NUTRIENT UPTAKE BY DIRECT SEEDED RICE AND ASSOCIATED WEEDS AS INFLUENCED BY SOWING DATE, VARIETY AND WEED CONTROL

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1 Indian J. Agric. Res.., 47 (4) : , 2013 AGRICULTURAL RESEARCH COMMUNICATION CENTRE / indianjournals.com NUTRIENT UPTAKE BY DIRECT SEEDED RICE AND ASSOCIATED WEEDS AS INFLUENCED BY SOWING DATE, VARIETY AND WEED CONTROL Harjeet Singh Brar and M.S. Bhullar Department of Agronomy, Punjab Agriculture University, Ludhiana , India Received: Accepted: ABSTRACT Nutrient uptake by direct seeded rice and associated weeds was studied in a field experiment during kharif Twenty four treatment combinations viz. six sowing dates (direct seeding on 0 (June 5), 7, 14, 21 and 28 days after nursery sowing (DANS); transplanting 28 DANS); two varieties (short duration PR 115 and medium duration PAU 201) and two weed control treatments (3 hand weedings at 20, 40, 60 days and pendimethalin 0.75 kg ha -1 pre-emergence followed by bispyribacsodium kg ha -1 as post emergence) were evaluated in a split plot design with three replications. Among sowing dates and establishment methods, rice grains in manual transplanting utilized significantly higher amount of nitrogen and phosphorus than all the direct seeding dates 0, 7, 14, 21 and 28 DANS; potassium uptake was at par to direct seeding on 0 DANS. The rice straw utilized the highest amount of potassium in transplanted treatment and was at par to direct seeding 0 DANS; nitrogen and phosphorous uptake did not show any specific trend. The nitrogen and potassium removal by the weeds was the lowest in transplanted check which was at par to direct seeding on 0-7 DANS and for phosphorous removal it was at par to 0-14 DANS. Nitrogen and potassium uptake by rice grain and straw did not vary among varieties, however, phosphorous uptake by grain and straw was significantly higher in case of PR 115 than PAU 201; weeds also removed significantly higher amount of potassium in PR 115 as compared to PAU 201. Among weed control treatments, rice grains in the three hand weeding treatment utilized significantly higher amount of nitrogen as compared to sequential application of herbicides; nitrogen uptake by straw was non-significant. The weeds in herbicidal plot removed significantly higher amount of nitrogen, phosphorous and potassium as compared to three hand weedings. The nutrient uptake by crop was directly related to crop dry matter accumulation and grain yield while nutrient removal by weeds was directly related to the weed dry matter accumulation under different treatments. Key words: Nitrogen, Phosphorous, Potassium, Rice, Variety, Weeds INTRODUCTION Rice (Oryza sativa L.) is the most important cereal crop in Asi a, grown under varyi ng hydrological conditions. It is the principal source of food for more than half of the world population (Nguyen, 2002), especially in South and Southeast Asia, Latin America and Indonesia. In India, it is a dominating staple food crop of fertile and alluvial soils of north west India, particularly Indo-Gangetic plains (Walia and Walia, 2007). It occupies million hectares with a total production of million tonnes of rice (Anonymous, 2011a). In Punjab, rice is a major kharif crop cultivated on an area of about lakh hectares with total production of lakh tonnes of rice (Anonymous, 2011b). Its cultivation is mainly practi sed through transplanting which is cumbersome and labour intensive. This technique requires puddling and continuous ponding of water for first 15 days for establishment of the seedlings. It leads to nutrient losses through leaching besides causing high evapotranspirational losses during hot summer. To meet the water need of transplanted paddy, underground water is being over exploited by excessive pumping resulting into decline in water table. There has been a steady fall in groundwater depth in Punjab (Hira et al., 2004). The fall in depth has accelerated alarmingly in some areas in recent years; e.g., in parts of Ludhiana district in central Punjab, the rate of fall increased from about 0.2 m

