Low Plant Density Research Articles

Improving Pinus taeda site index from rotation to rotation with silvicultural treatments

We wanted to improve site index using fertilizer applications and planting density at a site with a site index of 16.8 m at a base age of 25 years. We installed a randomized complete block study in the Virginia Piedmont with three replications of three levels of fertilization (cumulative elemental nitrogen and phosphorous amounts of 0 and 45, 309 and 73, and 787 and 129 kg ha−1, respectively) and two levels of planting density (896 and 1793 trees ha−1). We measured the stand 15 times and completed our analysis after age 22 measurements. Fertilization and planting density did not affect site index and there was no planting density by fertilization interaction. Fertilizer significantly increased stem diameter and basal area but did not affect dominant height. Low planting density resulted in significantly larger diameter trees with longer crowns, but with less basal area and stand scale production than the high planting density. However, site index in all treatments improved to 24.2 m, a 7.4 m increase from one rotation to the next. We attributed the increase in site index to adding the primary limiting resource (phosphorous), better competition control, genetics and growing environment. Silvicultural inputs and environmental conditions influence site index and estimates of productivity (e.g. m3 ha−1 yr−1) may be more useful.

Di-ammonium phosphate (DAP) and plant density improve grain yield, nodulation capacity, and profitability of peas (Pisum sativum L.) on ferralsols in eastern D.R. Congo

Sustaining high crop yield and profitability on marginal soils, such as degraded ferralsols, calls for the use of adequate farming practices. In this study, we assessed for four cropping seasons the effect of di-ammonium phosphate (DAP) fertilizer application doses (100, 150, and 200 kg ha−1) and plant densities (100,000, 166,666, and 250,000 plants ha−1) on growth, yield, nodulation capacity, and profitability of two pea varieties (Adei and Rwanda) under degraded ferralsols in eastern Democratic Republic of Congo (DRC). Results showed that pea growth, yield, nodulation, and profitability were significantly affected by the DAP dose and the plant density. Application of 150 kg ha−1 of DAP improved pea yields from 730 to 1720 kg ha−1 and nodulation from 17 to 22 nodules per plant. The number of active nodules was positively correlated with total number of nodules, DAP doses, yield parameters, and plant height. High grain yield was recorded during the long rainy season (1400 kg ha−1) compared to the short one (930 kg ha−1). All DAP doses were profitable according to the agronomic efficiency (AE) and value–cost ratio (VCR) analyses. For improved and profitable pea production on degraded South-Kivu ferralsols, applying 150 kg ha−1 of DAP combined with low plant density are to be recommended and preferably in the long rainy season.

Screening of Finger Millet (<em>Eleusine coracana</em>) Germplasm for the Blast Disease-Resistance in Sri Lanka

Finger millet is the third important cereal crop in Sri Lanka, mostly cultivated in rainfed uplands in dry and intermediate zones. Blast disease (leaf, finger, and neck blast) caused by Magnaporthe grisea is economically devastating to rice and finger millet worldwide. Host resistance is the most viable option for managing the disease as it is mainly grown in low-input systems. One hundred thirty-nine finger millet accessions collected from the Plant Genetic Resources Center in Sri Lanka were field screened for leaf blast disease in three seasons under artificial inoculation at the Field Crops Research and Development Institute at Mahailluppallama, Sri Lanka. The results revealed that almost all the tested accessions were susceptible to leaf blast at the early seedling stage. However, 5–6 weeks after sowing, the severity of leaf blast disease decreased drastically, and all the germplasm were resistant or moderately resistant. The finger blast and neck blast severity, scored under natural infection, was low under both high and low-density planting. Seven and 87 finger millet accessions consistently showed immune reactions for finger blast and neck blast, respectively. A negative correlation was observed between the days to flowering and blast disease. The early flowering accessions, namely, Ac12968 and Ac2384 from Jaffna, TVFM, 13-1, TVFM-04, and TVFM-02 from Killinochchi, showed a higher severity score for leaf, finger, and neck blast compared to other accessions. A significant positive correlation (P<0.05) was found between finger blast and neck blast, however, these two diseases did not show a significant correlation (P>0.05) with leaf blast.

