The “Felina 32” variety of industrial hemp (Cannabis sativa L.) is among the most popular cultivated varieties in Lithuania. In 2020 to 2021, the height of the above-ground portion of “Felina 32” ...ranged from about 1.37 to 2.52 m. In the less favorable year of 2021, 9.8% lower height and 28.5% lower mass plants grew. However, the impact of meteorological conditions on their comparative indicators was not confirmed. Two critical intervals were distinguished, which essentially influence the dynamics of plant growth: crop density of 90 to 150 plants∙m2 and plant height of 1.9 m to 1.99 m. Lower crop density results in larger plants, and plants taller than 1.9 m gain mass 2.58 times faster than shorter plants. In addition, industrial hemp of different heights is characterized by differences in the development of morphological parts. This directly affects the physical and chemical properties of biomass. It was determined that when the height of “Felina 32” variety changes, the heat value of biomass increases 0.342 MJ/kg, carbon concentration increases 0.70%, and ash content, sulfur, nitrogen, and chlorine concentrations decreased.
The question of how to meet rising food demand at the least cost to biodiversity requires the evaluation of two contrasting alternatives: land sharing, which integrates both objectives on the same ...land; and land sparing, in which high-yield farming is combined with protecting natural habitats from conversion to agriculture. To test these alternatives, we compared crop yields and densities of bird and tree species across gradients of agricultural intensity in southwest Ghana and northern India. More species were negatively affected by agriculture than benefited from it, particularly among species with small global ranges. For both taxa in both countries, land sparing is a more promising strategy for minimizing negative impacts of food production, at both current and anticipated future levels of production.
Crop height and density estimation ahead of the combine harvester have been investigated over the last 30 years, but they remain a challenge. LiDAR technology is increasingly being investigated for ...phenotyping and monitoring of cereals. However, so far, little has been published about the influence of laser mounting position and robust online measurement of height and density from a single LiDAR scan. Therefore, the influence of the angle and height of the LiDAR mounting on crop height and density estimation in wheat and barley was investigated in this study. Tests were conducted in different crop heights, densities, moisture levels and varieties. The crop height was estimated with a root mean squared error of 0.082 m at an angle of 90° between the LiDAR scanning plane and the horizontal. Two methods were compared for crop density estimation. The inter-percentile and the transversal variance method both successfully predicted the crop density, but the variance based method performed better with a coefficient of determination (R2) of 0.77 and a root mean squared error of 82 g dry ears m-2. When considering only one variety, the performance improved to reach an R2 of 0.8 and a root mean squared error of 44 g dry ears m-2. Variation in mounting angle of the sensor had less effect on the prediction accuracy than the mounting height.
•LiDAR allows to estimate crop height and density in small grain crop.•Crop height cannot be estimated properly at angles to the horizontal below 70°.•Variance based crop density estimation is robust against small viewing angle variations.•LiDAR data correlate better to ears dry mass than to number of tillers.
Long-term ecological effects of transgenic Bacillus thuringiensis (Bt) crops on nontarget pests have received limited attention, more so in diverse small holder-based cropping systems of the ...developing world. Field trials conducted over 10 years in northern China show that mirid bugs (Heteroptera: Miridae) have progressively increased population sizes and acquired pest status in cotton and multiple other crops, in association with a regional increase in Bt cotton adoption. More specifically, our analyses show that Bt cotton has become a source of mirid bugs and that their population increases are related to drops in insecticide use in this crop. Hence, alterations of pest management regimes in Bt cotton could be responsible for the appearance and subsequent spread of nontarget pests at an agro-landscape level.
Summary One-year experiments conducted with one hemp variety were established to determinate the cultivation practices (growth density and pinching) which could be used to optimize the technological ...process of hemp varieties production for different purposes. The results showed that reduced crop density and pinching result in development of shorter plants. In denser non-pinched crops, the stem is over 180 cm high, while the plants start branching in the upper 1/4-1/5 part. In the non-pinched treatment with a larger area available for individual plants, as well as in the pinched treatments, more productive branches of less thickness develop in the lower parts. The non-pinched treatments generally produce higher stem and fiber yields, which increase when crop density is reduced. The obtained results can serve as a basis for determining certain treatments during the evaluation of production technology for different varieties of hemp intended for specific purposes.
Ecological intensification aims to reduce environmental costs of agricultural production by increasing biodiversity and using the associated ecosystem services instead of, or in combination with, ...external inputs, so that yields are maintained at high levels or increased. However, to date there are few measures available for which such benefits have already been demonstrated in the field.
