Optimum Plant Density Research Articles

Optimum oil palm planting density in West Africa

This article follows on from an earlier one about the same experiment in 2014. A range of various planting distances (from 7.5 to 9.5 metres) between oil palms was tested using an equilateral triangle design. The current planting density experiment was set up in an oil palm plantation in Nigeria. The climatic conditions are quite stable, with two seasons and around 2000 mm of annual rainfall. The soil is of the desaturated ferralitic type, sandy on the surface, deep and without coarse elements. After twelve years of continual monitoring and extrapolation of the results obtained up to the end of the cycle, we concluded on an optimum planting density of between 143 and 160 oil palms per hectare in a monospecific, equilateral triangle planting design (i.e. a distance of 8.5 to 9 metres between palms). It will take another few years of yield recording to fine-tune the result. For 12-year-old palms, this density range corresponds to a Leaf Area Index of 3.5 to 4, a light interception percentage of 89 to 90 and a foliage overlap percentage of 51 to 68. A thinning treatment was included in the protocol. Thinning at eight years has not led to any advantage after four years.

Effects of Planting Density and Nitrogen Fertilizer Rate on Yield and Yield Related Traits of Maize (Zea mays L.) in Northwestern, Ethiopia

In Ethiopia, different N-levels and planting densities were recommended based on the environmental conditions for maize production. However, the optimum nitrogen (N) requirements and planting density have not been yet well determined in the study area. A field experiment was conducted to determine N rate and planting density on maize yield in South Achefer district during 2014 cropping season at 3 locations. Three planting densities and four N levels were tested in randomized complete block design in the factorial arrangement with three replications. There were significant differences (P<0.05) among panting densities. Plant height, ear height, and leaf area index were significantly increased with increasing planting density from 44444 to 88888 plants ha-1. However, the cob diameters, cob length, numbers of kernels per cob were decreased with increasing plating density. The grain yield was increased by 65.16% on 88888 plants ha-1 with 161 kg N ha-1 as compared to 44444 plants ha-1 with 92 kg N ha-1 and it was the best economically (39746.9 birrrs) profitable treatment combination. Thus, it can be concluded that application of 88888 plants ha-1 with 161 kg N ha-1 was found to be superior both agronomical and economically for maize production in the study area.

Breeding Sorghum Using Induced Mutations: Future Prospect for Namibia

In arid and semi-arid regions of the world sorghum stands out as a climate change-ready crop with high potential for the production of food, feed, fodder, fiber and fuel in the face of increasing human population. The present review highlights induced mutation breeding technique as a potential tool for improving sorghum in Namibia. The review discussed the following issues; crop improvement using mutagens, mutant screening, selection and evaluation, impact of induced mutation breeding, factors for declining production and future implication of sorghum mutation breeding. In Namibia, severe drought stress resulting in total crop failure has become frequent. This is partly a consequence of farmers growing crop varieties which cannot withstand impact of drought. As such Namibia has limited drought tolerant varieties available for the diverse agro-ecologies. Farmers keep growing the familiar landraces which performs well in good rainfall years but fails to produce stable yield with irregular and erratic rainfall. Thus, breeding new sorghum varieties of high yield and quality combined with multiple agronomic traits including pest and disease resistance and high efficiency in nutrient and water use is needed. Induced mutation is one of the breeding methods utilized worldwide to supplement conventional breeding for developing superior varieties with desirable traits in different crops. Development of high yielding, drought tolerant, and dwarf sorghums with early maturity enables effective utilization of available soils moisture and in optimizing plant density for achieving higher yield in farmers’ fields. Recombination breeding through exploitation of natural genetic variability and mutation breeding to reduce the plant height without disturbing agronomic superiority of elite lines is recommended for sorghum improvement in Namibia.

