Wheeler T A, Leser J F, Keeling J W, Mullinix B
Texas AgriLife Research Texas AgriLife Extension, Lubbock, TX 79403.
J Nematol. 2008 Jun;40(2):147-51.
Terminated small grain cover crops are valuable in light textured soils to reduce wind and rain erosion and for protection of young cotton seedlings. A three-year study was conducted to determine the impact of terminated small grain winter cover crops, which are hosts for Meloidogyne incognita, on cotton yield, root galling and nematode midseason population density. The small plot test consisted of the cover treatment as the main plots (winter fallow, oats, rye and wheat) and rate of aldicarb applied in-furrow at-plant (0, 0.59 and 0.84 kg a.i./ha) as subplots in a split-plot design with eight replications, arranged in a randomized complete block design. Roots of 10 cotton plants per plot were examined at approximately 35 days after planting. Root galling was affected by aldicarb rate (9.1, 3.8 and 3.4 galls/root system for 0, 0.59 and 0.84 kg aldicarb/ha), but not by cover crop. Soil samples were collected in mid-July and assayed for nematodes. The winter fallow plots had a lower density of M. incognita second-stage juveniles (J2) (transformed to Log(10) (J2 + 1)/500 cm(3) soil) than any of the cover crops (0.88, 1.58, 1.67 and 1.75 Log(10)(J2 + 1)/500 cm(3) soil for winter fallow, oats, rye and wheat, respectively). There were also fewer M. incognita eggs at midseason in the winter fallow (3,512, 7,953, 8,262 and 11,392 eggs/500 cm(3) soil for winter fallow, oats, rye and wheat, respectively). Yield (kg lint per ha) was increased by application of aldicarb (1,544, 1,710 and 1,697 for 0, 0.59 and 0.84 kg aldicarb/ha), but not by any cover crop treatments. These results were consistent over three years. The soil temperature at 15 cm depth, from when soils reached 18 degrees C to termination of the grass cover crop, averaged 9,588, 7,274 and 1,639 centigrade hours (with a minimum threshold of 10 degrees C), in 2005, 2006 and 2007, respectively. Under these conditions, potential reproduction of M. incognita on the cover crop did not result in a yield penalty.
在质地较轻的土壤中，翻耕后的小粒谷物覆盖作物对于减少风雨侵蚀以及保护棉花幼苗具有重要价值。开展了一项为期三年的研究，以确定翻耕后的小粒谷物冬季覆盖作物（南方根结线虫的寄主）对棉花产量、根部瘿瘤形成以及线虫季中种群密度的影响。小区试验的主区为覆盖处理（冬闲、燕麦、黑麦和小麦），副区为种植时沟施涕灭威的用量（0、0.59和0.84千克有效成分/公顷），采用裂区设计，重复八次，按随机完全区组设计排列。在种植后约35天，检查每个小区10株棉花植株的根系。涕灭威用量影响根部瘿瘤形成（0、0.59和0.84千克涕灭威/公顷时，每根系的瘿瘤数分别为9.1、3.8和3.4个），但覆盖作物对此没有影响。在7月中旬采集土壤样本并检测线虫。冬闲小区的南方根结线虫二龄幼虫（J2）密度（换算为Log(10) (J2 + 1)/500立方厘米土壤）低于任何覆盖作物小区（冬闲、燕麦、黑麦和小麦小区的该密度分别为0.88、1.58、1.67和1.75 Log(10)(J2 + 1)/500立方厘米土壤）。冬闲小区季中的南方根结线虫卵数也较少（冬闲、燕麦、黑麦和小麦小区每500立方厘米土壤中的卵数分别为3512、7953、8262和11392个）。施用涕灭威可提高产量（0、0.59和0.84千克涕灭威/公顷时，皮棉产量分别为1544、1710和1697千克/公顷），但任何覆盖作物处理均未产生此效果。这些结果在三年中保持一致。2005年、2006年和2007年，从土壤温度达到18摄氏度至禾本科覆盖作物翻耕时，15厘米深度处的土壤温度平均积温分别为9588、7274和1639摄氏度小时（最低阈值为10摄氏度）。在这些条件下，覆盖作物上南方根结线虫的潜在繁殖并未导致产量损失。
