Influence of nutrient management and moisture conservation practices on Growth and development of organic baby corn (Zea mays L.) in Assam

Maize (Zea mays L.) is the third most important cereal crop in India as well as in the world next to rice and wheat (Murdia et al., 2016). For diversification and value addition of maize, a recent development is of growing maize for the vegetable purpose, which is commonly known as baby corn. Baby corn is the small (6-7 cm long) and young unfertilized corn ear harvested at the stage of silk emergence (i.e. within 2 - 3 days of silk emergence). It is a profitable crop that allows the diversification of production, aggregation of value and increased income (Pandey et al., 2000). In the present scenario, the use of chemical fertilizers may help in achieving maximum yield of baby corn but they pose serious health hazards and it is a big threat to the sustainability of agriculture. Development of organic production technology for baby corn is necessary for realizing higher yield and economic returns (Galinat, 1985). Assam has tremendous potential to grow crops organically and emerge as the main supplier of organic products in the world’s organic market.
       
In Assam, baby corn is rather a new introduction, so efforts are required to standardize and economize its cultivation. Therefore, the need was felt to standardize organic production technology for baby corn through supplementation of the nutrient requirement through organic manures and biofertilizers. Moisture conservation in agriculture is also very essential in this dynamic climate change. Due to very scanty rainfall during rabi season in Assam, the need for soil moisture conservation was felt. Viable nutrient management is very important for bringing more area under organic crop production.

A field experiment was conducted at Assam Agricultural University, Jorhat during the year 2016-17. The experiment was laid out in factorial RBD with 3 replications. Baby corn variety PAC 321 was used as the test crop. The soil of experimental field was loamy sand, acidic in soil reaction (pH 5.5), medium in organic carbon (0.52%), low in available N (190.24 kg ha^-1), low in available P (20.03kg ha^-1) and medium in available K (160.30kg ha^-1). The experiment consisted of two different factors i.e. nutrient management viz., control, enriched compost 2.5 t ha^-1, vermicompost 2 t ha^-1 incubated with bio-fertilizers, poultry manure 2 t ha^-1 incubated with bio-fertilizers, FYM 2.5 t ha^-1 incubated with bio-fertilizers and FYM 2.5 t ha^-1+lime+ash (1000:10:1) and moisture conservation i.e. no mulch and mulch with paddy straw @ 2 t  ha^-1). The manures were incubated for 15 days with Azotobacter and phosphorous solubilizing bacteria (PSB) @ 0.2% (w/w) each and moisture was maintained at about 25 + (w/w) (Borah et al., 2014). Incubated manures (FYM, poultry manure and vermicompost) and enriched compost were applied at a specified rate as per the treatments mentioned above. The crop was sown on 21^st November 2016 and the first harvest was started on 23^rd February 2017 and completed on 11^th March 2017. Ten randomly selected plants were tagged from the net plot area for recording observations that did not involve destructive sampling. Five plants in the second row in each plot were cut at ground level at each sampling for recording dry matter accumulation. Reading on chlorophyll content was taken by SPAD- 502 chlorophyll meter (a non-destructive sampling method) at 45 DAS and 90 DAS, on the topmost fully expanded leaves. From each plot, 3 readings were taken and the average value was reported. The leaf area index of five randomly selected plants was calculated at 30 days interval up to harvest (Sestak et al., 1971). The leaf area duration of five randomly selected plants was calculated at 30 days interval up to harvest and expressed as days (Power et al., 1967). Cob yield was recorded from the net plot area and expressed in t ha^-1. The NPK contents in different manures are presented in Table 1.
 

In the present study, the growth of baby corn as measured in terms of plant height, number of leaves plant^-1 and dry matter production plant^-1 varied significantly under nutrient management recorded at different stages. The significantly highest value of plant height and number of leaves plant^-1 was recorded in case of enriched compost 2.5 t ha^-1 at all growth stages (Plant height, number of leaves plant^-1 at harvest and dry matter production were furnished in Table 2). This might be due to the fact that enriched compost had highest NPK content as compared to other sources. Similar findings were earlier reported by Kaur and Reddy (2014).
 