Complementary effects of phosphorus supply and planting density on maize growth and phosphorus use efficiency.

Phosphorus (P) supply and planting density regulate plant growth by altering root morphological traits and soil P dynamics. However, the compensatory effects of P supply and planting density on maize (Zea mays L.) growth and P use efficiency remain unknown. In this study, we conducted pot experiments of approximately 60 days to determine the effect of P supply, i.e., no P (CK), single superphosphate (SSP), and monoammonium phosphate (MAP), and different planting densities (low: two plants per pot; and high: four plants per pot) on maize growth. A similar shoot biomass accumulation was observed at high planting density under CK treatment (91.5 g plot–1) and low planting density under SSP treatment (94.3 g plot–1), with similar trends in P uptake, root morphological traits, and arbuscular mycorrhizal colonization. There was no significant difference in shoot biomass between high planting density under SSP (107.3 g plot–1) and low planting density under MAP (105.2 g plot–1); the corresponding P uptake, root growth, and P fraction in the soil showed the same trend. These results suggest that improved P supply could compensate for the limitations of low planting density by regulating the interaction between root morphological traits and soil P dynamics. Furthermore, under the same P supply, the limitations of low planting density could be compensated for by substituting MAP for SSP. Our results indicate that maize growth and P use efficiency could be improved by harnessing the compensatory effects of P supply and planting density to alter root plasticity and soil P dynamics.

Contribution of tillers to maize yield stability at low plant density

AbstractOne of the main challenges of using low plant densities in restrictive and variable environments is to maximize the use of resources in better‐than‐expected years. In this context, tillering could be an alternative to increase reproductive and vegetative plasticity. The objectives of this study were to (a) characterize the correlation between environmental conditions, tiller traits, crop grain yield, and grain yield advantages due to tillers; (b) determine the grain yield response to tillering (i.e., grain yield difference between tillered and nontillered crops) for a wide range of environments; and (c) to evaluate the effect of tiller presence on grain yield of the main shoot, considering its effect on the apical and subapical ears. Tillered and nontillered crops were evaluated under rainfed conditions during two seasons (2018–2019 and 2019–2020). These experiments were carried out at 11 sites in the southern Argentinean Pampas, varying sowing date (22 Oct. to 5 Dec.), plant density (2–3 plants m−2), genotype (AX7784 and AX7761), and soil depth. Grain yield (3.2–11.9 Mg ha−1) was correlated with tillers productivity, mainly explained by postflowering precipitations. The contribution of tillers to grain yield was more proportional than their consequent yield depression at the main shoot. Tillers either increased (3 sites) or maintained (8 sites) grain yield, and their contribution increased as the environment improved without any detrimental effect in the most restrictive environments. Tillering has the potential for increasing resource (radiation, water, nitrogen) use efficiency under low plant density strategies adopted for restrictive environments.

Comparative Evaluation of Pear Performances Under High- and Low-Density Planting Systems cv. ‘Santa Maria’

Comparative Evaluation of Pear Performances Under High- and Low-Density Planting Systems cv. ‘Santa Maria’

Nitrogen Fertilizer and Sowing Density Affect Flag Leaf Photosynthetic Characteristics, Grain Yield, and Yield Components of Oat in a Semiarid Region of Northwest China

