Evaluating direct dry-seeding and seed-priming used with the system of rice intensification vs. conventional rice cultivation in Pakistan

Establishing rice (Oryza sativa L.) crops by direct-seeding requires less water and less labor than transplanting. However, farmers need to know the net effects of suites of practices. So, evaluations of direct-seeding should also consider its interactions with other factors, including a practice, such as seed-priming. This paper reports on an experiment conducted in 2014 and 2015 at University of Agriculture, Faisalabad, Pakistan. Three interacting factors were assessed: crop establishment by direct dry-seeding vs. transplanting of seedlings; crop management with either the System of Rice Intensification (SRI) or conventional methods, which include continuous flooding rather than alternate wetting and drying; and seed-priming, comparing no priming with both hydropriming with water and osmopriming with CaCl₂. Leaf area index, leaf area duration, crop growth rate, and net assimilation rate were significantly affected by all three factors evaluated. Best performance resulted from transplanted seedlings grown from osmoprimed seeds and raised with SRI management. Overall, direct-seeding did not perform as well as transplanting, the major finding. Lower yield with direct-seeded rice (DSR) was attributable to plants having fewer productive tillers and grains after early rapid growth. Osmopriming with CaCl₂ produced highest grain yield in the trials, 3.96 t ha⁻¹ vs. 3.39 t ha⁻¹ with no priming; highest straw yield of 13.8 t ha⁻¹ vs. 13.3 t ha⁻¹ with no priming; and Harvest Index of 28.7% vs. 25.6% with no priming. Hydropriming produced intermediate values. Osmopriming significantly improved phenological and grain-quality attributes. Transplanting osmoprimed seedlings under SRI management gave the highest economic benefit ($642 ha⁻¹).