2 354 INDIAN JOURNAL OF AGRICULTURAL RESEARCH year -1 during to about 1 m year -1 during (Hamphreys et al., 2010). In 2009, 103 out 138 administrative blocks were over-exploited in Punjab causing serious concern and raising doubt for the future sustainability of the rice-based system. Therefore, of late, need has acutely been felt to develop technically viable and economically feasible alternate technique for growing paddy in this area. In this context direct seeded rice (DSR) provides an option. It saves labour and water and make paddy cultivation cost effective. It matures earlier (7-10 days) than the transplanted crop due to the absence of transplanting shock (Dhyani et al., 2005) and allows timely planting of succeeding wheat crop. It also ensures the timely sowing in a stipulated time frame. Direct seeded rice accounts for 35 per cent of the total rice cultivated area in India (Nageshwari and Subhramaniyan, 2004). It is now fast replacing traditional transplanted rice in areas with good drainage and weed control (Balasubramanian and Hill, 2000). Planting time, location specific variety and weed control methods are three major factors that determines the productivity of a crop. Optimum planting time for a crop is location specific. At a specific location, maximum grain yield can be achieved by planting the crop at the optimum time, which may vary from variety to variety (Reddy and Narayana, 1984). Direct seeded rice crop has a higher nutrient requirement as compared to a transplanted crop because of the higher plant density and greater production of biomass in the vegetative phase (Dingkuhn et al., 1990 and Schnier et al., 1990). Thus, direct seeded rice crops tend to develop nutrient deficiency at the reproductive stage of growth and senesce earlier. Rice varieties exhibit wide variation in the production of high density grains which showed maximum potential for grain filling and test weight (Murty et al., 1992). Rice varieties vary in their seedling vigour, weed competitiveness, submergence and drought tolerance, maturity duration, lodging resistance, affecting the resource utilization and productivity. Low productivity of direct seeded rice is mainly due to heavy crop-weed competition due to early emergence of weeds along with crop seedling due to favorable soil conditions and their rapid growth result in severe competition for nutrients, space, and light. Application of herbicides controlled weeds effectively and made available more nutrients to rice crop and consequently resulted in higher yield (Kumar et al., 2010 and Rana et al., 2000). All these factors affect not only the productivity of crop but also the nutrient uptake by the crop during growth and development. Therefore, a field experiment was conducted to study the influence of sowing time, varieties and weed control methods on nutrient uptake by crop and associated weeds. MATERALS AND METHODS The field experiment was conducted during kharif 2008 at the Student s Research Farm, Department of Agronomy, Punjab Agricultural University, Ludhiana on loamy sand soil, slightly alkaline in reaction, low in organic carbon and available N, medium in available P and K. The field experiment comprised 24 treatment combinations viz. six sowing dates (direct seeding on 0 (June 5), 7, 14, 21 and 28 days after nursery sowing (DANS); transplanting 28 days after nursery sowing), two varieties (PR 115 and PAU 201) and two weed control treatments (3 hand weedings at 20, 40, 60 days and pendimethalin 0.75 kg ha -1 pre-emergence at 2 days after sowing followed by bispyribacsodium kg ha -1 as post emergence at days after sowing) were evaluated in a split plot design with three replications. The rice was seeded directly at 2-3 cm depth in moist seed bed using 50 kg seed ha -1 in rows spaced at 20 cm. In one treatment, nursery was sown on first date of direct sowing and 28 days old seedlings were transplanted manually in the puddled field. Pendimethalin was applied immediately after seeding or transplanting. In direct seeded treatments, it was sprayed by dissolving in 500 litres of water per ha; in transplanted treatment, it was spread uniformly in standing water by mixing in 150 kg sand per ha. Bispyribac-sodium was sprayed 25 days after seeding/transplanting by dissolving in 375 litres of water per ha. All the recommended production technology was followed to grow the crop. A gross plot was kept with 7.5 m x 2.4 m dimensions out of which net plot of 6.5 m x 1.6 m was harvested. RESULTS AND DISCUSSION Weed population and dry matter accumulation Weed population and dry matter increased with delay in direct seeding from 0 to 28 DANS, however, the significant increase was recorded only up to 14 DANS. The transplanting treatment

3 recorded the lower weed density and dry matter and was at par with direct seeding on 0 and 7 DANS (Table 1). Early planted crop accumulated more dry matter and thus exerted more smothering effect on weeds compared to late sown crop. The differences in seeding age helped transplanted crop exert more smothering effect on weeds. Amongst varieties, PAU 201 recorded significantly low weed population and dry matter than PR 115. The droopy lower leaves of PAU 201 curtailed the sunlight and checked weed growth (Pillai, 1977; Thakur et al., 1995; Singh and Singh, 2001). Among weed control, three hand weedings significantly reduced total weed population and dry matter as compared to sequenti al application of pre and post emergence herbicides. Herbicides though gave effective control of many grasses and sedges but poor control of Leptochloa chinensis and few broad leaf weeds increased total dry matter. Repeated hand weedings controlled different flushes of weeds and the weed population and dry matter reduced. Grain and straw yield:the rice seeded directly on the day of nursery raising (June 5) recorded significantly higher grain yield than direct seeding on 21 and 28 DANS. Transplanted crop produced Treatments Vol. 47, No. 4, the highest grain yield that was at par with direct seeding on 0 DANS (Table 1). Higher dry matter accumulation and better weed control in transplanted and early direct seeding treatments increased the grain yield. Among direct sowings, 0, 7 and 14 DANS were at par and were significantly better than 21 and 28 DANS. Direct seeding on 10 June recorded the highest rice grain yield in Punjab (Gill et al., 2006). Low temperature started during last week of September coincide the reproduction phase of late planted crop leading to increased spikelet sterility and poor grain filling. The two rice varieties recorded statistically similar grain yield. Among weed control, three hand weedings produced significantly higher grain yield as compared to sequential application of pendimethalin 0.75 kg ha -1 and bispyribac 0.03 kg ha -1. The crop in the hand weeded plots accumulated more dry matter, due to lower weed pressure and better soil environment, which increased grain yield. The straw yield did not vary due to sowing dates, varieties and weed control. NUTRIENT UPTAKE Nitrogen:The rice grains utilized significantly lower amount of nitrogen in all the direct seeding treatments as compared to transplanted check (Table 2). Direct TABLE 1: Effect of sowing time, variety and weed control on growth and development on weed and rice. Dry matter accumulation at harvest (q ha -1 ) Grain yield (q ha -1 ) Straw yield (q ha -1 ) Data subjected to sq. root transformation. Figures in parenthesis are means of original values. DANS: - days after nursery sowing Total weed count at harvest ( No m -2 ) Total weed dry matter at harvest (q ha -1 ) Date of sowing Direct sowing 0 DANS (June 5) (2.52) Direct sowing7 DANS (June 12) (2.60) Direct sowing 14 DANS (June 19) (6.03) Direct sowing 21 DANS (June 26) (11.72) Direct sowing 28 DANS (July 3) (8.98) Transplanting 28 DANS (July 3) (1.91) CD at 5% NS Variety PR (6.41) PAU (4.84) CD at 5% NS NS NS Weed control Pendimethalin 0.75kg f.b. Bispyribac (7.22) 0.03 kg ha -1 Hand weeding (20, 40 and 60 DAS) (4.03) CD at 5% NS