Oat has been gaining renewed interest due to its role in a healthy human diet, in animal feed, and as a source of high value compounds with industrial applications. Nitrogen fertilization and planting density are two of the most important crop management practices that affect the formation of yield components and final yield of oat. A 2 year 3 × 5 factorial field experiment was conducted to investigate the effects of nitrogen (N) fertilizer and planting density on the flag leaf photosynthetic characteristics, grain yield, and yield components under rainfed conditions. The experiment consisted of three sowing densities (60, 180, and 300 kg·ha−1) and five nitrogen fertilizer rates (0, 45, 90, 135, and 180 kg·ha−1). Results showed that the grain yield was significantly (p < 0.05) correlated with the leaf net photosynthesis rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), water-use efficiency (WUE), stomatal limitation value (Ls), chlorophyll content (SPAD value), leaf area index (LAI), panicle length, number of spikelets per panicle (NSP), number of grains per panicle (NGP), weight of grains per panicle (WGP), and 1000-kernel weight. Among the yield components, grain yield was driven by number of spikelets per panicle (NSP) and number of grains per panicle (NGP) at low (or high) planting density with low N supply, whereas, at high N supply, 1000-kernel weight was also an important factor for yield. Nitrogen fertilizer and sowing density had significant (p < 0.05) effects on the flag leaf photosynthetic characteristics, grain yield, and yield components of oat. The yield components increased and then decreased with the increase in nitrogen fertilizer, while they decreased with the increase in planting density. The maximum values (p < 0.05) of grain yield were observed in the nitrogen fertilization of 90 kg·ha−1 and sowing density of 180 kg·ha−1 treatment in both growing seasons, mainly contributing to the improved leaf photosynthesis traits (Pn, Gs, Tr, Ls, SPAD, and LAI). The combination of nitrogen fertilization of 90 kg·ha−1 and sowing density of 180 kg·ha−1 is suitable for oat production on a cool semiarid plateau or other agroecozones with similar environmental conditions.

Rapid in situ nondestructive evaluation of lodging risk in dryland agronomic wheat research

AbstractThe natural occurrence of lodging in wheat (Triticum aestivum L.) in small‐plot research aiming to record visual ratings is unpredictable highly dependent on environmental conditions, and does not differentiate between root and shoot lodging. Detailed plant characteristics can be used to indicate lodging risk; however, such measurements are destructive and time‐consuming for projects that are not focused solely on evaluating lodging. The Stalker, a push force meter, can be used nondestructively to rapidly indicate stem strength and elasticity, which may be useful for measuring lodging risk in small‐plot research to indicate both root and shoot lodging. The objective of this study was to evaluate the ability of the Stalker to detect agronomic management practices that are known to reduce lodging risk (reduced plant density, split nitrogen applications, and plant growth regulator applications). Stalk strength (resisting force) and elasticity (spike displacement, energy, and power) measurements were taken at anthesis and physiological maturity in a small‐plot agronomic research trial. The Stalker was able to identify practices with high and low lodging risk. Lower plant density led to increased stem strength (measured by resisting force) and stem flexibility (measured by spike displacement) compared with high plant densities, indicating a decreased risk of both stem and root lodging when low plant densities were used. Overall, the Stalker is a new tool for rapid and nondestructive measurements of lodging risk in small‐plot agronomic research trials and can indicate both stem and root lodging risk by measuring indicators of both stem strength and elasticity.

Behavioral responses to riparian and anthropogenic edge effects in mantled howler monkeys (Alouatta palliata) in a disturbed riverine forest.

Fragmented forests contain natural edges, including riparian zones, and anthropogenic edges. Edges generally have lower plant density and fewer large trees than forest interior. Riparian edges, however, contain gap-specialist trees yielding leaves with high protein content, providing primates with important resources. We examined mantled howler monkeys' behavioral responses to riparian and anthropogenic edges at La Suerte Biological Research Station (LSBRS), Costa Rica. We predicted the monkeys would spend more time resting and feeding and less time traveling, and be less spatially cohesive, in both anthropogenic and riparian edges compared to forest interior due to lower resource abundance in edges, and in anthropogenic compared to riparian edge due to higher leaf quality in riparian zones. From 2017 to 2020, we collected data across forest zones on activity and spatial cohesion patterns via focal sampling, recording data every 2min. Howler monkeys were significantly more likely to rest and significantly less likely to travel in both anthropogenic and riparian edges compared to forest interior; however, there were no differences between these edge types. There were significantly more monkeys within a 5-m radius of focal subjects in both anthropogenic and riparian edges compared to forest interior, but no differences between these edge types. While prior research found no differences across zones when only anthropogenic edge and forest interior were compared, results of this study demonstrate that howler monkeys at LSBRS modify their activity patterns in anthropogenic and riparian edge zones compared to forest interior, highlighting the importance of focusing on both natural and anthropogenic edge zones to fully understand primates' behavioral responses in fragmented landscapes.

