Low Plant Density Research Articles

Adjusting peanut plant density and potassium fertilization for different production environments

AbstractPeanut pod yield and its response to fertilizer‐K can be affected by the environment × plant density interaction. Research was conducted with the objective of determining peanut growth and yield response to planting density and fertilizer‐K application under rainfed conditions in Brazil and irrigation in the United States. The effects of plant planting density and K fertilization were more frequent in rainfed areas, compared to irrigated environments. Peanut leaf area index (LAI) and dry matter accumulation (DM) increased with increasing plant density (mainly at 30 days after plant emergence—average increments of 70% and 80% for LAI and DM, respectively), whereas the stomatal conductance was decreased, mainly in rainfed fields. In low‐K soil, the application of 50 kg ha−1 of K increased leaf K concentration (12% [Brazil], first‐year area and 28% crop rotation area) and stomatal conductance in rainfed fields, resulting in greater yield (23% [1340 kg ha−1; Brazil], first‐year area) at low plant density. In the irrigated fields, yield increased with plant densities up to 19 plants m−2. For rainfed crops, plant density exceeding 11 plants m−2 resulted in lower yield in the area of adequate K content in the soil. Therefore, in rainfed fields, plant density must be low to assure peanuts response to K. In irrigated environments, high plant density is less detrimental to peanut yield, but no increase is observed with plant density greater than 19 plants m−2. Additionally, there was no yield increase with the application of 50 kg ha−1 of K, in irrigated environments.

Estimation of Maize Yield and Protein Content under Different Density and N Rate Conditions Based on UAV Multi-Spectral Images

In the field of precision agriculture research, it is very important to monitor crop growth in time so as to effectively conduct field diagnosis and management and accurately predict yield and quality. In this experiment, the relationship between the vegetation index of Zhengdan 958 and Suyu 41 and their yield and quality when reducing N application (25 and 50% N reduction compared to local conventional N application rate) under low, medium and high planting densities (60,000, 75,000 and 90,000 plants·ha−1) during 2018–2020 was investigated using multispectral images obtained from UAV monitoring. The results showed that under different density treatments, the normalized vegetation index (NDVI) and ratio vegetation index (RVI) decreased with the decrease in nitrogen application, while the plant senescence reflectance index (PSRI) increased. Through principal component analysis (PCA) and subordinate function analysis, the comprehensive score of each treatment can reflect the maize yield and total protein content under each treatment. Based on the vegetation index, predictive models of maize yield and protein content were established. The best prediction period for grain yield and protein content were physiological maturity and 35 days after silking (R4), respectively. The R2 of the predictive models are greater than 0.734 and 0.769, respectively. Multi-period and multi-vegetation indexes can better monitor crop growth and help agricultural field management.

Functional Mapping of Genes Modulating Plant Shade Avoidance Using Leaf Traits.

Shade avoidance syndrome (SAS) refers to a set of plant responses that increases light capture in dense stands. This process is crucial for plants in natural and agricultural environments as they compete for resources and avoid suboptimal conditions. Although the molecular, biochemical, and physiological mechanisms underlying the SAS response have been extensively studied, the genetic basis of developmental variation in leaves in regard to leaf area, petiole length, and leaf length (i.e., their allometric relationships) remains unresolved. In this study, with the recombinant inbred line (RIL) population, the developmental traits of leaves of Arabidopsis were investigated under two growth density conditions (high- and low-density plantings). The observed changes were then reconstructed digitally, and their allometric relationships were modelled. Taking the genome-wide association analysis, the SNP genotype and the dynamic phenotype of the leaf from both densities were combined to explore the allometry QTLs. Under different densities, leaf change phenotype was analyzed from two core ecological scenarios: (i) the allometric change of the leaf area with leaf length, and (ii) the change of the leaf length with petiole length. QTLs modulating these two scenarios were characterized as 'leaf shape QTLs' and 'leaf position QTLs'. With functional mapping, results showed a total of 30 and 24 significant SNPs for shapeQTLs and positionQTLs, respectively. By annotation, immune pathway genes, photosensory receptor genes, and phytohormone genes were identified to be involved in the SAS response. Interestingly, genes modulating the immune pathway and salt tolerance, i.e., systemic acquired resistance (SAR) regulatory proteins (MININ-1-related) and salt tolerance homologs (STH), were reported to mediate the SAS response. By dissecting and comparing QTL effects from low- and high-density conditions, our results elucidate the genetic control of leaf formation in the context of the SAS response. The mechanism with leaf development × density interaction can further aid the development of density-tolerant crop varieties for agricultural practices.

