Response of Red Hot Pepper (Capsicum annum L.) to Water and Nitrogen under Drip and Check Basin Method of Irrigation

MATERIALS AND METHODS

The experiment was conducted at Research Farm of Punjab Agricultural University Department of Soil and Water Engineering, Ludhiana (30°56’N, 75°52’E and 247 m.s.l.) in India during the summer 2004 and 2005 (first week of march to first fortnight of October). Geologically the farm area forms a part of the trans Indo-Gangetic alluvial plains. The soil of the experimental field was loamy sand in texture. The soil was low in available nitrogen, medium in available phosphorus and rich in available potassium (Table 1).

The soils have no salinity and drainage problem and water table is more than 20 m deep. The treatment comprised two levels of water supply through drip and one through check basin method of irrigation. In check basin (surface flooded) method the irrigations were provided on the basis of 1.0 cumulative pan evaporation (1.0xEpan). For each check basin method of irrigation water was applied when cumulative Epan become 7.5 and irrigation water measurements were made by Parshall Flume. However, in drip irrigation water was applied every second day of irrigation equivalent to cumulative Epan or 50% of it depending upon the treatment. In check basin method total 12 irrigations were applied throughout the season. The N was tried at the rate of 100, 75 and 50% of recommended dose of 75 kg ha^-1 at all the three irrigation treatments. All these treatments combinations were sown in paired row planting. The paired row planting method was used to reduce the cost of drip irrigation system as there was one lateral for two rows of each pair instead of two laterals. In paired sowing, the row to row space between paired rows was 30 cm and row space between pairs was 60 cm and plant to plant spacing in a row is 30 cm.

Table 1:	Physical and chemical properties of soil

The schematic representation of the layout of the experiment and drip in the experimental plot is detailed in Fig. 1. The experiment was conducted in split plot design having two levels of water supply through drip and one through check basin method of irrigation in main plot while nitrogen treatments placed in sub plot having three replications. The cultivar CH-1 of hybrid chilli was used for experimental study in both the seasons. In check basin method of irrigation half the N was applied after first irrigation and second half after first picking. Whole of phosphorus was basal applied (before sowing) in all the treatments. For the establishment of crop after transplanting, the crop was irrigated at regular interval for 1st 15 days irrespective of irrigation treatments and thereafter it was irrigated on the basis of Epan ratio. The drip system consisted of polyethylene lateral of 12 mm in diameter, laid along each row. The laterals have in line dripper at 30 cm distance. The drippers had a discharge rate of 3 L h^-1 under an operation pressure of 1 kg cm^-2. The different levels of water supply were maintained by managing the number of holes in each lateral. In drip irrigation system, N was supplied at 20 day interval in eight equal doses starting from 15 days after transplanting. All other recommended package of practices relating to weed and plant protection measures were followed. Different plant growth characteristics, yield attribute and yield were recorded for all the treatments. For computation of water use efficiency, red pepper yields per hectare were divided by irrigation water applied and expressed as q (ha cm)^-1. Similarly for agronomic efficiency of nitrogen, red pepper yield were divided by the amount of N in kg ha^-1 applied in different treatments. This AEN has been reported as q (yield) kg^-1 N. For root length measurement, plants were harvested with most care. The sides of plants, 60 cm from each side were dug 1m deep and the plant along with the soil was lifted. Later the roots were washed with a fine jet of water by keeping it over a set of sieves of varying pore size. The soil particles were separated from the roots. Root length was estimated by modifying the method of Habib (1988). In order to measure the root length, the following procedure was adopted. The roots of capsicum were divided into categories: L₁ (1-2 cm diameter), L₂ (1-2 mm diameter), L₃ (1-0.05 mm diameter), L₄ (<0.05 mm diameter). The lengths of 50 randomly selected roots were measured using a scale in each category (A).

Fig. 1a:	Layout of experimental site

Fig. 1b:	Layout of the drip system in the experimental plot

This material was subsequently dried and weighed (X). The rest of the roots in this category were also dried and weighed for the total weight of roots (Y). Total root weight was M.

A factor (F) was derived by dividing the length of 50 roots by its dry weight

This factor was multiplied with total dry weight of the root (M). The result gave the length of root in this category

The same procedure was repeated for the roots in different categories. Finally the length obtained for different categories were added up to get the total length of the roots

Results were statistically analysed using standard procedure for split plot design. Means were compared using Least Significant Differences (LSD) at the 5% probability level as per Gomez and Gomez (1984).

