The number of individuals of a given species that exist inside a specific sample unit or research area is described as density in plant ecology. The plant population or plant density in a cropped field is the number of plants per unit area.
Optimum plant population
It’s the amount of plants needed to create the most output or biomass per unit area. Any increase beyond this point causes either no change or a decrease in biomass.
Crop geometry is the arranging of plants in different rows and columns in an area to maximise the use of natural resources. The size of the accessible area for individual plants. It is dependent on,
- Patterns of light interception
- Moisture extraction
Plant population, crop output, while yield may be reduced owing to lower plant population below optimal due to difficulty of weak plant stand to intercept maximum available light (Mahajan, 2010).
The impact of planting pattern on light interception, rooting pattern, and moisture extraction pattern on crop yield. Different planting patterns are used to accommodate various weed control and cropping strategies.
Plant geometry is the form of the plant, whereas crop geometry is the shape of the area allocated to individual plants. Changes in inter and intra-row spacing influence crop shape.
It is logical to assume that a square arrangement of plants will be more effective in utilising the available light, water, and nutrients than a rectangle configuration. In wheat, lowering rectangularity by decreasing inter-row spacing below the usual 15-12 cm boosts yield marginally. In square planting, inter culture in both directions is feasible in crops like tobacco, which aids in weed control. However, not all crops benefit from square planting. Groundnut seeded with a 30x10cm (3.33 lakh/ha) spacing yielded more pods than square planting with the same population. By increasing rectangularity or moving toward square planting, pod production is lowered.
The normal approach is to sow the crop with a seed drill. For most crops, wider inter-row spacing and narrower intra-row spacing are fairly prevalent, resulting in rectangularity. This rectangular layout was chosen primarily to make inter-cultivation easier. Inter-row spacing is sometimes maintained, but intra-row spacing is not carefully observed, and seeds are placed in solid rows.
Miscellaneous planting arrangements
Crops are seeded in two directions with seed drills to accommodate more plants and, more importantly, to decrease weed population. Rice, finger millet, and other crops are transplanted at a rate of 2-3 seedlings per hill. Transplanting can be done in rows or at random. Paired row planting is the process of skipping every alternate row and adjusting the population by lowering intra-row spacing. It is usually rehabilitated in order to plant an intercrop.
Plant population and growth
A. Plant development undergoes changes as a result of high plant density. Due to competition for light, plant height increases as the plant population grows.
B. Due to competition for water and nutrients but not for light, a slight increase in plant population may not raise but reduce plant height.
C. Population pressure affects leaf orientation as well. Under high plant densities, the leaves are upright and slender, with larger vertical intervals. This is an attractive design.
Plant population and yield
The reduction in the number of earls or panicles causes a decrease in each plant yield at high plant density. For example, at 3.33 lakh plants/ha (30x10cm), Redgram produces roughly 20 pods per plant, but at 50,000 plants/ha, it yields more than 100 pods each plant (80x25cm).
Plants become barren at very high population levels, hence the optimal plant population is required for maximum output.
Importance of crop geometry
1. Any crop’s yield is determined by the ultimate plant population.
2. Plant population is determined by germination percentage and field survival rate.
3. In rainfed situations, a large plant population depletes soil moisture before maturity, whereas a low plant population leaves soil moisture unused.
4. When soil moisture and nutrients are abundant, a large plant population is required to effectively use additional growth elements such as solar radiation.
5. Because of the wide spacing, each plant output will be higher when the plant population is low.
6. Individual plant production will be poor in high plant populations due to limited spacing and plant competition.
Factors affecting plant population
A. Genetic factors
1. Size of the plant
2. Elasticity of the plant
3. Foraging area or soil cover
4. Dry matter portioning
5. Crop and variety
B. Environmental factors
1. Time of sowing
3. Fertilizer application
4. Seed rate
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