Low Plant Density Research Articles

Influence of nitrogen level and plant density on growth parameters and economic efficiency of sunflower cultured in Thua Thien Hue province

Sunflower (Helianthus annuus) cultivation is gaining popularity among Vietnamese farmers. Two separate experiments were conducted from January to April 2018 in a randomized complete block design with three replicates. Four levels of each factor were included in the experiments: 0, 20, 40, and 60 kg/ha for nitrogen and 11, 13, 16, and 20 plants/m2 for the density. The nitrogen fertilizer (up to 60 kg/ha) substantially affects the leaf area, diameters of stem plant, receptacle and flower head, and cut flower vase life. Low plant density works well on plant height, leaf number, width and length at the flowering stage, with the largest head diameter (17.2 cm) at the 13 plants/m2 density. Based on the results of both growth ability and economic efficiency, we suggested applying N at 60 kg/ha and planting at 16 plants/m2 density for growing F1 cut sunflowers in Thua Thien Hue province.

Optimum Plant Density for Increased Groundnut Pod Yield and Economic Benefits in the Semi-Arid Tropics of West Africa

Groundnut is a very important crop in the West and Central Africa (WCA) region, accounting for almost 70% of Africa’s groundnut production in 2019. Despite its economic importance, the crop’s yield is still low. For a high yield and profitable economic returns, optimal plant density is a fundamental crop management practice. Plant density experiments were conducted at the ICRISAT-Mali research station between 2016 and 2021 over the main rainy and dry seasons to determine the optimum density for maximum groundnut yield and economic benefits. The treatments contained row spacing of 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm, and 100 cm, with intra-row spacing of 10 cm, 15 cm, and 20 cm. Results showed that when plant density was increased, dry pod yield, production value, and net economic benefit per hectare increased in a no moisture stress scenario. During the rainy season, the 40 cm × 10 cm spacing gave the highest dry pod yield (1693 kg), production value ($891.6), and net benefit ($403.5) per hectare. The highest dry pod yield (3703 kg), production value ($2173), and net benefit ($1510.2) per hectare were obtained from 30 cm × 10 cm spacing during the dry season. The number of pods per plant and 100 SW increased with lower plant densities. Therefore, it is recommended to increase plant density to at least 222,000 plants per hectare in the Sudan Savannah agroecology of WCA.

Low Plant Density Improves Fruit Quality without Affecting Yield of Cucumber in Different Cultivation Periods in Greenhouse

With the development of the economy, the demand for cucumber quality is quickly increasing. The aim of this study was to elucidate the role that plant density plays in leaf photosynthesis, shoot dry matter distribution, yield and quality of cucumber in different cultivation periods under greenhouse conditions. Experimental treatments based on three plant density treatments (2.25, 3.0 and 3.75 plants m−2) were conducted in turn during three growth and harvest periods in a year. The results showed that the changes in photosynthesis and weekly yield per unit area were different and dependent on the harvest time, which was mainly induced by temperature and radiation. Interestingly, we found that reducing plant density did not significantly affect the photosynthesis of leaves and did not decrease weekly yield per unit area and total yield. Low-density treatment had the highest weekly yield per plant and total yield per plant in the three harvest periods, the highest ratio of dry matter being allocated to fruits and the highest contents of soluble sugar, total phenols, flavonoid, soluble protein, vitamin C (Vc), chlorophyll and carotenoids in fruits. Moreover, a relatively low nitrite content was found in fruits following low-density treatment. The study indicated that low-density treatment was associated with a high quality of fruits without reducing the cucumber’s total annual yield under natural light in the greenhouse. Hence, our study suggests that properly reducing cucumber plant density to 2.25 plants m−2 could be a practicable approach for greenhouses in Shanghai, China.