Reproductive Sink of Sweet Corn in Response to Plant Density and Hybrid

Improvements in plant density tolerance have played an essential role in grain corn yield gains for ≈80 years; however, plant density effects on sweet corn biomass allocation to the ear (the reproductive ‘sink’) is poorly quantified. Moreover, optimal plant densities for modern white-kernel shrunken-2 (sh2) hybrids are unknown. The objectives of the study were to 1) quantify the effect of plant density and hybrid on the reproductive sink of sweet corn and 2) determine optimal plant densities for white-kernel sh2 sweet corn. Field experiments were conducted across 2 years on 10 white-kernel sh2 hybrids grown at plant densities ranging from 4.3 to 8.6 plants/m2. Increasing plant density negatively influenced reproductive sink characteristics of individual sweet corn plants, including linear decreases in ear shoots/plant, marketable ears/plant, ear length, filled ear length, ear mass/plant, and kernel mass/plant. Reproductive traits varied widely among hybrids, including ear mass (15.6–20.6 Mt·ha−1) and recovery (32.3% to 42.4%), which is the contribution of fresh kernel mass to total ear mass. Hybrids had a common response to plant density, whereby ear yield was optimized at 5.5 plants/m2 and gross profit margin was optimized at 6.1 plants/m2. Plant density data from 586 growers’ fields suggest current seeding rates have optimized the reproductive sink size for today’s white-kernel sh2 hybrids. However, room exists for improving plant density tolerance, yield, and profitability.

Symbiotic performance of grain and wild herbaceous legumes in the Okavango Delta and Tswapong region of Botswana

The low inherent soil fertility, especially nitrogen (N) constrains arable agriculture in Botswana. Nitrogen is usually added to soil through inorganic fertilizer application. In this study, biological nitrogen fixation by legumes is explored as an alternative source of N. The objectives of this study were to measure levels of N2 fixation by grain legumes such as cowpea, Bambara groundnut and groundnut in farmers’ fields as well as to estimated N2 fixation by indigenous herbaceous legumes growing in the Okavango Delta. Four flowering plants per species were sampled from the panhandle part of the Okavango Delta and Tswapong area. Nitrogen fixation was measured using the 15N stable isotope natural abundance technique. The δ15N values of indigenous herbaceous legumes indicated that they fixed N2 (−1.88 to +1.35 ‰) with the lowest value measured in Chamaecrista absus growing in Ngarange (Okavango Delta). The δ15N values of grain legumes growing on farmers’ fields ranging from −1.2 ‰ to +3.3 ‰ indicated that they were fixing N2. For grain legumes growing at most farms, %Ndfa were above 50% indicating that they largely depended on symbiotic fixation for their N nutrition. With optimal planting density, Bambara groundnuts on farmers’ fields could potentially fix over 90 kg N/ha in some parts of Tswapong area and about 60 kg N/ha in areas around the Okavango Delta. Results from this study have shown that herbaceous indigenous legumes and cultivated legumes play an important role in the cycling of N in the soil. It has also been shown that biological N2 on farmer’s field could potentially supply the much needed N for the legumes and the subsequent cereal crops if plant densities are optimized with the potential to increase food security and mitigate climate change.

Effect of Plant Density on Sweet and Biomass Sorghum Production on Semiarid Marginal Land

Plant density substantially affects sorghum (Sorghum bicolor (L.) Moench) productivity. Therefore, density optimisation plays a pivotal role in crop management practices. A 2-year field experiment was conducted on sandy loam marginal land in Ordos, Inner Mongolia, China, to (1) determine the mechanism underlying the impact of plant density (i.e. 6.0, 7.5, 9.0, 10.5 and 12.0 plant m−2) on biomass yield, quality and photosynthetic efficiency and (2) determine the optimum plant density for sweet sorghum variety GT-3 and biomass sorghum variety GN-4. Results indicate that plant height, leaf area index (LAI), leaf area duration (LAD) and biomass yield increased as plant density increased, but tiller number, stem diameter and net assimilation rate (NAR) decreased. The growth period between elongation and anthesis dates was crucial to sorghum productivity; during this period, LAD was the determining factor for biomass yield. Increase in plant density up to 10.5 plant m−2 led to a high LAI level, an extended LAD, a high and stable NAR and a positive balance between photosynthesis and respiration processes, all of which contributed to highest biomass yield (13.2 t ha−1). Ultimately, sweet-type variety GT-3 demonstrated the highest theoretical ethanol yield (4147 L ha−1) and relative feed value (112.3%) compared with biomass-type variety GN-4.

