynthesis in some conditions.
Rice plants with fewer stomata are drought tolerant and more conservative in their water use, and they should perform better in the future when climate change is expected to threaten food security.
Intercropping technology is applied widely in crop cultivation to help remediate soil polluted with heavy metals. To investigate the feasibility and potential of intercropping hyperaccumulator plants ...with crops in cadmium (Cd)- and zinc (Zn)-contaminated soil, a pot experiment was conducted to examine plant growth and the contents of Cd and Zn in the soil following intercropping of wheat and Sedum plumbizincicola. Five treatments were examined: control (wheat monoculture: 36 seedlings per pot), and intercropping of wheat with different planting densities of S. plumbizincicola (3, 6, 9 and 15 seedlings per pot, respectively). Results showed a decrease in soil pH, and in soil and wheat contents of Cd and Zn with increasing planting density of S. plumbizincicola, while the removal rate of Cd and Zn increased. Meanwhile, excessive planting (15 seedlings per pot) inhibited wheat growth by 27.34% compared with the control, and overall, the optimal planting density was 9 seedlings per pot, resulting in effective remediation with only a moderate effect on wheat growth. These findings highlight the value of intercropping S. plumbizincicola with wheat as a means of improving remediation of soil contaminated with heavy metals (Cd and Zn).
•Intercropping of wheat and S. plumbizincicola decreased soil pH and soil Cd and Zn.•Removal of soil Cd and Zn increased with increasing density of S. plumbizincicola.•A proper planting density of S. plumbizincicola was 9 seedlings per pot.•Intercropping with S. plumbizincicola reduced heavy metal contamination.
Patterns, mechanisms, projections, and consequences of tree mortality and associated broad-scale forest die-off due to drought accompanied by warmer temperatures-"hotter drought", an emerging ...characteristic of the Anthropocene-are the focus of rapidly expanding literature. Despite recent observational, experimental, and modeling studies suggesting increased vulnerability of trees to hotter drought and associated pests and pathogens, substantial debate remains among research, management and policy-making communities regarding future tree mortality risks. We summarize key mortality-relevant findings, differentiating between those implying lesser versus greater levels of vulnerability. Evidence suggesting lesser vulnerability includes forest benefits of elevated CO
2
and increased water-use efficiency; observed and modeled increases in forest growth and canopy greening; widespread increases in woody-plant biomass, density, and extent; compensatory physiological, morphological, and genetic mechanisms; dampening ecological feedbacks; and potential mitigation by forest management. In contrast, recent studies document more rapid mortality under hotter drought due to negative tree physiological responses and accelerated biotic attacks. Additional evidence suggesting greater vulnerability includes rising background mortality rates; projected increases in drought frequency, intensity, and duration; limitations of vegetation models such as inadequately represented mortality processes; warming feedbacks from die-off; and wildfire synergies. Grouping these findings we identify ten contrasting perspectives that shape the vulnerability debate but have not been discussed collectively. We also present a set of global vulnerability drivers that are known with high confidence: (1) droughts eventually occur everywhere; (2) warming produces hotter droughts; (3) atmospheric moisture demand increases nonlinearly with temperature during drought; (4) mortality can occur faster in hotter drought, consistent with fundamental physiology; (5) shorter droughts occur more frequently than longer droughts and can become lethal under warming, increasing the frequency of lethal drought nonlinearly; and (6) mortality happens rapidly relative to growth intervals needed for forest recovery. These high-confidence drivers, in concert with research supporting greater vulnerability perspectives, support an overall viewpoint of greater forest vulnerability globally. We surmise that mortality vulnerability is being discounted in part due to difficulties in predicting threshold responses to extreme climate events. Given the profound ecological and societal implications of underestimating global vulnerability to hotter drought, we highlight urgent challenges for research, management, and policy-making communities.
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