Maize response to localized mineral or organic NP starter fertilization under different soil tillage methods

An early maize (Zea mays L.) sowing date plays a key role in increasing the grain yield, especially in a temperate climate. The adoption of reduced tillage techniques, such as strip tillage (ST), can decrease cultivation costs, compared to plowing (PLOW), but might also reduce the crop early development rate as a result of lower soil temperatures. Therefore, farmers often adopt starter fertilizations when sowing maize, in order to improve the early-season nutrient uptake, nutrient use efficiency and plant development. The aims of this study were to assess the effects of the adoption of ST, compared to PLOW, and a starter fertilization with deep-injected digestate (DIG) or sub-surface placed diammonium phosphate (DAP), compared to an unfertilized treatment (NT) on the early growth, grain yield and grain qualitative and sanitary traits of maize. Field experiments were carried out in NW Italy over the 2019 and 2020 growing seasons on two different soils. ST determined cooler soil conditions at both sites, compared to PLOW, thus resulting in lower NDVI values due to both slower plant development and lower final crop density. The starter fertilization with DAP recorded the best early vigor and canopy development, expressed as plant height in both sites and for both tillage techniques, while the DIG values were intermediate between the DAP and NT treatments. Although the effects on the early vigor of maize differed between the experimental sites, displaying more pronounced differences in the finer-textured soil, ST on average delayed the flowering (+2.2 days) and consequently delayed the moisture dry down process (+1.2% grain moisture content at harvest), compared to PLOW. The starter fertilization with DIG or DAP led to an earlier flowering, compared to NT (−2.6 and −4.6 days, respectively). The grain yield was not affected by the tillage system, as the plants in ST compensated for the lower plant density with an increased ear length (+1.5%). Instead, DIG and DAP recorded similar and higher grain yields (+1.8 and +1.6 Mg ha−1) than NT. DIG application led to a higher grain protein content and lower level of fumonisin contamination than the other treatments, while ST determined higher deoxynivalenol values than PLOW. The combination of ST and DIG as a starter fertilization can help maintain the production level and the grain quality, compared to conventional techniques that involve the use of mineral fertilizers and plowing, thereby leading to a higher sustainability of the maize cropping system.

Canopy management: the balance between lodging risk and nitrogen use for spring wheat production in the Canadian Prairies

Lodging risk in spring wheat has grown with the introduction of high-yielding cultivars that require high nitrogen (N) inputs to optimize grain yield and protein content. Canopy management (CM) strategies have been used to reduce lodging risk. However, the short growing season and unpredictable moisture supply may limit the use of these strategies in the Canadian Prairies. The objective of this study was to quantify the ability of agronomic practices to modify the early season crop canopy, and hence lodging risk, and to determine how these practices influence N use and final grain N yield. Split-plot field trials were established at four site-years (SYs) in Manitoba to evaluate CM strategies including three plant densities, a split N fertilizer application, and the application of chlormequat chloride (CCC) on canopy size (dry matter (DM) and height at anthesis), N uptake and remobilization, lodging and stalk strength, grain yield, protein, and grain N yield on the cultivar AAC Brandon. Precipitation was low during this study (64%–78% of long-term average (LTA)), resulting in modest yields and low lodging pressure. However, low plant density (PD), split N, and CCC applications all showed potential to reduce lodging risk without reducing grain yield or protein concentration. Split N and plant growth regulator (PGR) applications increased final grain N yield by 11.2% and 2.4%, respectively. Therefore, CM practices have potential in the Canadian Prairies to reduce lodging risk without compromising grain N, but results should be validated in higher precipitation environments and across additional cultivars and growing regions of western Canada.

Rapid Detection of Wheat Ears in Orthophotos From Unmanned Aerial Vehicles in Fields Based on YOLOX.