Effect of Different Soil Types and Plant Densities on Growth Dynamic and Yield of Sweet Corn (Zea mays L.) in Peninsular Malaysia

Aims: Soils and plant densities are two of the major factors affecting sweet corn growth and yield. Although many worldwide studies were done to evaluate the effect of these factors on sweet corn, it is still necessary to do more study in this area because environmental factors will give significant effect to growth and yield of sweet corn. The objective of this study is to assess yield optimization through different plant densities for different type of soils for sweet corn (Zea mays L.) cultivation.
 Study Design: The experiment was carried out from February to May 2018 using split-split plot design with four replications. Analysis of Variance (ANOVA) with probability value of @ 0.05 using LSD was used to analyze the obtained data. Regression analyses were performed using Nonlinear Regression Model (NLIN Procedure); Logistic Growth Model y=A/(1+be-cx) and their rate of change was calculated using its derivate, dy/dx = (Abce-cx)/(1+be-cx)2.
 Methodology: A variety of sweet corn seed Akik SC422 at (i) four soils which were riverine soil (Tanah Merah, Kelantan), BRIS (Bachok, Kelantan), peat (Simpang Renggam, Johor) and sedentary soil (UPM, Serdang, Selangor) assigned as the main plots with (ii) 1 and 2 row(s) per bed plant arrangements as subplots at (iii) 25 cm and 50 cm planting distances formed as sub-subplots.
 Results: Interaction between peat at 2-row per bed plant arrangement at 25 cm planting distance produced the highest potential plant height while peat at 1-row per bed plant arrangement at 50 cm planting distance the best in highest potential in stem diameter. The interaction between peat with 1-row per bed plant arrangement at 50 cm planting distance; low plant density produced the highest in cob weight, cob length, cob diameter, thousand kernel’s weight and total sugar content. This was reflected by higher growth rates of photosynthesis rate, leaf area per plant and relative chlorophyll content of each individually plant. However, the interaction between peat with 2-row per bed plant arrangement at 25 cm planting distance; high plant density produced the highest in quantity per hectare.
 Conclusion: Results of this study confirms that significant differences in the plant growth, physiological attributes and yield components of sweet corn grown on different soil types, plant arrangements and planting distances.

Dominant tree selection for height estimation and its impact on site classification for African mahogany stands

African mahogany plantations are increasing in Brazil, especially those planted with the species Khaya grandifoliola C. DC. Despite the interest in establishing plantations, there is a lack of studies in management practices for the genus. This makes it difficult to improve methodologies that optimise forest inventory activities, which are essential to support forest management decisions. Therefore, this study aimed to evaluate the effect of the number of trees selected to determine the mean dominant height, and to verify its impact on site classification of African mahogany stands. This will then optimise height sampling and ensure correct site index estimation. To determine the dominant height, 11 treatments were tested, with the selection of 1st to 11th thickest trees per plot, representing between 9 and 102 dominant trees per hectare. The effect of the treatments was evaluated using the values of the mean dominant height and metrics regarding site index classification (stability, stratification capacity and relationship with stand growth). Treatments with inclusion of more dominant trees resulted in a more stable site classification at the expense of a lower correlation with stand growth. Treatments using fewer dominant trees resulted in a greater allocation of plots in the upper site classes, showing that the number of trees used to calculate the dominant height influences the distribution of plots in different site classes. We concluded that Treatments 3 (27 trees ha−1) to 6 (55 trees ha−1) had the best performance, guaranteeing adequate site index estimation. The selection of at least 27 and a maximum of 55 dominant trees per hectare is recommended for African mahogany plantations with low planting densities.