Sentinel-1 interferometric coherence as a vegetation index for agriculture

In this study, the use of Sentinel-1 interferometric coherence data as a tool for crop monitoring has been explored. For this purpose, time series of images acquired by Sentinel-1 and 2 spanning 2017 have been analysed. The study site is an agricultural area in Sevilla, Spain, where 16 different crop species were cultivated during that year. The time series of 6-day repeat-pass coherence measured at each polarimetric channel (VV and VH), as well as their difference, have been compared to the NDVI and to the backscattering ratio (VH/VV) and other indices based on backscatter. The contribution of different decorrelation sources and the effect of the bias from the space-averaged sample coherence magnitude estimation have been evaluated. Likewise, the usage of 12 days as temporal baseline was tested. The study has been carried for three different orbits, characterised by different incidence angles and acquisition times. All results support using coherence as a measure for monitoring the crop growing season, as it shows good correlations with the NDVI (R2>0.7), and its temporal evolution fits well the main phenological stages of the crops. Although each crop shows its own evolution, the performance of coherence as a vegetation index is high for most of them. VV is generally more correlated with the NDVI than VH. For crop types characterised by low plant density, this difference decreases, with VH even showing higher correlation values in some cases. For a few crop types, such as rice, the backscattering ratio outperforms the coherence in following the growth stages of the plants. Since both coherence and backscattering are directly computed from the radar images, they could be used as complementary sources of information for this purpose. Notably, the measured coherence performs well without the need of compensating the thermal noise decorrelation or the bias due to the finite equivalent number of looks.

Maize prolificacy under contrasting plant densities and N supplies: I. Plant growth, biomass allocation and development of apical and sub-apical ears from floral induction to silking

In limited-production regions for maize (Zea mays, L.) crop, late sowing date and low plant densities are progressively adopted. At low plant densities, the expression of prolificacy (i.e., more than one fertile ear per plant) can stabilize maize yield throughout environments. However, the limited adoption of N fertilization can reduce kernel set on the apical (E1) and sub-apical ear (E2) and consequently crop grain yield at low plant densities. Five Argentinian maize hybrids with different degrees of prolificacy (1.37–1.92 ears pl-1 at 4 pl m-2 irrigated and without N limitations) were cultivated under contrasting plant densities (4 and 8 pl m-2) and N fertilization rates (70 and 270 kg N ha-1) to analyze (i) plant biomass, biomass allocation in E1 and E2 (BAE1 and BAE2), and floret differentiation of both ears from floral induction to silking stage, (ii) the anthesis-silking intervals of E1 and E2 (ASIE1 and ASIE2) and the silking interval between E1 and E2 (ESI), and (iii) silk extrusion of both ears. From the eight-ligulated leaf stage onwards, low N availability and high density decreased plant biomass and BAE2 without modifying BAE1. Additionally, N stress reduced floret differentiation of E2 in the less prolific hybrids (DK-747 and DK-7210). On the contrary, E1 and E2 of the most prolific hybrids (DK-3F22, DK-4F37 and DK-664) showed similar temporal patterns of growth and floret differentiation. These hybrids presented the highest proportion of exposed silks in both ears coinciding with their highest BAE1 and BAE2, which possibly modulated silk elongation. Finally, under the most stressful environments, the lower BAE2 than BAE1 at silking increased ASI of both ears, ESI and reduced the proportion of plants with silks of E2 exposed to pollen. The latter response (i.e., low proportion of plants with silks extrusion in E2) was more pronounced in less prolific hybrids. Therefore, floret differentiation and BA in E2 of the most prolific hybrids would be more stable in the face of changes in nutritional offer, a prevalent scenario of limited-production regions.