Wheat ears in unmanned aerial vehicles (UAV) orthophotos are characterized by occlusion, small targets, dense distribution, and complex backgrounds. Rapid identification of wheat ears in UAV orthophotos in a field environment is critical for wheat yield prediction. Three improvements were achieved based on YOLOX-m: mosaic optimized, using BiFPN structure, and attention mechanism, then ablation experiments were performed to verify the effect of each improvement. Three scene datasets were established: images were acquired during three different growing periods, at three planting densities, and under three scenarios of UAV flight heights. In ablation experiments, three improvements had increased recognition accuracies on the experimental dataset. Compared the accuracy of the standard model with our improved model on three scene datasets. Our improved model during three different periods, at three planting densities, and under three scenarios of the UAV flight height, obtaining 88.03%, 87.59%, and 87.93% accuracies, which were, respectively, 2.54%, 1.89%, and 2.15% better than the original model. The results of this study showed that the improved YOLOX-m model can achieve UAV orthophoto wheat recognition under different practical scenarios in large fields, and that the best combination were obtained images from the wheat milk stage, low planting density, and low flight altitude.

Partially functional NARROW LEAF1 balances leaf photosynthesis and plant architecture for greater rice yield.

NARROW LEAF1 (NAL1) is an elite gene in rice (Oryza sativa), given its close connection to leaf photosynthesis, hybrid vigor, and yield-related agronomic traits; however, the underlying mechanism by which this gene affects these traits remains elusive. In this study, we systematically measured leaf photosynthetic parameters, leaf anatomical parameters, architectural parameters, and agronomic traits in indica cultivar 9311, in 9311 with the native NAL1 replaced by the Nipponbare NAL1 (9311-NIL), and in 9311 with the NAL1 fully mutated (9311-nal1). Leaf length, width, and spikelet number gradually increased from lowest to highest in 9311-nal1, 9311, and 9311-NIL. In contrast, the leaf photosynthetic rate on a leaf area basis, leaf thickness, and panicle number gradually decreased from highest to lowest in 9311-nal1, 9311, and 9311-NIL. RNA-seq analysis showed that NAL1 negatively regulates the expression of photosynthesis-related genes; NAL1 also influenced expression of many genes related to phytohormone signaling, as also shown by different leaf contents of 3-Indoleacetic acid, jasmonic acid, Gibberellin A3, and isopentenyladenine among these genotypes. Furthermore, field experiments with different planting densities showed that 9311 had a larger biomass and yield advantage under low planting density compared to either 9311-NIL or 9311-nall. This study shows both direct and indirect effects of NAL1 on leaf photosynthesis; furthermore, we show that a partially functional NAL1 allele helps maintain a balanced leaf photosynthesis and plant architecture for increased biomass and grain yield in the field.

Influence of Planting Scheme on Some Physical Properties of Norway Spruce (Picea abies (L.) H. Karst) Wood

This study analyses the influence of a planting scheme on physical properties of Norway spruce wood. The research material consisted of 326 Norway spruce trees (Picea abies (L.) H. Karst) selected from an experimental plot with four planting variants (2500, 3330, 5000, and 7510 trees·ha−1). The research aspects were: (1) wood density (measured by volumetric method and using microdrilling resistance as proxy), (2) microdrilling resistance, and (3) sound speed. There was a decrease in wood density values (from 0.3376 to 0.3367 g·cm−3) and in microdrilling resistance values (from 15.136% to 14.292%) as the number of trees·ha−1 used for plantation increased from 2500 to 5000. The planting variant with 7510 trees·ha−1 had the largest value (0.3445 g·cm−3 for wood density and 15.531% for microdrilling resistance). Sound speed decreased from 1032.8 to 989.8 m·s−1 as the number of trees·ha−1 increased from 2500 to 7510. These results show a relationship between DBH values and studied physical properties. This relationship is more evident for variants with low planting density (e.g., 2500, 3330 trees·ha−1) than that of dense planting variants (e.g., 7510 trees·ha−1). The explanation may be that the growth of trees in dense plantings is slower; in less dense planting variants, the increase in wood is greater, and as a result, wood volumetric density dependence on the DBH value is greater.

