Estimation of border effect on yield of rice and nutrient uptake

The experiment was conducted at Agronomy Research Field of Bangladesh Agricultural Institute, Gazipur during 2019 to quantify the border effect on rice. The experiment was set in a randomized complete block design with twelve replications. The treatment was non border (T1) and border (T2). Border treatment (T2) had signifi cant and positive infl uence on different parameters of rice. Grain yield and associated yield components improved in border treatment. Border effect was estimated at 8% in respect of grain yield. Increased tillers/hill (18%), fi lled grains/panicle (47%), grain weight/panicle (45%), grain growth (12%) weight of 1000-grain (0.97%), biological yield (4%) and harvest index (4.5%) were observed in border rows. Rice plant both fl owered and matured 3 days earlier in border rows. Carbon input and uptake of N, P, K, S and Zn by rice were found higher values in border treatment. Carbon accumulation increased about 4.4% in border rice. Two lines/rows of rice hill should be excluded for harvesting of plot yield. Otherwise 8% yield will be deducted in actual yield calculation for eliminating the border area effect/border effect (for 2 lines/rows of hills around the plot). Research Article Estimation of border effect on yield of rice and nutrient uptake MAK Mian* Principal Scientifi c Offi cer, Agronomy Division, Bangladesh Agricultural Research Institute, Gazipur 1701, Bangladesh Received: 29 July, 2021 Accepted: 24 August, 2021 Published: 25 August, 2021 *Corresponding author: MAK Mian, Principal Scientifi c Offi cer, Agronomy Division, Bangladesh Agricultural Research Institute, Gazipur 1701, Bangladesh, E-mail:


Introduction
Border is the outer margin or side of a plot or crop fi eld.
Outer margin of crop fi eld is exposed more as compared to inner side or centre of the plot. Plants in the outermost row next to the unplanted alley showed a general increase in yield and growth as compared to the center row [1]. This phenomenon has been referred to as 'border effect'. Main causes of border effect are considered to be advantageous environmental factors on above the ground, such as higher solar energy, air circulation etc. Consequently, crop plants of border row get more light and more opportunity for gaseous exchange like carbon di oxide intake and release of oxygen [1].
Transpiration of crop plant is also infl uenced by border. Crop plants of border get more aeration as compared to inner side or centre of the plot. Consequently, the rate of transpiration decreases in a canopy due to density of foliage, shading effect and decrease of air movement inside of the rows [2,3]. More light interception enhanced total photosynthesis of crop plants of border. Leaf Area Index (LAI) in border rice increases as compared to centre due to more tillering. More tillering occurs due to advantageous environment of the outermost row [1].
As Leaf Area Index (LAI) increases so does light interception, causing increases in photosynthesis up to a critical LAI value [4]. Thus, a greater number of tillers of outer rows increased LAI resulting higher photosynthesis. More photosynthesis results in more dry matter production in the plant system ultimately contributes to higher yield of crop [5]. The greater rate of Net Assimilation Rate (NAR), Relative Growth Rate (RGR) and carbohydrate accumulation during grain ripening stage resulted in higher grain yield of rice in border [1].
They also mentioned that nutritional supply from alley and wider unplanted distance also increased yield in border rice.
Hereby physiological process of yield formation of crop plant is infl uenced by border effect. There are scientifi c evidences of border effect on crop yield. A signifi cant difference in yield (21.9 to 69.6%) and yield components was observed between outermost rows and inner rows of experimental plots, 2017) [6]. Rice plants grown in outmost fi rst and second rows in paddy fi eld produced averaged 30% more grain yield than that in center rows [7]. The fi rst and the second row next to the unplanted alley consistently gave signifi cantly higher grain yields than the centre rows but no evidence was found that border effect reach beyond the second outermost row. If the increase was very large, yield of the second outermost row were signifi cantly decreased as compared to fi rst row [8]. method by Nelson and Sommers 1982 [16], Nitrogen through semi micro-Kjeldhal method by Bremner and mulvaney 1982 [17], P through Molybdate ascorbic acid method by Olsen and Sommers 1982 [18], K directly through fl ame photometer from digest, S by turbidmetric method by Tabatabi 1982, Zn through Atomic absorption spectrophotometer and Calcium chloride extraction method). Each nutrient was measured by 5 repeated number of each replication. Nutrient uptake was also computed on the basis of nutrient concentration (both grain and straw).
Collected data was subjected to statistical analysis. Hence, no need of LSD value because of only two treatments since F test signifi cance about parameters, off course indicated the variation (only higher and lower) in two treatments.