Plant density influences yield, yield components, lint quality and seed oil content of cotton genotypes

Choosing suitable varieties and manipulating plant population are crucial management aspects in any cropping system that goals to improve yield, quality and the balance between plant demand and environmental resource availability. A two-year field experiment was conducted at Tehran, Iran, in a split plot design and replicated thrice to examine the effect of the planting density (low, moderate and high) on ten cotton genotypes. In term of lint yield and among the cotton genotypes G8 (1269 kg · ha−1), G4 (1263 kg · ha−1), G1 (1239 kg · ha−1) and G2 (1123 kg · ha−1) were statistically at par with each other but significantly superior to G7 (914 kg · ha−1) and G9 (936 kg · ha−1). Lint yield in high plant density (1386 kg · ha−1) was found to be remarkably superior over medium and low plant density (1029 and 890 kg · ha−1, respectively) by average of 25.7% and 35.7%, respectively. Cotton genotypes at low plant density had higher boll plant−1 (6.46% and 15.3%, respectively), lint percentage (5.8% and 12%, respectively) and lint strength (0.6% and 1.9%, respectively) compared to moderate and high plant densities. The genotypes cultivated at high plant density produced higher seed and lint yield, higher lint elasticity and lower seed oil content, lint length and lint quality index. Based on this experiment, it is concluded that high seed cotton yield can be achieved at high plant density while higher lint quality can be yielded at low plant density.

Sorghum growth influenced by cultivar, nitrogen fertilizer rate and plant density under different environmental conditions

This study aimed to determine the effect of cultivar, nitrogen fertilizer rate and plant density on sorghum growth performance under different environmental conditions. A field experiment was carried out at two different locations of North-West province during 2016/17 and 2017/18 planting seasons. The experiment was laid out as a split split plot arrangement fitted into a randomized complete block design with four replications. The main plot factors were higher plant density (33 333 plants/ha) and lower plant density (22 222 plants/ha). The subplot factors consisted of nitrogen fertilizer rates of 0, 100 and 150 kg/ha. The sub-sub plot factors included two sorghum cultivars, PAN 8625 and PAN 8816. The measured growth parameters were plant height, stem diameter, leaves per plant, leaf chlorophyll content and leaf area index. Sorghum fertilised with 100 kg N/ha had a significantly taller plant of 94.07 cm than sorghum fertilised with 0 and 150 kg N/ha at 51 DAP. During 2016/17 planting season, sorghum cultivar PAN 8625 had a significantly higher number of 13.29 leaves than PAN 8816 at 51 DAP. Sorghum cultivar PAN 8625 also had a significantly higher number of 12.71 leaves than PAN 8816 at 74 DAP. Sorghum growth was enhanced by application of 100 kg N/ha. In this study, sorghum cultivar PAN 8625 is recommended to farmers due to its superior growth performance.

Effects of Nitrogen Application Rate and Plant Density on Severity of Tar Spot of Corn

Tar spot of corn, caused by the fungus Phyllachora maydis, is an economically important foliar disease recently reported in the United States and Canada. Due to the recent introduction of Phyllachora maydis, the impacts of cultural management practices on disease development are still unknown. Separate field studies were conducted to determine the effects of nitrogen (N) application rate and plant density on disease development. Field trials were conducted across six site years in Michigan with two corn hybrids of differing disease susceptibility. The relative area under the disease progress curve was used to compare disease development between N application rates and plant densities. Nitrogen application rate had no significant effect on disease at any location. Plant density and disease had a significant ( P < 0.05) inverse relationship at five of six site years, with an average 41% decrease in the relative area under the disease progress curve for every 1,000 plants per hectare increase. The economically optimal planting density ranged from 73 to 77 thousand plants per hectare for US$150 to 300 per metric ton corn prices, demonstrating that relatively low planting densities were more profitable despite greater disease. Therefore, other disease management practices including hybrid selection may be more effective at protecting yield than increasing plant density.