                     
Leaf area index is of paramount importance in all crops, because of optimum leaf area required for a maximum light interception, which results in higher photosynthesis (Boote et al., 1996). The values of leaf area index and leaf area duration were highest with the application of enriched compost 2.5 t ha^-1 (LAI, LAD values were presented in Table 3), which can be attributed to the supply of more nitrogen through enriched compost compared to other treatments. With the increased supply of nitrogen, there was a subsequent increase in both LAI and LAD (Kumar and Singh, 2001). Leaf area index decides the efficiency of canopy photosynthesis. The significantly higher leaf area index due to enriched compost application 2.5 t ha^-1 might have resulted in better photosynthesis, thereby contributing to the expression of superior yield attributing characters leading to better yield performance.
 

      
Dry matter production is another important character to express the overall growth and metabolic efficiency of the plant, which ultimately influences the crop yield. The dry matter production is a result of metabolic activities of the crop plant. Application of enriched compost 2.5 t ha^-1 proved significantly superior effects in terms of the total dry matter production of the plant (Table 2). Periodic dry matter production increased with increase in crop age up to maturity. Maximum dry matter production might be due to more plant height, the higher number of leaves plant^-1, increased LAI leading to more photosynthetic rate and accumulation of more assimilates. Similar findings were also reported by Mikhail and Shalaby (1979). The increased dry matter production might be due to better utilization of a nutrient. This corroborates the findings of Thakur et al., (1997) and Luikham et al., (2003).
      
Significantly higher chlorophyll content (expressed as SPAD value) was recorded in treatment enriched compost 2.5 t ha^-1 (Table 3). The chlorophyll content was significantly lowest in control. This clearly indicated the positive influence of nutrient application on chlorophyll formation. Follet et al., (1981) reported that the colouration of chlorophyll depends largely on the amount of nutrients absorbed by the plants from the soils. The significant impact of nutrients as chlorophyll formation has also been reported by Amujoyegbe et al., (2007). Increased chlorophyll content with increasing nutrients, especially nitrogen, has been attributed to the direct involvement of nitrogen as a constituent for chlorophyll synthesis. Leaf chlorophyll concentration is often well correlated with plant metabolic activity (Seeman et al., 1987). Further chlorophyll concentrations have been reported to reflect crop yield also (Blackmer and Schepers, 1995). Thus, higher yields recorded in enriched compost 2.5 t ha^-1 and in FYM 2.5 t ha^-1+lime+ash could also be attributed to the higher chlorophyll contents supported by these treatments.
                     
Growth attributes viz. plant height, the number of green leaves and dry matter production plant^-1 were found to increase significantly with straw mulch treatments as compared to control. This is probably due to the availability of more soil moisture under mulching during the critical cropping period. A similar finding was also reported earlier by Chakraborty et al., (2008).
      
The highest cob yield and corn yield was obtained under treatment enriched compost 2.5 t ha^-1 which might be due to the positive combined effect of yield attributing characters, like number of cobs plant^-1, weight of the cob and length of the cob (Table 4). Improvement of marketable cob yield could be attributed to the higher photosynthetic rates at enriched compost 2.5 t ha^-1 resulting from better light interception, light absorption and radiation use efficiency. This is in consonance with the findings of Madhavi et al., (1995) and Thavaprakash et al., (2005). Since the yield of the crop is a function of several yield components which are dependent on the complementary interaction between the vegetative and reproductive growth of the crop. Increased nutrient availability and uptake with organic N had increased photosynthetic rate and net assimilation rate, which has resulted in more cob yield. Similar observations were reported by Raja (2001) and Kar et al., (2006) who reported an increase in baby corn yield due to nitrogen application.
 

Application of enriched compost 2.5 t ha^-1 in baby corn produced highest growth characters like plant height, number of leaves plant^-1, dry matter production, leaf area index, leaf area duration, chlorophyll content, cob yield with husk (8.165 t ha^-1) followed by FYM 2.5 t ha^-1+ lime+ash (6.495 t ha^-1). Mulching with paddy straw 2 t ha^-1 recorded the higher cob yield (6.172 t ha^-1) over no mulch condition (5.431 t ha^-1).