Plant growth regulator and its interactions with environment and genotype affect maize optimal plant density and yield

Abstract Increasing planting density is important to raise maize yield, however, high density often leads to an increase risk of lodging due to dense canopy and weak stem. Maize yield and optimal plant density are increased by applying plant growth regulator compound of ethephon and DA-6, however, we do not know if this compound would interact with location and genotype. In this study, a novel plant growth regulator, as the synthesis of N, N- diethyl − 2 − hexanoyl oxygen radicals − ethyl amine (2-ethyl chloride) phosphonic acid salt (DHEAP), combining the effects of ethephon and DA-6 in one chemical, was developed and tested at three locations, five plant densities (6.75, 8.25, 9.75, 11.25 and 12.75 plants m−2) and three cultivars in 2014–2015. This study aimed to quantify the interactions between environment, genotype and management (Appling DHEAP and plant density) on lodging-related optimal plant density and yield. DHEAP significantly increased grain yield by 10.7% due to the increases of kernel weight by 3.2% and kernel number per ear by 4.4%. On average across genotypes and environments, applying DHEAP increased optimum plant density by 6%. The optimal plant density interacted with cultivar, DHEAP and environment. Applying DHEAP reduced lodging percentage by lowering ear height. The yield-lodging relationship was affected by genotype and location. We concluded that maize yield could be enhanced by optimizing plant density, applying DHEAP and cultivar selection, but climatic and environmental differences of locations should be considered.

Optimal planting density and sowing date can improve cotton yield by maintaining reproductive organ biomass and enhancing potassium uptake

Cotton is the fifth major oil crop and grown primarily for natural fiber globally. Suitable management practices like planting density (PD) and sowing date (SD) are the major drivers of cotton crop productivity. Cotton production with a normal practice of 3 plants m−2 in Yangtze River Valley China, resulting in an average yield of 1200kgha−1 although, high input costs and low productivity are the two major consequences in cotton production systems. The production costs can be decreased and profits can be increased through optimal PD and adjusting SD. The objectives of this study were to optimize growth, yield, biomass partitioning and potassium (K) distribution of a cotton crop under a short growing season and elevated PD. Experiments were conducted with two sowing dates i.e. early (S1, May 20 and late S2, June 04) as the main plot and three plant densities (D1, low 7.5; D2, moderate; 9.0 and D3, high; 10.5plantsm−2) as the subplot laid out in a split arrangement with four replicates. D3 crops significantly delayed cotton growth period under late sowing date compared with early planted crops. Compared with S2 crops, S1 plants produced 29% and 26% higher seed cotton and lint yield, respectively. Among the PD, D2 plants produced 12%, 15%, 13% and 6% more seed cotton yield and lint yield over D1 and D3 crops respectively. The increment in yield was due to increased plant reproductive organs biomass occasioned by moderate density and longer cropping season which allowed the utilization of available resources. Higher K acquisition i.e. (0.9VMkgha−1d−1), further improved reproductive structures formation in S1 combined with D2 crops. The S1 in combination with D2 crops resulted in the highest average (77VTkgha−1d−1) and maximum (93VMkgha−1d−1) rates of reproductive organs biomass accumulation than other combinations. Conclusively, use of medium density under both sowing dates is an effective strategy for optimal seed cotton and lint yield.

Effects of Seeding Rate on Durum Crop Production and Physiological Responses

Core Ideas Optimum seeding rate on elite durum wheat depends on environment. Seeding rate had a significant positive relationship with grain yield, leaf area index, and carbon isotope discrimination. Seeding rate should be adjusted for environment and genotype for maximum yield. Seeding rate can be manipulated to optimize the ability of the crop to capture available resources and therefore increase yield. Seeding rate may vary between regions according to the climate conditions, soil type, sowing time, and other agronomic practices. Insufficient information is available for optimum seeding rate on durum wheat (Triticum turgidum L. var durum) for some production zones, and response to seeding rate is unknown for recently registered durum cultivars in Canada. The objective of this study was to determine the effect of seeding rate (SR) on performance of Canada Western Amber Durum wheat cultivars and study the underlying physiological response to a wide range of SRs. Eight durum wheat cultivars were sown at densities of 163, 217, 272, 326, and 380 seeds m−2 to study the effect of SR on several agronomic and physiological traits. Each experiment was planted as a factorial randomized complete block design with three replications near Swift Current and Regina in 2010 and 2011. High genetic and environmental response to SR was observed between cultivars. The results showed an increase in grain yield as the SR increased. The optimum SR for cultivars grown at Swift Current and Regina was 272 to 326 seeds m−2 and 217 to 272 seeds m−2. Grain yield showed a positive relationship with carbon isotope discrimination (CID) and leaf area index (LAI). In turn, LAI showed a linear increase with SR. Information generated from this study could enable producers to maximize crop grain profitability by optimizing plant density.