不同生态调控情景下人工林可持续经营收益研究

PDF HTML阅读 XML下载 导出引用 引用提醒 不同生态调控情景下人工林可持续经营收益研究 DOI: 10.5846/stxb202206291848 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(71803180);国家社会科学基金项目(22BGL168);教育部人文社科青年基金项目(18YJCZH140);浙江省软科学研究计划项目(2023C35077) Research on sustainable management benefits of plantation under different ecological regulation scenarios Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在林业碳汇项目设计与作业标准基础上,将中国东北地区典型人工林生长与经营相关多源数据融合,运用系统动力学理论与方法,构建人工林生态经济系统模型,通过设计实施主伐/间伐、营造混交林、补植补造等不同生态调控情景,模拟并预测人工林可持续经营的生态-经济收益,以此掌握人工林生态调控机制,并为人工林可持续经营决策提供参考。模拟结果显示:①高初植密度能有效增汇,而低初植密度相比基准情景则减少了碳汇;②高主伐率使得木材收益大幅提升,而无主伐限制了木材收益,且从长期来看碳汇收益有限;③高密度-无主伐情景下的累计碳汇量最大,高密度-高主伐情景下的木材收益净现值和总收益净现值最大;若以可持续经营为目标,平衡生态收益和经济收益,则高密度-高主伐情景为理想选择,该情景的累计碳汇量相比高密度-无主伐情景损失有限,对应碳汇收益净现值为357.9万元,以5%贴现率计算的木材总收益和累计总收益的净现值分别为1219.35万元和1577.25万元。由此证实了以林业碳汇项目为依托,因地制宜地构建将造林、抚育、采伐、再造林更新于一体的人工林可持续经营项目,平衡发挥森林生态系统的综合功能,可纾解因无法采伐所带来的高额机会成本,在增汇的同时获得更大的木材收益。适度提高造林密度或造林面积可以增汇,但碳汇收益还取决于碳定价;此外,合理采伐也是实现人工林可持续经营的方式之一,可持续经营收益的关键在于科学的生态调控机制;应向平衡生态与经济收益的目标转变,加快林业经营理念转变与相关法律体系制定。 Abstract:Based on the design and operation standards of forestry carbon sequestration project, the multi-source data related to the growth and management of typical plantations in Northeast China are integrated, and the ecological and economic system model of plantations is constructed by using the theory and method of system dynamics. The ecological and economic benefits of sustainable management of plantations are simulated and predicted through the design and implementation of different ecological regulation scenarios such as main felling/thinning, creation of mixed forests, replanting to master the ecological regulation mechanism and provide reference for sustainable management decision of plantations. The simulation results show that: ① high initial planting density can effectively increase the carbon sequestration, while low initial planting density can reduce the carbon sequestration compared with the baseline scenario; ② High main cutting rate has greatly increased the timber benefits, while no main cutting has limited the timber benefits, and the carbon-sequestration benefits are limited in the long run; ③ The cumulative carbon sequestration of plantation is the largest under the scenario of high density and no main cutting, and the net present value of timber benefits and the net present value of total benefits of plantation are the largest under the scenario of high density and high main cutting. If we take sustainable management as the goal, balance ecological and economic benefits, and take the high density and high main cutting scenario as the optimal choice, the loss of the cumulative carbon sequestration is limited in this scenario compared with the high density and no main cutting scenario. The corresponding net present value of carbon-sequestration benefits is 3.579 million yuan, and the net present value of total timber benefits and cumulative total benefits at a discount rate of 5% are 12.1935 million yuan and 15.7725 million, respectively. It is confirmed that the sustainable management project of plantations integrating afforestation, tending, cutting, reforestation and regeneration based on the forestry carbon sequestration project can be built according to local conditions, and the comprehensive function of forest ecosystem can be balanced. It can relieve the high opportunity cost caused by the inability to cut, and obtain greater timber benefits while increasing carbon sequestration. Moderate increase of afforestation density or afforestation area can increase carbon sequestration, but the benefits of carbon sequestration also depend on carbon pricing. In addition, rational cutting is also one of the ways to achieve sustainable management of plantation; the key to sustainable management benefits lies in scientific ecological regulation mechanism. We should change to the goal of balancing ecological and economic benefits, accelerate the transformation of forestry management concept and the formulation of relevant legal system. 参考文献 相似文献 引证文献

Agronomic parameters of sugarcane under planting densities in different cultivation cycles.

Low density sugarcane plantation (LDSP) has been implemented by some sugarcane producers in Brazil, aiming to save seeds and operational costs. The study was carried out in the municipality of Areia, Paraíba, Brazil. Five planting densities were used, varying from 5 to 25 m-2 of buds arranged in randomized blocks, with four replications. Data were measured annually over three cultivation cycles (2017 to 2020), during which the field was fertilized with NPK and the harvests were carried out manually without prior burning. The lower planting density presents higher productivity only in the cane plant (101.03 t ha-1) due to the higher plant height (2.37 m) and the higher number of stalks (11 stalks m-2), suggesting that these variables are due to the greater availability of light, water and photosynthate. However, there is a drastic reduction in sugarcane yield for this lower population in the 2nd ratoon by up to 65.62%, which is correlated with number of stalks per meter. We demonstrate the agronomic viability of LDSP in the population of 10 buds m-2 in relation to conventional planting of sugarcane until the 2nd ratoon. Data are important for future studies to present additional considerations for other production factors, such as the effects of mechanized harvesting and the management of nutrients and water, assessing the sustainability of this large-scale planting system.