In this study, the seeding pattern in winter wheat fields was manipulated to create a diversified crop architecture consisting of ‘unsown-rows’ and ‘densely-sown-rows’ in treatment fields in comparison to ‘conventionally-sown-rows’ in control fields to assess whether (i) in-field structural and microclimatic conditions are more heterogeneous in fields with manipulated crop architecture compared to conventionally managed fields, (ii) a change in crop architecture is related to higher species richness, activity density and altered body size distribution of carabid communities, (iii) this in turn increases natural pest and weed seed control, but (iv) does not lead to yield loss.
In-field structural and microclimatic conditions were more heterogeneous in treatment fields compared to control fields, which was associated with significantly increased body sizes of predatory carabids and a trend for increased predatory carabid species richness (in the ‘unsown-rows’ of treatment fields). These changes were related to significantly stronger pest suppression in the ‘densely-sown-rows’ of treatment fields compared to ‘conventionally-sown-rows’ in control fields, with 10 % higher experimental pest predation rates and 56 % reduced crop damage caused by cereal leaf beetles. Moreover, carabids known to consume weed seeds showed significantly higher activity densities in ‘unsown-rows’ compared to ‘conventionally-sown-rows’, which was related to significantly higher experimental weed seed predation in ‘densely-sown-rows’. Wheat yields were not significantly different in fields with or without manipulated crop architecture.
The results suggest that the simple measure of manipulating the seeding pattern in winter wheat fields creates a diversified crop architecture, thereby promoting carabid diversity and altering their community composition and activity density such that important ecosystem services are increased without yield losses. Thus, beyond fostering biodiversity, this measure has, although not directly tested here, the potential for being used for ecological replacement of pesticides through enhanced ecosystem services without entailing agronomic and economic disadvantages such as land opportunity costs or increased workload.
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•Manipulating crop architecture as new in-field measure for ecological intensification.•Easy applicability by simply closing some sowing coulters without reducing seed quantity.•Higher habitat heterogeneity in manipulated fields with different crop densities.•Changes in carabid communities were positively related to pest control services.•Potential to save pesticides without reducing wheat yield.
Appropriate genotype selection and management can impact wheat (
L.) yield in dryland environments, but their impact on yield components and their role in yield modulation are not well understood. ...Our objectives were to evaluate the yield response of commercial winter wheat genotypes to different management practices reflecting a stepwise increase in management intensity (including a reduction in crop density under high input), and to quantify how the different yield components modulate wheat yield. A factorial experiment evaluated six management (M) intensities "farmer practice" (FP), "enhanced fertility" (EF), "ecological intensification" (EI), "increased foliar protection" (IFP), "water-limited yield" (Yw), and "increased plant productivity" (IPP) and four winter wheat genotypes (G) in four Kansas environments (E). Average grain yield was 4.9 Mg ha
and ranged from 2.0 to 7.4 Mg ha
, with significant two-way interactions (E × M and E × G). The EF usually maximized yields in dry environments, while EI, which consisted of EF plus one fungicide application, maximized yields in environments with greater water availability. Across all sources of variation, kernels m
and aboveground biomass were the strongest modulators of yield as compared to kernel weight and harvest index, while spikes m
and kernels spike
modulated yields at a similar magnitude. Foliar fungicides improved yield through increased green canopy cover duration and greater radiation intercepted during grain filling. When crop density was reduced from 2.7 to 1.1 million plants per hectare in an otherwise high-input system, plants produced more productive tillers (with genotype-specific response); however, reduced green canopy cover at anthesis and reduced cumulative solar radiation intercepted during grain filling limited wheat yield-although large differences in canopy cover or intercepted radiation were needed to cause modest changes in yield. Treatments more intensive than EI were not warranted as EF or EI maximized yields at all environments, and practices that promote biomass and kernels m
are to be targeted for future increases in wheat yield.
URBANIZATION AND STRUCTURAL TRANSFORMATION Michaels, Guy; Rauch, Ferdinand; Redding, Stephen J.
The Quarterly journal of economics,
05/2012, Volume:
127, Issue:
2
Journal Article
Peer reviewed
Open access
We examine urbanization using new data that allow us to track the evolution of population in rural and urban areas in the United States from 1880 to 2000. We find a positive correlation between ...initial population density and subsequent population growth for intermediate densities, which increases the dispersion of the population density distribution over time. We use theory and empirical evidence to show this pattern of population growth is the result of differences in agriculture's initial share of employment across population densities, combined with structural transformation that shifts employment away from agriculture.
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