Maize prolificacy under contrasting plant densities and N supplies: II. Growth per plant, biomass partitioning to apical and sub-apical ears during the critical period and kernel setting

Maize ( Zea mays L.) prolificacy (i.e., more than one fertile ear per plant) is a source of reproductive plasticity that contributes to increase or sustain crop grain yield when plant density is reduced in drought-prone environments. The rare use of N fertilization, however, can limit prolificacy. In a companion paper we studied floret differentiation and biomass allocation in apical (E1) and sub-apical ear (E2) and flowering dynamics of five maize hybrids with contrasting prolificacy under different plant densities and N supplies. Briefly, after apex induction, E1 and E2 of the most prolific hybrids (DK-3F22, DK-4F37 and DK-664) had similar temporal patterns of growth and floret differentiation. On the contrary, E2 in the less prolific hybrids (DK-747 and DK-7210) had less biomass allocation and floret differentiation than E1, which were reduced under low soil N supply, resulting in a fewer proportion of plants with silk extrusion of E2. In this work, we explore the relationships between (i) kernel number per plant vs the growth rates of plants around flowering, (ii) growth rate of ears vs plant growth rate around flowering (i.e. biomass partitioning to E1 and E2), (iii) kernel number of E1 and E2 vs the growth rates of ears around flowering (i.e. reproductive efficiency of E1 and E2), and (iv) kernel number and prolificacy vs flowering synchrony (i.e., ASI: anthesis-silking interval and ESI: ear silking interval between E1 and E2). For all hybrids, N supply modulated plant growth rate and biomass partitioning to both ears around flowering, kernel number per unit of plant growth rate around flowering and reproductive efficiency of E2, with no impact on the reproductive efficiency of E1. Reductions of kernel number per plant were related to failures of early emerged silks (of E1 under low N supply and of E2 under both N supplies) to set kernels. Failures in kernel setting of E2 were also related to a reduced biomass partitioning to E2 around flowering. Higher ASI E1 values described crops with lower kernel numbers of E1, while higher ESI values depicted both a lower proportion of plants with more than one fertile ear (i.e., prolificacy) and lower kernel numbers of E2. Results complement evidence from the companion paper of the role of N supply on plant biomass production and biomass partitioning to E2 from early floral development stages to the period around flowering, and on the reproductive efficiency of E2. Consequently, N supply must be ensured from early vegetative stages of low-density maize crops, so as not to compromise prolificacy and E2 kernel setting. • Prolificacy was highly sensitive to N supply even at low plant density. • High N supply increased biomass partitioning to ears around flowering. • Only reproductive efficiency of sub-apical ear (E2) was improved by N supply. • Ear silking interval modulate prolificacy expression and kernel setting of E2.

Effects of plant density, seed spacing, and seed treatment on thrips injury to cotton

Previous observations in small-plot field trials in Tennessee suggest that thrips injury is higher in plots with lower plant densities and when singular plants are spatially isolated and uniformly distributed compared to a group of plants that are clumped together; however, research documenting this is limited. Thus, studies were performed in Jackson and Milan, TN across two years (2020, 2021). Both studies had fungicide-treated seed planted with or without an imidacloprid insecticide seed treatment. The first study investigated the effects of plant density by planting seed at rates considered to be low, normal, high, and very high. The second study investigated the effects of seed placement strategies with seed planted at the same density. Cotton plates were used to plant seed to result in singular plants that were spatially isolated and uniformly planted or clumped, “hill-dropped” plants. Results from the plant density tests showed thrips injury ratings were higher as the plant density decreased. At two test sites, the number of adult thrips was higher in plots with lower plant densities, indicating that thrips were more concentrated on individual plants. However, high thrips pressure and unfavorable growing conditions at the other sites seemed to overwhelm the potential effects of plant populations. Results from initial thrips injury ratings in the seed spacing study showed significantly higher injury for singular, uniformly distributed plants than plants in a hill (i.e., cluster); however, additional research is needed because one test was lost. Future research evaluating oviposition rates on recently emerged seedlings could help explain why decreased thrips injury occurs when plant densities are relatively high.