Spatial arrangements between rows x radish plants

Given the importance of this crop and the need for phytotechnical knowledge about the plant spatial arrangement. The objective of this study was to evaluate the productive parameters of the radish culture when submitted to different spatial arrangements between plants and rows. To achieve this aim, the hybrid cultivar Red Pearl was used as a test in a randomized block experimental design, in a 4 x 6 factorial scheme, with four replications. The factors comprise the combination of crop spacing between “rows” and “plants”. The factor levels correspond to the distances between rows: 8, 16, 24, and 32 cm; and between plants: 4, 6, 8, 10, 12, and 14 cm. Root yield, average root mass, longitudinal and transverse diameters, and non-commercial roots were determined. The data obtained were tabulated to obtain the averages, which were submitted to the Shapiro-Wilk residual normality test, at 5% significance, followed by the analysis of variance. When the residual was normal and the response variable was significant, the data was analyzed using linear regression and the appropriate polynomial model was adjusted to present the results. Statistical analyzes were carried out using the R Software. The results show that there was no interaction between the spacing factors for the analyzed parameters, and the spacing between rows and plants influenced the attributes evaluated independently. The spatial arrangements with lower plant densities provided greater root mass and diameter. The importance of new studies involving fixing the spacing between rows and varying the spacing between plants is suggested to better understand the effect of new spatial arrangements on the productive parameters of the radish crop.

Visual preferences for outdoor space along commercial pedestrian streets under the influence of plant characteristics.

Chinese commercial pedestrian streets have developed rapidly in recent years. However, people’s preferences were not sufficiently considered and reflected in the outdoor space and landscape design. With the outdoor landscapes along commercial pedestrian streets in the region south of the Five Ridges as the research objects, this study revealed the public’s different preference evaluations of the landscapes under the reciprocal effects of street characteristics. The main results were as follows: (a) When arcade spaces were available, people prefer streets with taller trees and a lower planting density (50 plants/km or less). Conversely, they preferred streets with relatively low trees (3–6 m), a higher planting density (100–200 plants/km) and two or more vertical layers of plants. People did not like the way that plants are lined in the middle of a street. (b) When there were only one or two types of signage hanging, people preferred streets with a moderate planting density (50–100 plants/km); and there were three or more types of signage hanging, people preferred the plants with low linear density (50 plants/km or less) and that were arranged along one or two sides of the street. (c) When benches were available, people preferred streets with plants on one or both sides, fewer plant colours (one or two kind of colours) and better plant growth status. Specifically, the richer the vertical structure and the bigger number of colours were, the higher the preference score. This study provided design schemes to enhance the visual quality of landscapes by improving landscape characteristics in similar outdoor spaces.

Influence of water storage and plant crop factor on green roof retention and plant drought stress

Green roofs can reduce stormwater runoff with deeper substrates providing greater storage for water retention and evapotranspiration (ET) regenerating storage capacity between rainfall events. In green roof models, ET can be estimated using species-specific plant crop factors (Kc), which characterize water use under non-limiting conditions. We manipulated Kc by altering plant density in a glasshouse experiment under well-watered conditions. We determined Kc of green roof plants growing in pots with different substrate depths (150 mm and 300 mm) and plant densities (0, 1, 2 and 4 plants per pot). We then analyzed the influence of storage and Kc on retention and drought stress using a water-balance model, with a 30-year climate scenario for Melbourne, Australia. We hypothesized that greater planting density and substrate depth would result in proportionally greater ET and therefore higher Kc (glasshouse experiment) and that this would improve retention and reduce drought stress (rainfall simulation). Contrary to our hypotheses, cumulative ET increased by only 38–48% with increased substrate depth and by only 28–38% with increased plant density, despite large increases in plant biomass (67–150%) and growth. Kc values ranged from 1.9–2.2 and 2.7–3.8 for shallower and deeper substrates, respectively. Due to these very high crop factors, our water balance model showed very high annual rainfall retention (97.5%). However, higher Kc and storage only increased rainfall retention by 3–5% and resulted greater drought stress. Plants in deeper substrates experienced 14–29 more days of drought stress, as these plants depleted substrate moisture more efficiently (i.e., had a higher Kc) compared with shallow substrates. These findings suggest that improvements in rainfall retention for green roofs with deeper substrates or higher plant densities are small relative to the increased risk of plant drought stress. The lowest planting density was optimal for improving rainfall retention and reducing plant drought stress.