Crop character
Plant height, tillers/hill, length of panicle, total grains/ panicle, fi lled grains/panicle and unfi lled grains/panicle of rice signifi cantly varied between non border and border treatment (Table 1). Plant height increased in non border (122 cm) rows as compared to border rows (117 cm). Plant height increased in non border rows due to inter tiller competition for receiving light. Tall plant is advantageous in light competition [19], this is why the increased plant height in the dense treatments is depicted by Gruntman, et al. [20]. Shading effect in central rows enhanced to produce taller plant due to variation of hormonal activities. Number of tillers/hill increased (18%) in border row due to getting more space (Table 1). Advantageous environment, more available nutrient near alley helped to produce more number of tillers/hill in the outermost row [1].
Plants in border rows produced higher number of tillers from those in the centre of plots was also found by Wang, et al. [9]. Weight of 1000-grain (26.03 g), grain growth (0.96 g/grain/ day) and grain weight per panicle (4.47 g) were observed higher in border rows ( Table 2). Better dry matter partitioning into grain and grain fi lling possibly enhanced 1000-grain weight. Similarly, 1000-kernel weight increased in border row of corn [11]. Grain yield (6.61 t/ha), straw yield (8.89 t/ha) and biological yield (14.50 t/ha) gave higher values in border rows of rice (Table 2). Better crop growth helped in production of higher dry matter as well as higher biological yield which ultimately contributed to higher grain yield in border rows ( Table 2). The results are in agreement with the report of Wang, et al. [19].
Higher harvest index (46) was calculated in border rows that was possibly happened due to higher dry matter partitioning in grain as compared to non border rows. Dry weight of grain signifi cant border effect on grain yield was observed in the outmost row, but not in the second and third outmost rows in comparison with the center rows. Higher biomass production, more panicles per m 2 and spikelets per panicle, and higher grain-fi lling percentage were responsible for the border effect [9]. The two external rows yielded up to 40% more than the two innermost in wheat [10]. Analysis of yield components in border rows indicated that the number of kernels per ear, 1000-kernel weight and yield per plant of corn increased in border row and stopped decreasing after the second row of the border [11]. No more than three border rows of all the cultivars had marginal superiority (border effect) under high density, but about 90% of all the cultivars had border effect no more than two border row in maize [12]. Higher number of cobs per plant in border rows of maize was also observed by Mian [5]. Border row effect was estimated at 16% in soybean in single row soybean (4.88 m long and 11.80 cm between rows) [13]. Yield of cucurbit (cv. 'M 21') was reduced 13% in central rows from that of bordered row [14]. Rice plants grown in border rows had higher number of panicles per hill and a higher number of spikelet per panicle [7].
Plants in border rows performed differently producing higher tillering from those in the centre of plots tending to depress the performance of adjacent plants [9]. Nutrient uptake also varied in borders as compared to center rows [1]. Outer rows got more nutrients facility due to unplanted alley of the border.
But research on border effect of crop as well rice in Bangladesh is scanty. Therefore, the study was undertaken to quantify the border effect on rice. (5.81 t/ha) and straw (6.98 t/ha) were also found higher in border rows due to corresponding higher weight of grain and straw before oven dry (Table 3). Better growth at border rice plant increased dry matter of grain and straw. Flowering of rice plant occurred three days earlier in border rows possibly due to advantageous micro environment. Border rows of rice plant got advantageous environmental factors like higher solar energy and air circulation as stated by Sato and Takahashi [1]. The results also have been supported by the fi ndings of Rezazadeh, et al. [21]. They found earlier fl owering (7.5 days and 46.6 days earlier) in full sunlight as compared to shading (45% and 65% shading respectively) in fi respike (Odontonema strictum). Central rows of rice got mutual shading as compared border rows. Hence, earlier fl owering occurred in border rows as infl uenced by more light availability than in central rows. Moreover, better growth of rice plant might have enhanced early fl owering. Three to four days early fl owering of Bt. brinjal (eggplant) in higher plant growth has been reported [22,23]. As the earlier fl owering resulted in earlier maturity (3 days earlier) of rice in the border whereas grain fi lling duration (30 days) was static both in border and non border (Table 3). Better growth also enhanced earlier fl owering of rice plant has been described by Mian [5]. However, the results fi nally reveal that grain yield increased 8% due to border effect having some advantageous infl uences.

Carbon input and uptake of other nutrient
Carbon input and uptake of N, P, K, S and Zn by rice grain showed higher values in border treatment as compared to non-border treatment (Table 4). Higher dry matter rendered higher C input and other nutrients uptake in plant system [5,24]. Higher C input observed in border rows possibly happed due to higher photosynthesis in more light availability and interception of it in border rows as compared to central rows where mutual shading occurred [21]. Higher dry matter production resulted in higher C input indicating more carbon accumulation through photosynthesis from the atmospheric carbon di oxide (CO2) in the plant system in the border rows.

Conclusion
Yield components and grain yield of rice improved in border rows. Border effect was estimated at 8% in grain of border rice.
Two lines/rows of rice hills should be excluded for harvesting of plot yield. Otherwise 8% yield will be deducted in actual yield calculation for eliminating the border area effect/border effect (for 2 lines/rows of hills around the plot).   Table 6: Total C input and uptake of total N, P, K, S and Zn by rice (grain +straw) under non border and border treatment (2019).