Growth dominance and growth efficiency in response to thinning treatments in Chinese fir plantations with long-term spacing trials

Growth dominance is a relatively new, simple, quantitative metric of within stand resource partitioning, while growth efficiency can be used to quantify the efficiency of resource use at both stand and tree level. We examined long-term silvicultural experiments in Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) to characterize how growth dominance and stand growth efficiency in stands thinned from below develop with age, cumulative thinning intensities, residual density, and planting density. Results showed that growth dominance in unthinned plots increased with increasing age, while stand growth efficiency displayed the reverse pattern. Both of them were not significantly different between planting densities, which indicates that the efficiency of resource use and relative growth of Chinese fir was always proportional to its size, even in dense stands. Thinning improved the relative growth of larger trees and decreased stand growth efficiency. When the dense plots were thinned to the next lower initial planting density, the growth dominance of the thinned plots were higher than that of the unthinned plots, and stand growth efficiency of the thinned plots were lower than the respective unthinned plots. When plots with different planting densities were thinned to the same stand density, growth dominance increased with cumulative thinning intensities, while stand growth efficiency showed the reverse pattern. Growth dominance was positively correlated with the growth efficiency difference between smaller and larger trees in both unthinned and thinned plots, while negatively correlated with stand growth efficiency.

Effects of Contaminated Soil on the Survival and Growth Performance of European (Populus tremula L.) and Hybrid Aspen (Populus tremula L. × Populus tremuloides Michx.) Clones Based on Stand Density.

This study was conducted to assess the survival rates, growth, and chlorophyll fluorescence (Fv/Fm) of four hybrid aspen (14, 191, 27, 291) and two European aspen (R3 and R4) clones cultivated in creosote- and diesel oil-contaminated soil treatments under three different plant densities: one plant per pot (low density), two plants per pot (medium density), and six plants per pot (high density) over a period of two years and three months. Evaluating the survival, growth, and Fv/Fm values of different plants is a prerequisite for phytoremediation to remediate polluted soils for ecological restoration and soil health. The results revealed that contaminated soils affected all plants’ survival rates and growth. However, plants grown in the creosote-contaminated soil displayed a 99% survival rate, whereas plants cultivated in the diesel-contaminated soil showed a 22–59% survival rate. Low plant density resulted in a higher survival rate and growth than in the other two density treatments. In contrast, the medium- and high-density treatments did not affect the plant survival rate and growth to a greater extent, particularly in contaminated soil treatments. The effects of clonal variation on the survival rate, growth, and Fv/Fm values were evident in all treatments. The results suggested that hybrid aspen clones 14 and 291, and European aspen clone R3 were suitable candidates for the phytoremediation experiment, as they demonstrated reasonable survival rates, growth, and Fv/Fm values across all treatments. A superior survival rate for clone 291, height and diameter growth, and stem dry biomass production for clone 14 were observed in all soil treatments. Overall, a reasonable survival rate (~75%) and Fv/Fm value (>0.75) for all plants in all treatments, indicating European aspen and hybrid aspen have considerable potential for phytoremediation experiments. As the experiment was set up for a limited period, this study deserves further research to verify the growth potential of different hybrid aspen and European aspen clones in different soil and density treatment for the effective phytoremediation process to remediate the contaminated soil.

Determination of some heavy metals and microbial profile of raw Sugar samples collected from Sudanese Sugar Industries in season 2017 in relation to EU.1998 and ICUMSA,1974 standards