Response of maize hybrids under limited irrigation capacities: Yield and yield components

AbstractGrain yield of maize (Zea mays L.) in the semiarid Texas High Plains (THP) is greatly reduced when irrigation cannot meet peak water requirements. Drought‐tolerant hybrids may mitigate yield losses resulting from water deficits. We examined the effect of irrigation capacity (8.47 and 4.23 mm d–1) and planting rates (74,000 and 95,000 seeds ha–1) during three growing seasons (2016–2018) on grain yield and yield components of three maize hybrids, two of which were considered drought tolerant. Crop water deficits at the low irrigation level usually extended temporally from seventh leaf collar to dough stage. Mean grain yields varied from 5.2 Mg ha–1 under the low irrigation level to 19.9 Mg ha–1 at the high irrigation level. Hybrid did not influence grain yield and aboveground biomass in all 3 yr. Although kernel number and kernel mass were significantly influenced by hybrid across all years, this did not result in grain yield differences because greater kernel mass compensated for reduced kernel number. Harvest index did not significantly differ between conventional and drought‐tolerant hybrids. In 2016, grain yield was significantly influenced by plant density only at the low irrigation level, with 44% greater yields at the low plant density. For the patterns and level of water stress observed during these three growing seasons, the three hybrids performed similarly. Besides using hybrids well adapted to the region, mitigation of yield reductions under limited irrigation capacities in the THP can be achieved by concentrating irrigation on less land area and optimizing planting rates.

Optimizing planting density and nitrogen application to enhance profit and nitrogen use of summer maize in Huanghuaihai region of China

Low planting density and irrational nitrogen (N) fertilization are two common practices in conventional cropping of smallholder maize production in Huanghuaihai region of China. A 2-year field experiment was carried out to study the effects of N application and planting density on maize phenology, dry matter accumulation, profit, yield, N uptake and efficiency indices. The experiments included three N application levels (120 kg ha−1, N1; 180 kg ha−1, N2; 240 kg ha−1, N3) and three planting densities (60,000 plants ha−1, D1; 75,000 plants ha−1, D2; 90,000 plants ha−1, D3). Increasing N input and planting density delayed the physiological maturity and enhanced dry matter accumulation. Comparing with the traditional N3 level, grain yield and profit were kept stable at N2 level and decreased at N1 level, partial factor productivity of applied N (PFPN) and nitrogen efficiency ratio (NER) were increased with the decreasing of N level. Comparing with the traditional D1 density, grain yield, profit and PFPN were increased at D2 density and then kept stable at D3 density, NER was kept stable at D2 density and then decreased at D3 density. Based on the predicted maximum profit, the optimal combinations of N application and planting density were 199 kg ha−1 and 81,081 plants ha−1 in 2017, and 205 kg ha−1 and 84,782 plants ha−1 in 2018. The two optimal combinations had an increase of 17.6% for grain yield, 39.8% for PEPN, 3.6% for NRE than the traditional N3D1 treatment. Therefore, an appropriate combination of increased planting density with reduced N application could enhance profit and nitrogen use of summer maize in Huanghuaihai region of China.

Caragana korshinskii Kom. plantation reduced soil aggregate stability and aggregate-associated organic carbon on desert steppe.