Plant population density in cotton: Addressing knowledge gaps in stand uniformity and lint quality under dryland and irrigated conditions

A recent literature review and data synthesis better defined the yield curve with plant population density in cotton (Gossypium hirsutum L.), but it also highlighted gaps in knowledge. Few cotton plant population studies have been conducted in relatively low-yielding dryland conditions; fewer have considered the impact of uneven crop stands, which are common in actual field conditions due to planting equipment errors and seed/plant mortality; and population reports that include fiber quality measurements by Advanced Fiber Information System (AFIS) testing are lacking (rather than just the standard High Volume Instrument (HVI) measurements). To address these issues, a study was conducted in North Texas, USA with treatment combinations of two irrigation levels (0% and 90% ET replacement), five plant population densities (15,000, 30,000, 60,000, 90,000, and 120,000 plants ha-1), and two stand uniformities (even and uneven plant-to-plant spacing within rows). Canopy development was tracked by unmanned aircraft system (UAS) measurements, late-season measurements were taken of boll density and size, and lint yield and quality measurements were collected at maturity. Lint yield was unaffected by plant population density in 2020 (i.e. 15,000–120,000 plants ha-1), whereas an interaction between irrigation and plant population occurred in 2021. Lint yield was reduced by 19% with 15,000 plants ha-1 relative to 120,000 plants ha-1 under only irrigated conditions in 2021. There was no substantial or consistent effect of stand uniformity on any response variable in either year. Poor stand quality is often the basis for terminating and replanting or replacing troubled cotton crops, but these results suggest this is not justified when overall population density is 30,000 plants ha-1 or greater, depending on production environment. The risk of yield loss is clearly greater when overall plant density decreases below this level, especially in higher-yielding conditions, but the economic tradeoffs of replanting or replacing the crop must be considered. In the cotton plant, yield compensation for low plant density and uneven stands occurred primarily by increased boll number per plant and secondarily by increased boll size. Fiber quality parameters as measured by HVI and AFIS were minimally and inconsistently affected by population density and stand uniformity, suggesting that population dynamics are not critical factors cotton producers must consider in optimizing the fiber quality of their product.

Growth and Yield of Stevia (Stevia rebaudiana Bertoni) as Influenced by Plant Density and Pinching

A field experiment was carried out to standardize spacing and pinching time to enhance the yield and quality of stevia (Stevia rebaudiana Bertoni) at the Department of Agronomy, College of Agriculture, Thrissur, Kerala, from September 2021 to May 2022. The design of the experiment was factorial RBD and replicated thrice. The experiment comprised three levels of spacing (15 cm × 10 cm, 20 cm × 10 cm, and 15 cm × 15 cm) and four pinching intervals (pinching at 20 days after planting (DAP), pinching at 30 DAP, pinching at flower bud initiation and no pinching) in all possible combinations. The plants grown with closer spacing (15 cm × 10 cm) were the tallest at all growth stages. The pinching of the apical bud caused a reduction in plant height and increased the number of branches. Pinched plants recorded higher fresh and dry leaf weights than plants left non-pinched. More leaves were registered under the wider (15 cm × 15 cm) spacing than narrower spacings. Pinching favored the formation of more lateral buds, producing a more significant number of branches and, finally, more leaves per plant. High-density planting of stevia yielded the highest aboveground fresh mass (10925 kg ha-1), whereas lower plant densities yielded the lowest aboveground fresh mass (7330 kg ha-1). The stevia planted at a spacing of 15 cm × 10 cm and pinched at flower bud initiation (11980 kg ha-1) produced higher herbage.