The study was conducted in Sudanese Sugar Industries during the period 2017 to aim the determination some heavy metals and microbial profiles of raw Sugar samples collected from Sudanese Sugar Industries in season 2017 in relation to EU.1998 and ICUMSA,1974 standards. The samples were obtained from all Sudanese Sugar Industries namely, (Kenana, White Nile, Assalaya, Sennar, Guneid, and New Halfa). After that the samples were transferred to the laboratory to assess the quality parameters of raw sugar which include the determination of some heavy metals content of sugar cane per mg/kg in Sudanese sugar companies which include Mercury, Cadmium, Lead, and Arsenic, Determination Microbial analysis for final sugar which includes Detection of Thermopolis Bacteria (Sporeforming Bacteria, Bacteria producing H2S and H2 swell) and Determination Methophilic Bacteria (Total Count of bacteria CFU/10 gm, Determination Coliform Bacteria CFU/ 10 gm, Determination of Leuconstoc Mesenteroides Bacteria CFU/10 gm. and Enumeration of Yeasts and Moulds CFU/ 10 gm and Determination the concentration of Dextran. and the data were analyzed by using a Statistical system Complete Randomized Design (CRD) and analysis of variance technique by Least Significant Different Test (LSD) according to Fisher’s LSD method, 2010 at (Probability 0.05). Was applied to compare differences between means. The results showed that the mean concentration of Mercury, Cadmium, Lead and Arsenic was (0.02 mg/ kg grams of sugar), (0.62 mg/ kg sugar), (6.74 mg/ kg sugar), and (2.73mg/ kg sugar). These results Indicate all sample industries were agreeable with critical limit maximum value. It was concluded that the total count of Bacteria for raw Sugar White Nile and Sennar agreed with recommended limit. In the case of total yeasts, Sporeforming Bacteria, and Dextranium Bacteria all samples Industries were highest than the critical limit. While the total Moulds and Bacteria Production H2S all samples Industries were less than the critical limit except Kenana and Guneid respectively. Concerning the Total Count of Leuconstoc Mesenteroides Bacteria in sugar, the results revealed all samples Industries were higher than the recommended limit. And the samples Industries were online with the recommended limit concerning the dextran concentration except Guneid industry was highest than the critical limit (75 ppm). The study recommended that the Sudanese Sugar Industry needs to establish proper quality assurance laboratories to help in monitoring the quality and safety of raw materials and end products.In conclusion, the grain yield of maize increased with increasing N rate and plant density up to the optimum. Therefore, it’s possible to recommend using a high N rate with both low and medium plant density (< 45,000 plants ha-1) and (45,000 to 65,000plants ha-1) to harvest high grain yield.

Comparison of Short-Duration and Long-Duration Rice Cultivars Cultivated in Various Planting Densities

The selection of high-yielding, short-duration rice cultivars is essential for the double-rice cropping system. High hill density could be achieved with less labor under machine transplanted conditions. Therefore, dense planting is more practical for machine-transplanted rice. While few studies have been conducted to certify the feasibility of short-duration cultivar combined with dense planting in machine transplanted conditions. The current study was executed to determine the effects of dense planting on yield attributes and grain yield of short-duration cultivars under mechanically transplanted conditions. A field experiment comprises two treatments—i.e., the short-duration cultivar Lingliangyou104 cultivated at a high planting density (SDH) and the long-duration Taiyou390 cultivar cultivated at a low planting density (LDL)—were conducted in the 2018 and 2019 late seasons. The results showed that the SDH exhibited 17% and 19% higher panicle number in a unit, 26% and 24% higher spikelet filling, 8% and 8% higher grain weight, 21% and 11% higher harvest index, and consequently 12% and 4% higher grain yield and 13 and 15 days shortened growth duration compared to the LDL in the 2018 and 2019, respectively. The data revealed that the difference in grain yield between the SDH and LDL was mainly due to the higher harvest index and reasonable dry matter distribution of the SDH, which was conducive to improving yield components and increasing rice grain yield. As a result, short-duration rice cultivars combined with dense planting is a feasible strategy for improving the grain yield of mechanically transplanted late rice.

Enhancing maize yield in Ethiopia a meta-analysis

Accurate nitrogen (N) fertilization and optimum plant density increase crop yields. In this study, I report the effects of N fertilization rate and plant density on maize yield in a meta-analysis, by using observations from 15 studies conducted in Ethiopia since the 2000s for possible refinement of N fertilizer and plant density recommendations. I assessed the response of maize to different N rates ha−1 compared to the control using the yield response approach. Application of N fertilizer significantly increased maize yields by 31.5% - 65.9% compared to control. plant density increased maize yields by 42% - 72.4% compared to the control. The interaction effect of the N rate increased maize yields by 27.6% - 95.9%, with Plant density, 58.7% - 152% on loam soil, compared to control yield. The interaction effect of Plant density with soil type increased maize yields by 47% - 108% on loam soil. In conclusion, the grain yield of maize increased with increasing N rate and plant density up to the optimum. Therefore, it’s possible to recommend using a high N rate with both low and medium plant density (< 45,000 plants ha-1) and (45,000 to 65,000plants ha-1) to harvest high grain yield.