BackgroundAfter implementing of the “Grain-for-Green” project, Caragana korshinskii Kom. has been widely planted in China’s arid regions. Although natural restoration grassland and artificial Caragana plantations measures have long been focuses in carbon research, the combined influence of natural restoration grassland and artificial Caragana plantation measures on aggregate stability and the aggregate-associated organic carbon (OC) remains unclear.MethodWe selected natural grassland (NG) and three different densities of Caragana plantations (high planting density, HG; middle planting density, MD; low planting density, LD) on desert steppe. The soil aggregate distribution and stability index such as fractal dimension (D), mean weight diameter (MWD), geometric mean diameter (GMD), percentage of aggregation destruction (PAD), as well as aggregate-associated OC concentration and stock were measured.ResultsResults shows that the soil aggregates were primarily macroaggregates (>2 mm) and mesoaggregates (0.25–2 mm) under dry sieving while microaggregates (<0.25 mm) were preponderant under wet sieving (more than 57%). Overall, compared with Caragana plantations, the MWD (4.43 and 4.51 mm) and GMD (1.72 and 1.83 mm) were both highest in two soil layers under the NG and the D (2.77 and 2.71) was lowest. Compared with the NG, the aggregate-associated OC stocks in the 0–40 cm depths in the LD, MD, and HD decreased by 41.54%, 46.93%, and 42.03%, respectively. SOC stock was mainly concentrated in the soil aggregate with sizes of >2 mm and <0.25 mm. These results suggested that natural grassland restoration measures could improve the soil aggregate stability and aggregate-associated OC concentration better than Caragana plantation restoration measures, which NG may be optimal for increasing carbon sequestration and stabilizing soil aggregates on desert steppe.

Grain Yield, Nitrogen Use Efficiency and Antioxidant Enzymes of Rice under Different Fertilizer N Inputs and Planting Density

Nitrogen fertilizer and planting density are key factors affecting rice yield and nitrogen utilization efficiency. There is still a need to optimize nitrogen fertilizer and planting density management for high yield. We studied the effects of different quantities of nitrogen application (N0 0 kg ha−1, N1 120 kg ha−1, N2 180 kg ha−1) and planting density (low-density: 18.8 hills m−2; high-density: 37.5 hills m−2) on rice yield, photosynthetic characteristics, antioxidant system, and nitrogen use efficiency. ANOVA results indicated that most tested traits were affected by environment, planting density, N application, and their interactions. Comparing the results of low-density planting, high-density planting increased the panicle number by 21.12% but decreased the grain number per panicle and yield by 3.97% and 22.48%, respectively. Similarly, the superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) activities and PFPn (partial factor productivity of nitrogen) decreased by 8.20%, 6.99%, 16.41%, 14.28%, and 5.73%, respectively, while HIn (N harvest index) increased by 1.32%. Compared to no N application, N application treatments increased the panicle number, grain number per panicle, and yield by 9.92%, 17.64%, and 37.83% in the N1 treatment; and increased by 17.15%, 29.09%, and 128.94% in the N2 treatment, respectively. N application significantly increased net photosynthetic rates and enzyme activities of antioxidant antioxidases. Compared with N1, N2 decreased REn (apparent recovery efficiency of N), AEn (agronomic N use efficiency), and PFPn by 8.98%, 11.80%, and 25.14%, respectively, while, compared with N0, N1 increased HIn by 8.50%. It was observed that nitrogen fertilizer and planting density had an interaction effect on the net photosynthetic rate, antioxidant enzyme activities, and PFPn and HIn. Given a comprehensive consideration, it is best to apply nitrogen at a rate of 120 kg ha−1 at the planting density of 37.5 hills m−2 for high grain yield and high N use efficiency in our experimental site.

Effect of Plant Density and Nutrient Management on Yield and Economics of Maize (Zea mays L.) Hybrids

