Effect of Irrigation and Nitrogen on Growth and Yield of Linseed (Linum usitatissimum L.)

An experiment was conducted during rabi season of the year 2013-14 at College Agronomy Farm, B. A. College of Agriculture, Anand Agricultural University, Anand (Gujarat) to study the effect of irrigation and nitrogen on linseed (Linum usitatissimum L.). Higher values of growth characters, yield attributes, seed and straw yield were recorded under irrigation level I3 (0.8 IW:CPE ratio). Each successive increase in the level of N from 30 to 90 kg/ha significantly increased the growth characters, yield attributes, seed and straw yield. The WUE was recorded higher with I1 treatment (0.4 IW:CPE ratio). Application of nitrogen @ 90 kg N ha -1 in conjuction with irrigation at 0.8 IW:CPE ratio produced maximum seed yield (465 kg ha-1).

Linseed (Linum usitatissimum L.) is popularly known as flax, alsi, jawas and ousahalu. It is rabi season annual herb belongs to family Linaceae. Linseed is one of the rabi oilseed crop of India. It is basically an industrial crop cultivated for its seeds and fibres. Its each and every part is endowed with commercial and medicinal importance. Irrigation to this crop is mostly based on physiological growth stages and the latest approach of scheduling irrigation through irrigation water depth: cumulative pan evaporation (IW:CPE) ratio has not yet been amply tried in almost states of India. Therefore, it is important to compare the previous methods with the latest approach of scheduling irrigation to identify the most suitable frequency, time and depth of irrigation for higher yield of linseed. The another major constraint limiting production of crop is poor fertility status of soil and nitrogen is one of the universal deficient plant nutrients in Indian soils. Lack of adoption of improved agronomic package of practices based on agro-climatic condition, is one of the major constraints behind this. Beside application of nitrogen and water, scare and costly resources, must aim at achieving higher benefits from the cultivation of high yielding varieties, especially under limited resource conditions. Since research work on these aspects of linseed is very meager. So that to obtain the necessary information regarding the optimum dose of nitrogen and suitable time of irrigation for linseed, present investigation was under taken to study the effect of irrigation and nitrogen on linseed.

MATERIALS AND METHODS
An experiment was conducted at college agronomy farm, B. A. College of Agriculture, Anand Agricultural University, Anand (Gujarat) during rabi season of the year 2013-14. The soil of experimental field was loamy sand in texture, having low in organic carbon (0.41%) and nitrogen (242 kg ha -1 ) and medium in phosphorus (32 kg ha -1 ) and potash (263 kg ha -1 ) with pH 7.5. The field capacity, wilting point and bulk density of experimental field were 14.59 %, 4.58 % and 1.36 g/cc, respectively with good drainage capacity. The treatments comprising four levels of irrigation (I 1 : 0.4 IW:CPE ratio, I 2 : 0.6 IW:CPE ratio, I 3 : 0.8 IW:CPE ratio and I 4 : Irrigation at critical growth stages (rosette, node elongation, flowering and capsules development stages) and three levels of nitrogen (30, 60 and 90 kg ha -1 ).
The experiment was laid out in split plot design with four replications. Irrigation water of 50 mm (measured with the help of Parshall flume) was allowed to run in each plot at each irrigation.
Calculated quantity of N was applied through urea in two splits. Entire quantity of P with a basal dose of 30 kg P 2 O 5 /ha through single super phosphate was applied at sowing. Linseed was sown on 23 October with seed rate of 10 kg ha -1 .

Effect of irrigation
Treatment I 3 (0.8 IW:CPE ratio) recorded significantly higher plant height (63.13 cm), number of branches per plant (7.33), number of capsules/plant (68.58), test weight (6.68 g), seed yield (412 kg ha -1 ) and straw yield (3524 kg ha -1 ) ( Table 1) and it was remained at par with treatment I 4 (Irrigation at critical growth stages i.e. rosette, node elongation, flowering and capsules The increase in the level of N was responsible for increased number of leaves/plant and leafarea index, causing higher photosynthesis and assimilation rate and metabolic activity and celldivision, which were responsible for the significant increase in the growth characters, yield attributes and ultimately the seed and straw yields. The results of the present investigation confirm the findings of Singh and Verma (1999), Kushwaha (2006) and

Interaction effects (I×N)
Interaction effect between irrigation scheduling and nitrogen levels was found significant with respect to seed yield of linseed (Table 2). Significantly the highest (465 kg ha -1 ) seed yield was noted in treatment combination I 3 N 3 (0.8 IW:CPE ratio + 90 kg N ha -1 ). Whereas, significantly the lowest (357 kg ha -1 ) seed yield was observed in treatment combination I 1 N 1 (0.4 IW: CPE ratio + 30 kg N ha -1 ). The reason might be due to increase in yield attributed to more vigorous crop growth and higher order of yield attributes under frequent irrigation with adequate supply of nitrogen as the atmosphere had high demand of evapo-transpiration and nutrient during crop period and this results in increased seed yield. The findings of this investigation are in closed conformity of results obtained by Reddaih et al. (1993).

CONCLUSION
From the above results, it can be concluded that for securing higher seed yield of linseed, it is advisable to irrigate the crop at 0.8 IW:CPE ratio in conjunction with 90 kg N ha -1 .