RESULTS AND DISCUSSION

Vegetative growth and yield parameters: The plant height and branches/plant responded significantly with different levels of drip and check basin method of irrigation. The highest plant height (62.5 cm) was recorded with drip irrigation at 1.0xEpan, while the lowest at (52.8 cm) with check basin method of irrigation at 1.0 xEpan (Table 2). More branches/plant were recorded with drip irrigation than check basin method of irrigation. There was a significant increase in size (length) and weight of fruits in the plots irrigated through drippers compared to surface irrigated plots. The maximum fruit weight was observed under drip irrigation at 0.5xEpan followed by drip irrigation at 1.0xEpan. Irrespective of irrigation treatments, with 50% decrease in rate of N application than recommended dose, there was an significantly fall in plant height, branches/plant and fruit size. Highest red pepper yields were recorded from the plants irrigated through drip irrigation compared to check basin method of irrigation. The highest yield (274.09 q ha^-1) was recorded with drip irrigation at 0.5xEpan, however statistically same with drip irrigation at 1.0xEpan, but significantly higher than check basin method of irrigation. The drip irrigation at 0.5xEpan resulted increase in red pepper yield to the tune of 37.3% over check basin method of irrigation. The graded doses of nitrogen did not influence the red pepper yield significantly. The highest yields with drip irrigation may be attributed mainly owing to good vegetative growth in terms of higher plant height, more branches, fruit size and higher fruit weight than check basin method of irrigation (Table 2). This may be because of frequent and consistent application of water in the vicinity of roots, which provides a good soil moisture regime in the crop root zone throughout the life period of crop. As the plant height and number of branches increased, new nodes for flower and fruit development appeared resulting in an increase in total yield. These results are in conformity with Antony and Singandhupe (2004). Manunatha et al. (2001), Shirgure et al. (2001), Cetin and Bilgel (2002) and Tiwari et al. (2003) who also reported beneficial effect of drip irrigation on growth and yield of different vegetables. The check basin method of irrigation not only resulted in wastage of water in deep percolation below root zone, but also sets a chain of undesirable reaction such as leaching of available plant nutrients and consequently development of soil problem and poor aeration resulting in reduced crop yield. These results are in conformity with Gutal et al. (1990), who observed higher red pepper yield under drip irrigation as compared to surface irrigation.

The interaction effect of irrigation treatments and varied nitrogen doses on red pepper yield was also found significant. The perusal of data in Table 3 revealed that when recommended level of nitrogen was applied through drip irrigation at 1.0xEpan, a significantly higher red pepper 255.0 q ha^-1 was obtained as compared to 216.1 q ha^-1 in check basin method of irrigation. It further revealed that when half quantity of recommended nitrogen was applied through drip irrigation at 0.5xEpan, the red pepper yield increased by 40.2% over check basin method of irrigation. The data further elucidated that under check basin method of irrigation, the decrease in N dose from the recommended level resulted an significant reduction in pepper yield, while in drip irrigated crop, the red pepper yield was found statistically same at all the level of nitrogen which revealed that there is substantial saving of nitrogen when the crop was drip irrigated as compared to check basin method of irrigation.

Water and nitrogen use efficiency: The total water expenses and Agronomic Efficiency of Nitrogen (AEN) at various levels of water supply is reported in Table 2. The maximum amount of irrigation water was applied in case of surface irrigation at 1.0xEpan (940 mm) while the minimum was with drip irrigation at 0.5xEpan (389 mm).

Table 2:	Effect of treatments on different parameters of hot red pepper (Mean of 2 years)
DI: Drip irrigation, q = Quintal, NS = Non Significant

Table 3:	Interaction effect of irrigation treatments and varied levels of nitrogen on red pepper yield in q ha-1 (Mean of two years)

The WUE increased from 0.212 to 0.385 q ha^-1 mm in drip irrigation as compared to check basin method of irrigation when it was applied at 1.0 Epan. Drip irrigation at 0.5xEpan registered much higher water use efficiency as compared to 1.0xEpan when the water was applied either through drip or check basin method of irrigation. The highest water use efficiency obtained with drip irrigation at 0.5xEpan was owing to more yields of red pepper along with considerable saving of irrigation water compared to check basin method of irrigation. The results corroborated with those of Manjunatha et al. (2001), Cetin and Bilgel (2002) and Tiwari et al. (2003). The AEN at drip irrigation of 0.5xEpan and 1.0xEpan remained statistically same, however increased significantly over check basin method of irrigation. Further irrespective of irrigation treatments, the nitrogen use efficiency increased with the decrease in application of nitrogen. Lesser NUE at higher level of nitrogen dose indicated that excessive N application may shift the balance between vegetative and reproductive growth toward excessive vegetative development, thus delaying crop maturity and reducing red pepper yield.

Root characteristics: The data on root length (Table 2) revealed that, varied level of nitrogen did not influence the root length significantly, but significantly influenced by irrigation treatments. A cursory examination of data revealed that root length increased gradually at lower levels of irrigation in drip treatment. The root length in check basin method of irrigation was found minimum (18.4 m). Drip irrigated plants received water once in two days, whereas water applied at larger intervals in surface irrigated crops. Osmotic adjustment and prolonging root cell expansion (Sharp et al., 1990) had been described as a cause for increased root length in mildly stressed plants than well watered plants (Jupp and Newman, 1987), so at lower level of drip irrigation, root length was maximum (36.3 m), because, though the crop received water once in two days, the amount of water applied was less. In surface irrigation, due to larger interval between irrigation, this treatment suffered maximum water stress as compared to other treatments. This severe water stress has stopped the root elongation, as evident from less root length in the data.