Agronomic management of CRIDA-18R- a new variety of horse gram (Macrotyloma uniflorum) for South India matching monsoon patterns of rainfall

A rainfed experiment was conducted at two contrasting rainfall situations of two different states of South India viz., Hyderabad (Telangana) and Tirupathi (Andhra Pradesh) during 2007-08 to standardize the optimum sowing time, plant densities and fertiliser dose for horsegram variety CRIDA 18R released and recommended for cultivation in South India. Results showed that the second fortnight of August and first fortnight of November were suitable optimum times of sowing in Hyderabad and Tirupathi regions respectively due to receipt of rainfall from South West monsoon and North East monsoon at respective locations. Plant densities of 3.33 lakh per hectare with or without 10N + 20P2O5 fertilizer dose yielded higher seed in both the regions. However when the sowing was delayed, wisest decision might be to continue the plant densities of 3.33 lakh population per hectare with or without fertilizer. The results revealed that CRIDA-18R responded to fertilizer up to 10 N +20 P2O5 kg ha-1 with 3.33 lakh plant density but for the varied optimum time of sowing at two different centers with occurrence of favourable rainfall situations, revealing a very flexible sowing time for CRHG-18R in South India.

Adjusting maize plant density to different climatic conditions across a large longitudinal distance in China

Climatic conditions, including temperature range and solar radiation, are closely linked to maize (Zea mays L.) growth and development. Adjusting plant density is one of the most effective measures for maximizing maize yield under different climatic conditions. The objectives of this study were (1) to determine the optimum plant density as well as the corresponding leaf area index (LAI) and yield in different maize producing regions in China and (2) to learn how climatic conditions influence maize growth and grain yield. The 3-year (2013–2015) field experiment used a hybrid maize cultivar (‘Zhengdan 958’) with six plant density treatments: 4.5, 6, 7.5, 9, 10.5, and 12plantsm−2. Three different ecological regions were chosen for the study: Gongzhuling (Jilin Province, China), Yinchuan (Ningxia Hui Autonomous Region, China), and Qitai (Xinjiang Uygur Autonomous Region, China). Comparing the same plant density treatment at different sites, grain yield and dry matter accumulation decreased in the order Qitai>Yinchuan>Gongzhuling. The optimum plant densities (i.e., treatments with greatest yield) were 12plantsm−2 at Qitai, 10.5plantsm−2 at Yinchuan, and 7.5plantsm−2 at Gongzhuling. At the optimum plant density, the LAIs at silking and physiological maturity were, respectively, 8.94 and 4.27 at Qitai, 7.50 and 1.85 at Yinchuan, and 6.18 and 1.67 at Gongzhuling. Climatic factors, especially solar radiation and diurnal temperature range, exerted significant influences on maize yield. These observations will be useful for determining best management practices for maize production under different climatic conditions across large areas and for providing helpful suggestions for maize breeders.

Effect of plant density on growth and yield in Barraganete plantain (Musa paradisiaca (L.) AAB cv. Curare enano) for a single harvest cutting in Provincia de Los Ríos, Ecuador

The optimum plant density in Barraganete plantain (Musa paradisiaca (L.) AAB cv. Curare enano) was determined in Los Angeles-Provincia de Los Ríos, Ecuador. Treatments (sowing distance: T1 = 3m x 4m, T2 = 3m x 3m, T3 = 3m x 2m, T4 = 3m x 1.5m and T5 = 3m x 1m), were evaluated in a randomized complete block design with five treatments and three replicates per treatment. The number of hands per cluster, hand weight, weeks to flowering, weeks to harvest, production for export and weed incidence in plantain crop, were evaluated. Variance analysis was performed and means were submitted to the Tukey test at 5% probability (p = 0.05). The optimum sowing distance was 2m between plants and 3m between rows. The best density was 1666 plants. ha-1 and obtained the best average hand weight (14.5 kg), the best average number of hands (4.9), the best average in weeks to harvest after flowering (12.1 Weeks) and the best production (kg.ha-1) of export bunches (close to 22 t.ha-1). Analysis with logistic models show the higher densities, which present advantages in their use, fact related to the increase of the annual plantain production. For this reason, values between 2150 and 2500 plants.ha-1 are postulated as optimal densities. Weed decreases with increasing plant density to a minimum of 227.94 g.m-2 in the highest plant density treatment.