Response of Water Radiation Utilization of Summer Maize to Planting Density and Genotypes in the North China Plain

Increasing the planting density of summer maize to improve the utilization efficiency of limited soil and water resources is an effective approach; however, how the leaf water-use efficiency (WUEL), yield, and RUE respond to planting density and genotypes remains unclear. A 2-year field experiment was performed in the North China Plain (NCP) to investigate the effects of planting density (high, 100,000 plants ha−1; medium, 78,000 plants ha−1; and low, 56,000 plants ha−1) and genotypes (Zhengdan 958 and Denghai 605) on the leaf area index (LAI), photosynthetic characteristics, dry-matter accumulation, WUEL, and RUE of maize. The objective was to explore the effect of density and genotype on the WUEL and RUE of maize. Increasing planting density boosted LAI, light interception, dry-matter accumulation, and spike number but reduced the chlorophyll content, net photosynthetic rate, transpiration rate, and 1000-kernel weight. Both high and low planting densities were averse to RUE and yield. Zhengdan 958 increased the WUEL by 19.45% compared with Denghai 605, but the RUE of Denghai 605 was 18.19% higher than Zhengdan 958, suggesting that Denghai 605 had a greater production potential as the planting density increased. Our findings recommend using 78,000 plants ha−1 as the planting density with Denghai 605 to maintain summer maize yields in the NCP.

Crown Lifting of Low-Density Loblolly Pine (Pinus taeda) Plantations on Nonindustrial Private Forest Lands

AbstractPruning or the physical removal of lower branches, in combination with wider tree spacing, offers an alternative management scheme for small nonindustrial private forest landowners in areas lacking markets for small diameter wood. A 5-year-old loblolly pine (Pinus taeda) plantation was thinned to 495 trees/ha (200 trees/ac). Four crown-lifting treatments of 35%, 40%, 45%, and 50% live crown ratio (LCR) were then implemented. An additional unmanaged plot was established in an unthinned, unpruned area. Two replications were established for all pruning treatments. The target LCR was maintained throughout the study with the additional crown-lifting activities in 2003, 2004, and 2008. At age 8, the average diameter of the unmanaged plot was 13.5 cm (5.3 in), and the diameter of the 50% LCR treatment, which had the greatest diameter growth of all the treatments, was 20.8 cm (8.2 in). The highest mortality rate (22%) was observed in the unmanaged plot, but it was not significantly greater than the other treatments. Low density plantings maintained with pruning could allow small nonindustrial private landowners to obtain a high value sawtimber product while eliminating the need for thinning practices commonly used in traditional pine plantation management.

Interactive effects of plant density and nitrogen availability on the biomass production and leaf stoichiometry ofArabidopsis thaliana

AbstractPlant density and nitrogen (N) availability influence plant survival and nutrient use strategies, but the interaction between these two factors for plant growth and the balance of elements remains poorly addressed. Here, we conducted experimental manipulations using Arabidopsis thaliana, with the combination of four levels of plant density and four levels of N addition, and then examined the corresponding changes in plant biomass production (indicated by total plant biomass and biomass partitioning) and nutrient use strategies (indicated by leaf N and phosphorus (P) stoichiometry). The biomass–density relationship was regulated by N availability, with a negative pattern in low N availability but an asymptotic constant final yield pattern at high N availability. Excessive N addition reduced plant growth at low plant density, but this effect was alleviated by increasing plant density. The root to shoot biomass ratio increased with plant density at low N availability, but decreased at high N availability. N availability was more important than plant density in regulating leaf N and P stoichiometry, with the increasing leaf N concentration and decreasing leaf P concentration under increasing N addition, resulting in a negative scaling relationship between these two elemental concentrations. Our results show that N availability and plant density interactively regulate plant biomass production and leaf stoichiometry of A. thaliana, and highlight that the interactive effects of these two factors should be considered when predicting plant growth behaviour under intraspecific competitive environments in the context of nutrient changes.

Higher sowing density of pearl millet increases productivity and water use efficiency in high evaporative demand seasons.

