Effect of Organic and Inorganic Fertilization on Growth and Yield of French Bean (Phaseolus vulgaris L.) in Fiji 

French bean is used both as dry seeds or as green pod vegetable and it is in increasing demand in throughout Fiji. But limited agronomical information is available for its cultivation which is one of the barriers in increasing its production in country. Due to poor nodulation, it is very inefficient in biological nitrogen fixation. It requires higher dose of nitrogen fertilizer for enhanced productivity (Ram Gopal et al., 2005). Use of chemical fertilizer alone increases the crop yield in the initial years but adversely affect the sustainability subsequently. The cost of chemical fertilizers is also increasing day by day. Therefore, to low dependence on chemical fertilizers along with sustainable productivity are vital issues in modern agriculture which can be realized possibly by integrated plant nutrient supply sources like farm yard manure (FYM) and Poultry manure (PM) which are cheap and easily available in local condition. Application of both chemical and organic fertilizers is needed for the improvement of soil physical properties and supply of essential plant nutrients for higher yield (Purakayaotha and Bhatnagar 1997).
 
Band et al., (2007) reported that related to human population explosion, the demand for the crop has increased significantly, leading to the extensive use of chemical fertilizers without any consideration for soil health and quality, which is a critical factor for realizing sustainable yield. The chemical fertilizers application not only increases production cost but gradually decreases the partial productivity and causes high risk to the sustenance of the basic system. The minimum application of organic manures has also caused soils deficient in macro and micronutrients.
 
The balance of organic and inorganic fertilizer use is the key to manage the soil nutrients properly (Triwulaningrum, 2009). This is due to the organic fertilizer and inorganic fertilizer contributed many advantages of each. Application of inorganic fertilizer is a faster way to maintain the productivity of crop because the nutrients are releasing nutrients (e.g. NPK nutrients) form which is easily available to plants. While the organic matter may consist of manure organic (cow manure, green manure) able to improve the physical, chemical and biological soil. The use of organic and inorganic fertilizer able to increase yield of green bean (Duaja, 2015) and also using cultivars, plant spacing, dosages of organic and inorganic fertilizers and irrigation (Sherawat and Singh, 2009; Datt et al., 2013; Ghosh et al., 2014).
 
The present study was planned to study the effect of organic and inorganic fertilizers on growth and green pod yield of French bean.

 
Harvest index (%) = Grain yield/ Biological yield × 100

 
 

Growth
 
Improvement in growth characters is considered to be pre-requisite to increase yield of any crop. Combinations of NPK fertilizers with organic manures had significant positive effect on growth characters as compared to sole application of inorganic fertilizers (Table 1).
 

 
Application of T1:100% NPK+ PM @ 5 t ha^-1 recorded maximum plant height (37.47 cm), number of branches (6.47 plant^-1), number of leaves (23.33 plant^-1) and leaf area (108.47 dm²) followed by T2: 100% NPK + FYM @ 12 t ha^-1 and T3: 50 % NPK + PM @ 5 t ha-1.T6: FYM @ 25 t ha^-1 recorded the minimum plant height (31.23 cm), number of leaves (17.60 plant^-1)  and leaf area (77.60 dm2)  among all the treatments whereas T5: PM @ 5 t ha^-1 recorded the minimum number of branches (4.13 plant^-1).
 
This emphasizes importance of organic manures addition combined with inorganic fertilizer which increases the availability of nutrients substantially resulting in positive effect on growth parameters. Poultry manure which was readily available to the plant higher C: N ratio, profuse supply of available nutrients to the soil with comparatively lesser retention in roots and more translocation to the aerial parts for protoplasmic proteins and synthesis of other compounds. The added organic manures in term of PM would have improved the soil physical condition and better nutrient availability which resulted better plant growth. The increased growth characters might be due to higher accessibility of nitrogen which improved the plant growth as nitrogen after absorption by the plant is transformed in to amino acids, building blocks of protein which might have escalated rate of meristematic activity resulting in better growth characters. These results are in conformity with the results of Sathe et al., (2007), Choudhari et al., (2001), Band et al., (2007) in French bean.
 
Production potential of French bean
 
The results revealed beneficial effect of combining poultry and farm yard manures with NPK fertilization over sole application of NPK fertilization (Table 2). All the treatments recorded significantly higher pod length, diameter of pod, number of plant^-1 and pod weight plant^-1 than sole application of NPK except T6 which also recorded lowest values. Application of T1 recorded maximum values of all yield attributing characters such as pod length (12.76 cm), pod diameter (0.93 cm), number of pods plant^-1 (41.51) and pod weight (56.08 g plant^-1) and T6: FYM @ 25 t ha^-1 recorded the minimum (9.8 cm, 0.59 cm, 27.44 plant^-1 and 31.24 g, respectively) values of these characters among all the treatments. It seems that balanced nutritional environment improved yield characters.
 
T1 was found significantly superior to other treatments and recorded maximum yield (30.38 q ha^-1) followed by T2 (25.82 q ha^-1) and T3 (24.18 q ha^-1) (Table 3). T2 and T3 recorded at par yield with each other however these, were significantly superior to all other treatments. While T6 recorded minimum yield (16.27 q ha^-1).
 
 
T1 was found significantly superior to other treatments and recorded maximum stover yield (39.55 q ha^-1) followed by T2 (34.91 q ha^-1) and T3 (34.60 q ha^-1) (Table 3). T2 and T3 recorded at par stover yield with each other however, both recorded superior stover yield than all other treatments. While T6 recorded minimum yield (26.73 q ha^-1). Similar trends were recorded in biological yield of the French bean crop in the trial.
 
Harvest index varied significantly due to different fertilization combinations during crop period.  T1 was found to be significantly superior followed by T2 and T3. Highest and lowest harvest index was recorded in T1 (43.44) and treatment T7 (37.75), respectively (Table 3). All the treatments varied significantly with respect to other treatments.
 
Production efficiency (Kg day^-1 ha^-1)
 
The maximum production efficiency (60.77 Kg day^-1 ha^-1) was recorded in T1 which was significantly higher compared to all other treatments. Minimum production efficiency (38.73 Kg day^-1 ha^-1) was recorded in treatment T6 (Table 2). This might be because of increase in grain yield under T1 which also enhanced production efficiency per day.
 
The efficiency of inorganic fertilizers is much pronounced when they are combined with organic manure. Higher vegetative growth might have helped in synthesis of greater amount of food material which was later translocated into developing pods resulting in increasing pod length and pod diameter.
 
Treatment T1 recorded significantly superior (30.38 q ha^-1) pod yield than inorganic fertilizers or organic manure alone for growth and yield of French bean. This was followed by T2, T3, T4, T5 and T7.
 
This might be due to corresponding response to increased yield attributing characters attained previously under this treatment. This finding has close conformity with Choudhari et al., (2001), Sathe et al., (2007) and Kumar et al., (2009) who reported the highest green pod yield ha^-1 in French bean was due to combine application of organic and inorganic fertilizers.

We sincerely acknowledge College of Agriculture, Fisheries and Forestry, Fiji National University, Fiji for providing field staff, facilities and assistance in conducting this research.