The field experiments wereconducted during kharif season (June to October)of both 2016 and 2017 to determine the effect of plant density and nutrient management on yield and economics of maize hybrids at Kalyani AB Block seed farm situated atLatitude 22o57/ N,Longitude 88o20/ E, West Bengal, India.The experiments were arranged at split-split plot design with three replication, two maize hybrids (Pioneer 3077 and Kaveri 50) were in main plot, two plant density (60×20 cm2 and 50×20 cm2) were in sub plot and three nutrient levels (Recommended Dose of Fertilizer i.e. 120:60:60 N:P2O5:K2O kg ha-1, Soil test crop response i.e. 170:60:68 N:P2O5:K2O kg ha-1 and Site Specific nutrient management i.e. 130:44:66N:P2O5:K2O kg ha-1 ) were in sub-sub plot. Result indicated that maize hybrid pioneer 3077 recorded higher grain yield, stover yield and net return and B:C ratio of maize than other hybrid. Higher plant density 50×20 cm2 produced significantly higher yield and economics of maize than lower plant density. Among the nutrient management, Soil Test Crop Response (STCR) was found significantly superior than others and recorded highest grain yield, stover yield and economics of maize. Soil Test Crop Response based nutrient management increased in grain yield was 24.26% over Recommended Dose of Fertilizer (RDF) and 12.29% over Site Specific nutrient management (SSNM).

Rainfall Interception Characteristics of Dracaena Sanderiana and Breynia Distincha

Interception of plants commonly used in urban landscape has not been widely studied compared to forested and cultivated area. Understanding the interception characteristics of these plants can facilitate the selection of the right plant type or combination in order to promote interception as a mean to improve the urban water cycle and urban built environment. Two (2) tropical plants are considered in this study, namely, Dracaena Sanderiana and Breynia Distincha, both with distinct plant structure, plant height, canopy size, number of leaves per plant, leaf size and leaf shape. Rainfall interception characteristics are investigated in laboratory environment using standard hydrology apparatus for different plant density. Artificial rainfall intensity of fixed duration is varied to measure the volume and duration of outflow, and volume intercepted. Results show that runoff begins earlier for higher rainfall intensity and lower plant density. The volume and duration of outflow increases with rainfall intensity and interception increases with canopy cover ratio and leaf area ratio for both plants. At lower plant density, Breynia Distincha has lower interception compared to Dracaena Sanderiana. However, at high plant density, Breynia Distincha demonstrates much better interception capacity even though the canopy cover and leaf area ratios are smaller than Dracaena Sanderiana. The phenomenon may be attributed to coalescence of water droplets that either flow down as stemflow or drip off the leaves under gravitational action. The firm small leaves of Breynia Distincha oriented at near horizontal are more likely to retain the intercepted rainwater compared to the slender soft leaves of Dracaena Sanderiana. This shows that closely spaced Breynia Distincha can be effective in increasing urban interception.

Plant density and manure application affected yield and essential oil composition of Bakhtiari savory (Satureja bachtiarica Bunge.)

The use of soil amendments and cultivated techniques are effective strategies in improving plant yield. Bakhtiari savory (Satureja bachtiarica Bunge.) is an endemic medicinal plant of Iran with various medicinal purposes. To observe the effect of cattle manure (30 t ha−1) and plant density (high plant density, HPD: 80,000; medium plant density, MPD: 40,000, and low plant density, LPD: 26,666 plants ha−1), an experiment was accomplished as split plot with three replicates during 2018 and 2019 on plant yield, nutrients concentration, essential oil (EO) yield and composition, and also stomatal properties of Bakhtiari savory in the dryland farming conditions. The maximum plant weight was observed with manure application at HPD plant density in the second year. The greatest concentrations of N, Ca, and Mg were obtained in the plans treated with manure application and HPD. The increase of plant density led to decreased EO content and increased EO yield. The highest EO yield was observed in second-year plants supplied with manure at HPD. The GC and GC/MS analysis showed that the main constitutes of Bakhtiari savory EO were p-cymene (18.6–43%), carvacrol (32.3–59.3%), γ-terpinene (5–14.3%), thymol (0.6–17.8%), and linalool (2–4.3%), representing different concentrations under the manure and plant densities. Leaf stomatal density and length at LPD was lower compared with HPD and MPD, while increased density of EO glands was obtained at LPD. To sum up, cattle manure and HPD can result in higher plant production.

