High Density Planting For Root Shoot Fruit Crops

Plant density may seem like an abstract concept, yet its determination and selection have far-reaching ecological and economic ramifications – particularly within protected structures.

Many woody fruit varieties are grafted onto rootstocks in order to manage tree size and shape as well as improve disease resistance, as well as to achieve high cropping efficiency.

Light

Light plays an integral part in crop growth and development, impacting nutrient uptake as well. Therefore, optimizing lighting environments in horticultural crops to increase yield, quality, and reduce chemical fertilizer usage is of key importance to maximize yield and reduce chemical use; high densities planting is one way of accomplishing this; however, due to its complex impact on uptake of nutrients through light it should be considered carefully when designing lighting environments for these crops.

Planting density recommendations for horticultural crops vary significantly, depending on factors like species, growing system, season length and cultivar selection. Onions require 1.5 inches between rows while large pumpkins require 72 inches between beds. Row and space variations also play a factor.

Understanding how planting density affects nutrient uptake is critical to increasing fruit yield and quality. For instance, increasing density will accelerate tree growth and produce more fruits, though this does not always translate to improved fruit quality; high-density planting can sometimes increase diseases while simultaneously decreasing nutrient uptake.

Planting density also plays a key role in affecting the amount of chlorophyll produced in plant leaves; Nagpur mandarins grown under high density had low chlorophyll content while those at lower planting densities showed higher chlorophyll content. Furthermore, higher planting densities may alter root structures.

Studies conducted on fruit-maize-AF agroforestry systems demonstrated that crop location on slope was more critical for light distribution and performance than planting density, since crops upsloping of fruit trees received more light and intercepted more of it than those downsloping. Furthermore, an increase in flower rate (FR) led to stem elongation among three lettuce cultivars with rosette plant architecture, yet did not influence leaf expansion of cucumber seedlings with upright architecture.

Water

Scientific investigation of roots has lagged behind that of shoots, flowers, and fruits due to the difficulty involved in studying what happens underground. Roots do more than absorb water and nutrients from soil – they send signals telling other parts of a plant about the state of soil in terms of water/nutrient content/hardness/temperature conditions.

Roots perform their signaling role through water availability and soil conditions such as drainage, aeration, soil structure (such as sand or clay) and the presence of humus. When soil conditions are optimal, roots grow rapidly and spread throughout available volume; otherwise their rate of growth and distribution may be limited.

At the first field experiment conducted in winter 2018, periodically excised shoots showed an apparent decline in water content as air temperatures began to exceed 0degC, suggesting atmospheric evaporative demand as the primary driver. This finding corroborated with other studies which have shown similar decreases in shoot water content due to increasing air temperatures during periods when control or high density planting decreased water content levels over time.

One way to control excessive shoot growth in high density plantings is through chemical growth retardants like Regalis or Paclobutrazol. These chemicals work by inhibiting the production of ethylene in leaves, which leads to reduced vigour and rapid growth among young trees. Their usage must be closely monitored as overuse may cause fruit drop; additionally, any reduction should also include appropriate pruning of excess wood for fruitful results.

Fertilization

Fruit crops require regular fertilization as their roots interact directly with the soil and extract significant amounts of essential nutrients like nitrogen (N) and phosphorus (P). Because fertilization has such an impactful impact on yield, it’s wise to fertilize your soil to an appropriate degree prior to planting so as to provide your trees with optimal growth conditions and high productivity rates.

As far as selecting plant density is concerned, studies have demonstrated that closer between-row spacings are more effective at increasing yield of large fruits than within-row spacings. It’s essential that an exact distance is considered; too little could result in reduced crops while too much could mean excessive water and fertilizer use.

A decision on planting density also depends on a range of other considerations, including rootstock type. Rootstock influences tree and crop characteristics like height and fruit weight as well as canopy development and light penetration; in an experiment conducted on “Honeycrisp” trees grown at various densities, medium density planting demonstrated greater height, fruit per tree production and lower yield per hectare than high-density systems.

Researchers also observed that hazelnuts produced in a high-density system had higher protein, fat and NSC content compared to medium density systems, likely as fruiting tends to occur at the middle and upper areas of the canopy. Furthermore, high density planting systems allow more efficient use of aboveground resources as well as allocation of carbon and nitrogen for photosynthesis in canopy photosynthesis.

Pruning

As with any production practice, pruning should be carefully considered in relation to yield and vine capacity. Achieving optimal productivity requires appropriate levels of pruning without excessive investment of land and inputs – especially true for HDPs which increase plant densities per hectare but require intensive management due to interplant competition for light and resources.

The optimal density depends on a number of factors, including plant type and cultivar, site conditions, desired yield/canopy shape/fruit quality objectives, photosynthetic capacity needs (reducing water and fertilizer use), crop quality/pollinator attraction needs/attraction goals as well as biodiversity/carbon sequestration benefits. Planting density increases photosynthetic capacity to reduce costs related to water/fertilizer use/pollinator attraction needs/attraction as well as biodiversity enhancement/carbon sequestration initiatives.

High-density plantings offer greater leaf area index than conventional ones and offer increased canopy coverage, leading to greater solar energy absorption and an increase in photosynthesis, yield, crop yield, shade protection from sunburn and disease outbreak, fruit ripening rates and microbial activity.

Planting density can have an enormous effect on the development of lateral shoots and fruit set, color development and quality traits of fruit. One multi-state trial showed that “Honeycrisp” trees on G.935 rootstock produced larger firmer fruits than did similar varieties grown on conventional or high density plots.

Most fruit species experience much faster lateral shoot growth than terminal growth, an effect compounded by pruning which often triggers compensatory shoot growth to restore a more balanced ratio between their length. Therefore, severe pruning should only be used as a way of controlling tree size if combined with root pruning. Pinch training using spring-type clothespins to direct shoots horizontally has proven an effective method of controlling lateral shoot vigor in fruit trees without diminishing vegetative growth. Pinching also serves to decrease competition between developing leaves and embryonic fruit during critical flowering times and thus helps avoid inflorescence necrosis in varieties predisposed to this disorder.

Diseases

HD orchards’ dense plant populations increase their susceptibility to disease. To minimize this risk, ensure there is enough space between trees so they receive enough light, water, nutrition and air circulation; otherwise they risk succumbing to salt build-up in fruit as well as reduced immune system function.

An active microbial community is critical in mitigating pathogen pressure and maintaining root health in an orchard soil. Orchard soils with higher populations of Trichoderma, Streptomyces and Pseudomonas were more effective at suppressing apple replant disease than those with lower numbers of these microbes.

Apple orchard production can be severely limited by fire blight and Phytophthora rots, two major diseases which impede production. Fire blight outbreaks typically occur during warm, wet spring conditions when young shoots are most susceptible to infection; early bloom inspections and good sanitation practices during planting are effective ways to manage such infection events; however, shorter branches growing from central leaders are more difficult to manage and losses may be greater in newly planted orchards.

Phytophthora rots can lead to fruit loss and extensive rootstock damage, particularly under wet conditions when fruit leaks from infected branches and cankers form at the junction between graft and rootstock suckers. Young orchards especially vulnerable cultivars that rely heavily on susceptible rootstocks may suffer serious infections from this pathogen that may even result in their complete destruction and subsequent replant loss.

Bitter pit is an increasingly serious issue in Virginia, and one key element in its occurrence appears to be rootstock choice. Our 2020 study of Honeycrisp varieties on different rootstocks demonstrated this clearly; of the five examined, B.10 rootstock had the lowest percentage of bitter pit. More work must be conducted over time to assess this rootstock against other possible options for growing Honeycrisp varieties.