Soil transportation due to harvesting of ginger and turmeric under tillage management practices

Ginger (Zingiber officinale Rosc.) and turmeric (Curcuma longa L.) rhizomes are globally consumed as medicinal spices and their production can be enhanced by tillage practices. However, there is no information worldwide on how harvesting of ginger and turmeric crops from tilled fields can contribute to soil degradation, particularly soil loss due to crop harvest (SLCHcrop). Thus, a 2-year field study was conducted with three tillage practices: zero tillage (ZT), traditional tillage (TT), and minimum tillage (MT) to compare soil transported by ginger and turmeric harvesting under the tillage management system. The harvested rhizomes of ginger and turmeric were separately washed to remove adhering soils (transported soil). Soil transported by ginger (2.45 Mg ha(-1)harvest(-1)) was eight times higher than that by turmeric (0.30 Mg ha(-1)harvest(-1)) regardless of tillage practice due to higher numbers of rhizomatous hairs and rhizome yields associated with ginger. Overall, ginger was higher than turmeric by factors of 9.5 for rhizomatous hair weight and 3.7 for crop yield. SLCHcrop was highest in MT (2.50 Mg ha(-1)harvest(-1)) followed by TT (1.20 Mg ha(-1)harvest(-1)) and least in ZT (0.42 Mg ha(-1)harvest(-1)). Generally, tillage practices increased soil loss by creating a conducive soil environment for the growth and development of rhizomatous hair weight (R-2 = 0.24 - 0.92; P < 0.05) and crop yield (R-2 = 0.86 - 0.95; P < 0.05) which were linearly related to soil transportation. Soil denudation rate (soil degradation) due to ginger (0.025 mm yr(-1)) harvesting was eight times higher than that due to turmeric (0.003 mm yr-1). Rhizomatous hair numbers, rhizome yields and soil management increased soil transportation by ginger and turmeric differently under traditional agriculture. Soil loss by ginger validates the need to conduct further tillage studies under wider textural classes.