Impact of Human Settlements on Diversity of Range Vegetation

The rapidly increasing population of human beings in semi-arid areas is often considered as a major factor of land degradation. Only a few studies have examined the dynamics of human settlements on the composition, diversity, structure and palatability of range vegetation in Southern Punjab Pakistan. The current study aims to assess whether the distance from settlements had any effect on the range vegetation’s diversity and cover. In order to determine the impact of human settlements on the vegetation, the sampling area (Thal rangeland) was classified into three categories, i.e., Near (1–2 km from human communities), Away (2–4 km from human communities), and Far (4–6 km from human settlements). A total of 75 transects in all of the three sites were placed in the study sites. Along the transects, a quadrate of 1 m2 after every 10 m was randomly placed. The study site yielded floral diversity of a total of 29 species, representing 23 genera and belonging to 9 families. Results showed that the areas away from the human communities had higher species diversity (20), while the site near to human settlements depicted lower diversity (14). It was observed that, although the site near to communities had lower diversity, it depicted higher plant density, while the highest diversity along with the lowest plant density was observed in sites away from the communities. The study concluded that the diversity of range grasses, especially desirable species, was affected by distance to human settlements. These findings could be useful to detect flora changes, establish habitat protection priorities and improve efforts for conserving natural landscapes.

Plant topping effects on growth, yield, and earliness of field-grown cotton as mediated by plant density and ecological conditions

Manual removal of the main-stem growth tip is traditionally used to break the apical dominance of cotton ( Gossypium hirsutum L.). Chemical topping with plant growth regulators also effectively inhibits apical dominance. However, the effect of chemical topping on yield increases and whether plant density or ecological conditions affect its efficacy are unclear. Therefore, a three-year field experiment with a split-plot design was conducted to determine the effects of plant topping, plant density, and their interactions on cotton yield and related physiological and agronomical parameters at three sites with different ecological conditions in China. In each site, the main plots were assigned low, moderate, or high plant density and the subplots were assigned no topping, manual topping, or chemical topping. Growth, yield, yield components, earliness, and late-season leaf photosynthesis as well as labor and material inputs were examined each year. Compared with no topping, both chemical and manual topping greatly reduced plant height at all sites. Manual topping increased seed cotton yield and earliness in all tested plant densities and sites. However, plant density but not ecological condition greatly mediated the effect of chemical topping on yield. At low plant density, the yields with chemical topping were 4–6% lower than those with no topping and 5.5–10.8% lower than those with manual topping at the three sites. Although yields with chemical topping were comparable with those of manual topping at moderate and high plant densities, they were 8.6–12.8% higher at moderate density and 13.8–16.4% higher at high plant density than those with no topping across years and sites. Averaged across the sites, chemical topping reduced biological yield by 12.7% at low plant density. Although biological yield decreased slightly, chemical and manual topping increased the harvest index by 12.4% and 13.3% at moderate density and by 15.6% and 17.4% at high density, respectively. In comparison with no topping, the reduction in seed cotton yield with chemical topping at low plant density was attributed to insufficient biological yield, whereas the increase in yield at moderate and high plant densities was mainly due to greater partitioning of assimilates to reproductive tissues. Compared with manual topping, chemical topping produced 23.2% lower net returns as a result of lower seed cotton yield at low plant density but produced 8.1% and 20.9% higher net returns at moderate and high plant densities, respectively, because of savings in labor inputs and comparable seed cotton yields. In addition, chemical topping increased the earliness percentage compared with that of no topping. Overall, this study demonstrates that chemical topping is a promising alternative to traditional manual topping under moderate or high cotton plant density. • Manual topping increased cotton yield regardless of plant densities and ecological conditions relative to non-topping. • Chemical topping decreased yield at low plant density relative to non-topping because of greater biomass reduction. • Chemical topping increased cotton yield at moderate and high plant densities via greater assimilates partitioning to fruits. • Chemical topping could replace manual topping at moderate and high plant densities without ecological dependence.