Manipulation of shade and plant density for enhanced production of cut-foliage in Ruscus hypophyllum L.

Cut foliage are deep green with long lasting and evergreen properties which are commonly preferred by the floral industry as accents in floral arrangements. Ruscus hypophyllum L. is one of the commercially produced cut foliage material for making good line, filler and mass material in making floral arrangements. It requires shade for growth. Experiments were conducted with the objectives to find out optimum shade levels and planting density. The rhizomes were planted in factonal randomized block design under three shade levels ( 0, 50% and 75%) and three plant spacing (30x30 cm, 30x40 cm, 30x50cm) with planting density of 18, 15, and 12 plants per m2, respectively. It was observed that different shade levels and plant spacings exhibited significant effect on plant height, stem diameter, number of leaves, leaf size and number of stems harvested per plant. The plants were recorded tallest under 75 % shade levels and 30x30 cm plant spacing (61.30cm and 54.48 cm, respectively). The number of leaves produced per plant were maximum (69.99) under 75% shade, however, number of leaves per plant were maximum under 30x30cm spacing. Among various shade levels, 75% shade level resulted in maximum number of cut stems (16.28) that was at par with 50% shade level (16.08). However, the cut stems harvested per plant were recorded maximum (16.67) under 30x30cm spacing. From the results obtained, it was concluded that Ruscus hypophyllum grown under 75% shade level with 30x30 cm spacing and planting density of 18 plants per m2, produced maximum yield of cut stems with longer stem length.

English

The effects of plant density on yield and yield components in upland rice cultivation were examined by conducting a series of field experiments in Central Uganda, using three African and one Japanese improved upland rice varieties. The estimation of plant-density response functions with respect to yield components and yield revealed that an increase in plant density significantly decreased the number of panicles per hill, number of spikelets per panicle, and 1000-grain weight, and significantly increased the number of panicles per square meter. The percentage of filled grain was not affected by plant density. Compared to the Japanese variety, the three African varieties were characterized by more numbers of panicles/hill, less numbers of spikelets/panicle, higher grain-filling ratio and lighter 1000-grain weight, but differences in the degrees of response to plant density were less distinct between them. Rice yield increased in the range of plant density tested, though the marginal increase in yield due to an increase in plant density by 1 hill/m2 diminished from 100 kg/ha at the plant density of 11 hills/m2 to 30 kg/ha at 33 hills/m2. No significant differences were found among the four varieties for the level of yield as well as for its degree of positive response to plant density. The yield components that determined the increase in yield were the number of panicles per square meter and the number of spikelets per panicle, or combined together, the number of spikelets per square meter, which was estimated to reach the maximum at the plant density of 35 hills/m2. When the differences among the treatments in the costs of seeds and weed-control were considered, the optimum plant density was found to be 22 hills/m2 (plant-spacing of 30 cm × 15 cm), lower than the plant density that gives the maximum yield. Key words: Economic optimum, maximum yield, NERICA, plant-density response function, yield components.

Performance of Miscanthus x giganteus (Greef et Deu) established with plastic mulch and grown from a range of rhizomes sizes and densities in a cool temperate climate

The effect of biodegradable plastic mulch, rhizome size and planting density on establishment, annual harvested biomass yield of miscanthus and nutrient content were studied at two sites in Northern Ireland. In a split plot experimental design plastic mulch treatment was applied randomly to main plots (covered or left uncovered) after planting rhizome fragments varying in size (by weight) and planting density which were assigned randomly to subplots in four replicated blocks, at each site.Mean shoot density over both sites was 7.8 and 12.6m−2 for unmulched and mulched in October of the establishment year. Averaged over all sites and planting treatments, uncovered total biomass yields were 0.47, 4.79, 7.74 and 8.12tDMha−1, for the first four annual spring harvests, respectively, mulch increasing these yields by 68, 49, 36 and 24%, respectively. Although there were significant effects of rhizome size and density, the effect of plastic declined at successive harvests for large and medium sized rhizomes and high and standard densities. The main effect of plastic mulch was to increase the shoot population density, and shoot number per plant, especially in plants from rhizomes planted at a low number per unit area. Although there were soil moisture deficits in some months, mulching was considered to have improved yields mainly by increasing shoot density due to higher soil temperatures during establishment followed by a mild winter. By the third year, plastic mulch had no significant effect on recommended planting density at all harvests. Plastic mulch had no marked effect on content of N, P or K in biomass.Covering miscanthus rhizomes with a biodegradable plastic mulch is an effective management tool to increase miscanthus biomass production in a cool temperate climate, at least in the first 3–4 years of production. This is mainly due to increase in soil temperature during establishment and the subsequent year. Mulching allows the optimum planting density of rhizomes to be reduced. Despite additional cost plastic mulch represents an economic benefit to the crop.