Planting density affects soil quality in the deep soils of pine plantations

Planting density is one of the important factors affecting soil properties, thereby directly impacting plantation yields. However, the effect of planting density on soil quality and productivity in plantation ecosystem mostly remain unknown. The present study aims to assess soil quality in four mature pine (Pinus kesiya) plantations with increasing planting densities i.e., 700 trees ha−1 (low planting density, LPD), 1080 trees ha−1 (moderate planting density, MPD), 1260 trees ha−1 (high planting density, HPD), and 2340 trees ha−1 (very high planting density, VHPD) respectively, up to 1 m soil depth. The soil samples collected at 0–20, 20–60, and 60–100 cm depth intervals were analyzed for a total of thirty-nine physical, chemical, and biological properties. The soil quality index (SQI) was calculated using linear scoring and weighted additive method. Total carbon, arbuscular mycorrhizal fungi (AMF) biomass, gram-positive bacteria biomass, soil moisture content, and β-glucosidase enzyme were selected as the important drivers of SQI. Total carbon, AMF, and moisture content had higher contribution to SQI. The results showed that increasing planting density adversely affected soil quality. SQI was higher in the surface (0–20 cm) soil layer, and it decreased with depth. Planting densities, soil depths, and their interaction had a significant effect on SQI. Increasing SQI promoted the stem biomass with a positive linear response. Therefore, maintaining a moderate to low planting density by thinning practices and selective logging could recover natural understory vegetation, acquire high timber yield, and sustain soil quality in pine plantations.

Effect of spacing on growth performance and leaf biomass yield of Moringa stenopetala tree plantations

Moringa stenopetala is a multipurpose tree distributed naturally in the lowland dry lands of the southern part of Ethiopia. The tree has vital nutritional, industrial, and medicinal applications and is thus good for large scale and/or commercial plantations. However, its cultivation is limited to traditional practices by small holder farmers for food, fodder, shade, windbreak and medicinal value around homesteads and on farmlands. The aim of this study was to determine the effect of plant spacing on plant growth parameters and leaf biomass production of M. stenopetala. The study was conducted in Arbaminch zuria woreda of Southern Nation Nationalities and Peoples Region (SNNPR). Three planting spacings (0.5 × 0.5 m; 1 × 1 m and 2 × 2 m) were arranged in a randomized complete block design (RCBD) and the treatments were replicated three times. Survival%, root-collar diameter (RCD), height and stem diameter of the trees in each plot were recorded at three monthly intervals from the 3rd to 15 months. Data for leaf biomass were collected at the age of 27, 32 and 48 months. The harvested leaves were then oven dried to determine the dry leaf biomass. Individual Moringa trees showed better growth performance at the wider spacing of 2 × 2 m. The mean RCD, plant height and stem diameter were 7.45 ± 0.20 cm, 1.69 ± 0.06 cm and 3.19 + 0.11 cm for the wider spacing, while 3.12 ± 0.16 cm, 1.02 ± 0.07 cm and 2.12 ± 0.14 cm for the narrow spacing at the age of 15 months. The wider spacing produced the largest quantity of dry leaf biomass per individual plant (119.28 ± 9.02, 143.85 ± 10.29 and 249.8 ± 24.220 g/tree, but the least quantity on hectare bases 298.20 ± 22.54, 359.62 ± 25.73 and 624.49± 60.59 kg/ha) while the narrow spacing produced the smallest quantity per individual plant (48.36 ± 5.10, 44.74 ± 3.19 and 88.15 ± 30.28 g/tree), but the largest quantity on hectare bases (1934.40 ± 203.89, 1789.56 ± 127.78 and 3526.01± 1211.2 kg/ha) at the first, second and third harvest, respectively. This indicates that an increase in the plant spacing led to higher dry leaf biomass production per tree due to better plant growth, but the lesser the leaf biomass yields per hectare due to the lower planting density. The performance of M. stenopetala is promising and hence it can be considered for large scale and commercial plantation .