4 356 INDIAN JOURNAL OF AGRICULTURAL RESEARCH TABLE 2:Effect of sowing time, variety and weed control on nitrogen, phosphorus and potassium uptake by crop and weeds at harvest (kg ha -1 ) in rice. Data subjected to sq. root transformation. Figures in parenthesis are means of original values. DANS: - days after nursery sowing

5 seeding on 0 to 7 DANS utilized similar amount of nitrogen and significantly superior to the later direct seeding dates. The nutrient uptake in the straw did not show any specific trend and was higher in early direct seeding dates as compared to transplanted check. The DSR seems to have retained significantly more nitrogen as compared to transpl ant ed r i ce i n straw; more plant population per unit area might have encouraged DSR for more uptake and retention of nitrogen in straw (Dingkuhn et al., 1990). The nitrogen uptake did not vary among varieties. The rice grains in hand weed treatment utilized significantly more amount of nitrogen than herbicide treated plot; nitrogen uptake in the straw was not influenced. Weeds in the direct seeding on 0 to 7 DANS removed statistically similar amount of nitrogen and were at par to transplanted check which recorded minimum losses due to weeds (Table 2). Higher weed dry matter in late direct sown crop increased nitrogen removal by weeds (Table 1). Transplanted and early direct sown rice brought down the nutrient removal by weeds due to reduced weed i ntensi ty and dry matter accumulation (Table 1). Effective control of weeds by three hand weedings significantly reduced nitrogen removal by weeds as compared to herbicide treatment. Repeated hand weedings in direct seeded rice recorded minimum nitrogen losses due to weeds (Payman and Singh, 2008). Phosphorus: The direct seeded rice grains utilized significantly lower amount of phosphorus than transplanted check (Table 2). Lower weed pressure and higher grain yield (Table 1) increased the phosphorus utilization by rice grains in the transplanted check treatment; the nutrient content did not vary among sowing dates, varieties and weed control (data not shown). The nutrient uptake in the straw did not show any specific trend. Rice variety PR 115 utilized significantly higher amount of phosphorus than PAU 201. Effect of weed control treatments on phosphorous uptake by ri ce grai n and straw was no n- significant. The weeds in the early direct seeding dates, fr om 0-14 D ANS recor ded low er phosphorous losses due to weeds and were at par Vol. 47, No. 4, to transplanted check; the later direct seeding dates, DANS, reported statistically higher phosphorous losses due to weeds owing to higher weed pressure (Table 1). Phosphorous removal by weeds among varieties was not significant while three hoeings significantly reduced the phosphorous losses due to weeds as compared to herbicides. Potassium:The transplanted crop utilized the highest quantity of potassium in grain and straw (Table 2). It was at par to direct sowing on 0 DANS but significantly higher than rest of direct sowing dates. The higher uptake of potassium in transplanted crop could be due to higher nutrient concentration under puddled conditions by the formation of slurry type of structure which restricted water and nutrient losses to the lower depth and provi ded better opportunity for diffusion and uptake of nutrients and proliferation of roots with in the deep puddled layer (Greenland, 1981). The potassium utilization by crop did not vary among v ari eti es and weed co ntr ol treatments. Weed removed si gni ficantly higher potassium when direct sowing was delayed to 21 and 28 DANS (Table 2). Higher potassium uptake by weeds in late direct sowing treatments might be due to higher weed dry matter at harvest (Table 1). Potassium uptake by weeds among varieties was higher in case of PR 115 as compared to PAU 201. Effective weed control by three hand weedings significantly reduced potassium removal by weeds as compared to pendimethalin 0.75 kg ha -1 f.b. bispyribac sodium 0.03 kg ha -1. CONCLUSION The utilization of nitrogen, phosphorous and potassium by rice grains and straw, and nutrient removal by associated weeds in direct seeded rice were similar to transplanted rice when it was seeded directly on the day of nursery sowing. The nutrient utilization by crop and removal by weeds did not vary among short and medium duration rice varieties. The crop in three hand weeding treatment utilized significantly higher amount of nutrients leaving less amounts for associated weeds as compared to chemical treatment.

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