Sustainable management of chickpea pod borer. A review

The pod borer [Helicoverpa armigera Hubner (Lepidoptera: Noctuidae)] is responsible for causing up to 90% damage in chickpea due to its regular occurrence from the vegetative growth to the pod formation stage. In order to manage this problem, growers are tempted to increase the amounts of pesticides, but indiscriminate or injudicious use of pesticides has resulted in residues in the food chain, pesticide resistance, and pest resurgence, in addition to causing harm to non-targeted beneficial organisms and the environment. Here, we reviewed the sustainable approaches to reduce the incidence of pod borer and achieve sustainability in chickpea production systems through the adoption of an integrated approach involving host plant resistance, good agronomic practices, and judicious use of chemical and biological methods. We found that the following major points have been reported to reduce the survival and damage of pod borer: (1) use of resistant varieties (the cheapest and the best method of pod borer management); (2) implementing a number of good agronomic practices, such as early sowing with optimum planting density and fertilizer levels, including inter/trap crops (coriander, mustard, linseed, sunflower, sorghum, and marigold) and installing animated bird perches and T-perches at 2 m distance of predatory zones; and (3) monitoring pod borer through pheromone traps (which is also necessary to understand the major factors influencing pest population and to make the pest control program more effective). Integrating all of these approaches with biological control has shown some encouraging results for sustainable pod borer management and has resulted in high chickpea yields. This review highlights examples of successful management approaches from past studies that were implemented in experimental and farmers’ fields. These approaches can be explored as reproducible practices for managing the pest in locations with similar H. armigera concerns. We conclude that an integrated approach is most effective for long-term sustainable management programs.

THE EFFECTS OF ROW SPACING AND PLANT DENSITY ON YIELD AND YIELD COMPONENTS OF PEANUT GROWN AS A DOUBLE CROP IN MEDITERRANEAN ENVIRONMENT IN TURKEY

This study was conducted at the Cukurova University research farm as a double crop in 2013 and 2014 in Adana, Turkey. The objective of this study was to determine the effect of row distance and plant density on yield and yield components of peanut(Arachis hypogaea L.) grown as a double crop. The experimental design was a split plot design with three replications. The Halisbey (Virginia type) variety was used as a plant material in this research. The row spacing was arranged 70 and 75 cm, and intra-row spacing of 5,10,15,20 and 25 cm was arranged for different plants population. According to a two-year average, the highest pods weight (97.57g plant-1 and 94.83 g plant-1 ) and pod number (96.4 pods plant-1and 93.5 pods plant-1 ) per plant was obtained from 70 x 25 cm and 75 x 25 cm planting density, respectively. Pod number and pod weight per plant was increased when the plant density was decreased. Pod yield per hectare was increased when the plant density was increased. The highest pod yield (7511.9 kg ha-1 ) was obtained from 75x10 cm and the lowest (5171 kg ha-1 ) from 75x25 planting density according to a two-year average. As a result; optimum planting density was found 75x10 cm for Virginia market type varieties in double crop peanut production.

Optimal plant density and N fertilization to achieve higher seed yield and lower N surplus for winter oilseed rape (Brassica napus L.)

