Nutrient Release during Residue Decomposition of Weeds Mown at Different Times in a Persimmon Orchard

Abstract

Decomposition and nutrient release of the residue subsequent to mowing weeds remain poorly understood in persimmon orchards of South Korea. The litterbags including various weed residues were deposited on the soil surface under the tree canopy to simulate the fate of weeds mowed on 13 May, 13 July, and 13 September 2011 and 2012. Rate of decomposition and nutrient release of the residues depended on different mowing times. Residual dry mass (DM) of the 13 May weeds decreased by 17% -21% of initial DM during 1 month and by 63% -71% until 2 months after litterbag deposition, and they released 51% -67% of nitrogen (N), 54% -55% of phosphorus (P), and 92% -94% of potassium (K) of respective initial amount until the first 2 months. The 13 July weeds rapidly decomposed during the first month, accounting for 51% -64% of DM and released 49% -67% of N, 27% -54% of P, and 76% -77% of K. When mowed on 13 September, the weed residue decomposed slower and longer than the 13 May and 13 July weeds, losing 48% -51% of DM, 36% -39% of N, 60% -64% of P, and 70% -77% of K during the first 2 months but continuing an active decomposition even at 6 months after the deposition. The results indicated that time of supplemental fertilization should be adjusted depending on mowing times, and the mowing times be controlled to meet seasonal demand of persimmon trees for nutrients.

Residue Decomposition and Nutrient Release of Two Weed Species Mown at a Persimmon Orchard in Mid-May

“…Due to similar environment, nutrient releases in this study were consistent with results of our previous study that residue, mixed with several weed species, released mostly N, P, and K for 2 months after litterbag deposition (Choi et al, 2017). As previously reported for organic substrates (Jalali and Ranjbar, 2009;Ranjbar and Jalali, 2012), N release followed the residue decomposition more closely than P and K releases.…”

“…A similar pattern of nutrient release from green manures has been observed in the previous studies (Ferreira et al, 2014;Choi et al, 2017), although the plant species were different, indicating that the mineralization process depends on the decomposition rate (Talgre et al, 2012). Changes in nutrient release from weed residues in this study differed slightly from those of other cover plant residues (Seo et al, 1998;Lupwayi et al, 2006;Jahanzad et al, 2016).…”

“…Unlike cover crop residues, very little information is available on nutrient release from weed residues under the orchard conditions. In our previous study in the persimmon orchard (Choi et al, 2017), green manure residue mixed with various weeds in spring decreased by 63 -71% after 2 months of litterbag deposition on the soil surface, and the residue released 51 -67% of N, 54 -55% of P, and 92 -94% of K during the time. However, the release of mineral nutrients from green manures of dominant spring weeds in the orchard has not been evaluated.…”

“…K release has also been known to depend less on microbiological decomposition of the residues, compared with N or P (Marschner, 1995;Lupwayi et al, 2006;Talgre, 2012). Therefore, K release could continue from residues of weeds mown in autumn even during winter when decomposition could not be active (Choi et al, 2017).…”

“…transiens had begun to grow ears and V. hirsuta was flowering. To simulate the fate of the two weeds on the soil after mowing, the litterbag deposition was designed as described in previous studies (Seo et al, 1998;Talgre et al, 2014;Jahanzad et al, 2016;Choi et al, 2017). The litterbags were made of 60-mesh nylon fabric with dimensions of 50 × 25 cm.…”