Pearlmillet is themain subsistence crop for smallholder farmers systemswhere it is grown at low plant density. Intensifying pearl millet cultivation could boost productivity although it may have trade-offs. Increasing planting density would indeed increase the leaf area and the related water budget, whereas a denser canopy could create a more favorable canopymicroclimate to the benefit of the water use efficiency (WUE) of the crops. The first aim of this work was to test the yield response of popular pearlmillet varieties to an increased density and to assess possible genotypic variation in this response. The second aim was to measure the water use and the WUE of the crop in different densities. To this end we designed several field and lysimetric experiments To increase the robustness of the results, these trials were carried out in India and Senegal, using two independent sets of genotypes adapted to both sites. In the field, the higher sowing density significantly increased yield in all genotypes when trials were carried out in high evaporative demand conditions. There was no genotype x density interaction in these trials, suggesting no genotypic variation in the response to density increase. The high-density treatment also decreased the vapor pressure deficit (VPD) in the canopies, both in the field and in the lysimeter experiments. In the lysimeter trials, although the higher density treatment increased water use, the resulting increase in biomass was proportionally higher, hence increasingWUE of the crops in all genotypes under high density. The increase in yield under high density was closely related to the increase in WUE, although this link was more tight in the high- than in the low evaporative demand seasons. This confirmed a strong environmental effect on the response to density of all genotypes tested. Although they did not open a scope for breeding density tolerant cultivars, these results highlight the possibility to improve pearl millet yield by increasing the density, targeting specifically areas facing high evaporative demand.

Comparative analysis of farmer practices and high yield experiments: Farmers could get more maize yield from maize-soybean relay intercropping through high density cultivation of maize

Intercropping is a high-yield, resource-efficient planting method. There is a large gap between actual yield and potential yield at farmer's field. Their actual yield of intercropped maize remains unclear under low solar radiation-area, whether this yield can be improved, and if so, what are the underlying mechanism for increasing yield? In the present study, we collected the field management and yield data of intercropping maize by conducting a survey comprising 300 farmer households in 2016-2017. Subsequently, based on surveyed data, we designed an experiment including a high density planting (Dense cultivation and high N fertilization with plough tillage; DC) and normal farmer practice (Common cultivation; CC) to analyze the yield, canopy structure, light interception, photosynthetic parameters, and photosynthetic productivity. Most farmers preferred rotary tillage with a low planting density and N fertilization. Survey data showed that farmer yield ranged between 4-6 Mg ha-1, with highest yield recorded at 10-12 Mg ha-1, suggesting a possibility for yield improvement by improved cropping practices. Results from high density experiment showed that the two-years average yield for DC was 28.8% higher than the CC. Compared to CC, the lower angle between stem and leaf (LA) and higher leaf area index (LAI) in DC resulted in higher light interception in middle canopy and increased the photosynthetic productivity under DC. Moreover, in upper and lower canopies, the average activity of phosphoenolpyruvate (PEP) carboxylase was 70% higher in DC than CC. Briefly, increase in LAI and high Pn improved both light interception and photosynthetic productivity, thereby mediating an increase in the maize yield. Overall, these results indicated that farmer's yields on average can be increased by 2.1 Mg ha-1 by increasing planting density and N fertilization, under plough tillage.

Crop physiological considerations for combining variable-density planting to optimize seed costs and weed suppression

AbstractHigh crop densities are valuable to increase weed suppression, but growers might be reluctant to implement this practice due to increased seed cost. Because it is also possible to lower planting densities in areas with no or low weed interference risk, the area allocated to each planting density must be optimized considering seed cost and productivity per plant. In this study, the growth and yield of maize (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.] were characterized in response to low planting densities and arrangements. The results were used to develop a bioeconomic model to optimize the area devoted to high- and low-density plantings to increase weed suppression without increasing seed cost. Physiological differences seen in each crop varied with the densities tested; however, maize was the only crop that had differences in yield (per area) between densities. When a model to optimize low and high planting densities was used, maize and cotton showed the most plasticity in yield per planted seed (g seed−1) and area of low density to compensate for high-density area unit. Maize grown at 75% planting density compared with the high-planting density (200%) increased yield (g seed−1) by 229%, return by 43%, and profit by 79% while decreasing the low-density area needed to compensate for high-density area. Cotton planted at 25% planting density compared with the 200% planting density increased yield (g seed−1) by 1,099%, return by 46%, and profit by 62% while decreasing the low-density area needed to compensate for high-density area. In contrast, the high morphological plasticity of soybean did not translate into changes in area optimization, as soybean maintained return, profit, and a 1:1 ratio for area compensation. This optimization model could allow for the use of variable planting at large scales to increase weed suppression while minimizing costs to producers.

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.