Greater synchrony between populations and individual plants is dependent on the interactions between plant density and nitrogen (N) fertilization and is crucial to achieve food and environment security. A two-factor designed experiment of transplanted winter oilseed rape was conducted in the 2012–2013 and 2013–2014 growing seasons in central China. Five transplanted plant densities and six N rates were used to study the influences of plant density and N fertilizer application rate on seed yield, N uptake and apparent N surplus. Optimal plant density was the prerequisite to obtain high seed yield and the contribution of plant density to seed yield was minor when it exceeded the optimal density. N fertilization offset the compensatory effect between plant density and pods per plant, enhance seed yield further. Seed yield increased linearly with the increase of seed N uptake, however, it did not increase as the non-seed parts (stem+pod wall) N uptake increased when seed yield exceeded the critical values in the high plant density treatments. Higher plant densities promoted shoot N uptake and reduced soil mineral N residues and apparent N surplus in root zone. Compared with the recommended transplanted density in this region (9.0×104 plant ha−1), the optimal N fertilizer application rate could be cut down with 10.3%–23.7% for the target yield (3000kgha−1) and apparent N surplus would be declined with 41.5%–92.1% when the density suitably increased to 10.0–12.0×104 plant ha−1; On the contrary, when the density was decreased to 7.0–8.0×104 plant ha−1, increasing N fertilization rate with 13.9%–34.8% also could gain the target yield, but the apparent N surplus would increase with 58.1%–148.0%. Consequently, varied combinations between plant densities and N fertilizer application rate are useful to fulfill high seed yield. Reducing N fertilizer rates under suitable higher plant densities are the optimal N management strategy to achieve high yield with lower environment risks.

Yield gaps in oil palm: A quantitative review of contributing factors

Abstract Oil palm, currently the world’s main vegetable oil crop, is characterised by a large productivity and a long life span (≥25 years). Peak oil yields of 12 t ha−1 yr−1 have been achieved in small plantations, and maximum theoretical yields as calculated with simulation models are 18.5 t oil ha−1 yr−1, yet average productivity worldwide has stagnated around 3 t oil ha−1 yr−1. Considering the threat of expansion into valuable rainforests, it is important that the factors underlying these existing yield gaps are understood and, where feasible, addressed. In this review, we present an overview of the available data on yield-determining, yield-limiting, and yield-reducing factors in oil palm; the effects of these factors on yield, as measured in case studies or calculated using computer models; and the underlying plant-physiological mechanisms. We distinguish four production levels: the potential, water-limited, nutrient-limited, and the actual yield. The potential yield over a plantation lifetime is determined by incoming photosynthetically active radiation (PAR), temperature, atmospheric CO2 concentration and planting material, assuming optimum plantation establishment, planting density (120–150 palms per hectares), canopy management (30–60 leaves depending on palm age), pollination, and harvesting. Water-limited yields in environments with water deficits >400 mm year−1 can be less than one-third of the potential yield, depending on additional factors such as temperature, wind speed, soil texture, and soil depth. Nutrient-limited yields of less than 50% of the potential yield have been recorded when nitrogen or potassium were not applied. Actual yields are influenced by yield-reducing factors such as unsuitable ground vegetation, pests, and diseases, and may be close to zero in case of severe infestations. Smallholders face particular constraints such as the use of counterfeit seed and insufficient fertiliser application. Closing yield gaps in existing plantations could increase global production by 15–20 Mt oil yr−1, which would limit the drive for further area expansion at a global scale. To increase yields in existing and future plantations in a sustainable way, all production factors mentioned need to be understood and addressed.

Leaf Senescence, Root Morphology, and Seed Yield of Winter Oilseed Rape (Brassica napus L.) at Varying Plant Densities.

In this study, the yield and yield components were studied using a conventional variety Zhongshuang 11 (ZS 11) and a hybrid variety Zhongyouza 12 (ZYZ 12) at varying plant densities. The increase in plant density led to an initial increase in seed yield and pod numbers per unit area, followed by a decrease. The optimal plant density was 58.5 × 104 plants ha−1 in both ZS 11 and ZYZ 12. The further researches on physiological traits showed a rapid decrease in the green leaf area index (GLAI) and chlorophyll content and a remarkable increase in malondialdehyde content in high plant density (HPD) population than did the low plant density (LPD) population, which indicated the rapid leaf senescence. However, HPD had higher values in terms of pod area index (PAI), pod photosynthesis, and radiation use efficiency (RUE) after peak anthesis. A significantly higher level of dry matter accumulation and nitrogen utilization efficiency were observed, which resulted in higher yield. HPD resulted in a rapid decrease in root morphological parameters (root length, root tips, root surface area, and root volume). These results suggested that increasing the plant density within a certain range was a promising option for high seed yield in winter rapeseed in China.