The effect of irrigation and weed control by various mechanical and chemical means was evaluated over a 4-yr period on newly planted pecans [Carya illinoensis(Wang.) K. Koch]. Weed control effect on tree growth became evident in the second growing season, and became more pronounced after the third and fourth season. After the fourth season, the maximum increase in tree diameter (384%) was achieved with comprehensive, herbicide-based weed control. Mowing provided a 224% increase, which was equivalent to the untreated (229%). Disking and selective chemical control of grass weeds resulted in 339 and 292% increase, respectively. Cumulative increase in tree diameter was 316 and 271% with and without irrigation, respectively.

Pecan (Carya illinoinensis) leaf elemental concentrations are the industry standard to guide fertility programs. To provide meaningful information, a standard index tissue collected at a specific development stage is required along with established elemental sufficiency ranges. We report pecan leaf elemental sufficiency ranges used in Oklahoma that were developed based on research in Oklahoma and elsewhere. In addition, fertilizer recommendations, based on various leaf elemental concentrations, are included.

Pecan trees subjected to different weed control and irrigation regimes from planting in 1986 through 1993 produced similar yields when irrigated (400 kg/ha, 3-yr avg) and not irrigated (320 kg/ha, 3-yr avg). Trees receiving total chemical weed control produced over five times more pecans (735 kg/ha, 3-yr avg) than weedy trees (131 kg/ha, 3-yr avg). Trees receiving disking produced more pecans when irrigated (677 kg/ha, 3-yr avg) than when not irrigated (339 kg/ha, 3-yr avg). Growth rate, expressed as increase in tree stem diameter, decreased for trees in all treatments once trees began bearing.

Yields and economic returns above treatment variable costs were determined for young `Desirable' pecan [Carya illinoinensis (Wangenh.) C. Koch] trees grown for nine seasons under ten combinations of orchard floor management practice and irrigation. Orchard floor management practices were 1) no weed control, 2) mowed, 3) total weed control with herbicides, 4) grass control only with herbicides, or 5) disking, and trees were either irrigated or nonirrigated. Total weed control with herbicides increased cumulative yield through the ninth growing season by 358% compared to no weed control. In the humid environment where this experiment was conducted, irrigation did not increase crop value obtained from the young trees, except for 1 year. At the end of the ninth season, total weed control with herbicides was the only treatment to have a positive net present value. These data indicate that establishment costs for young `Desirable' pecan trees can be recovered as early as the eighth growing season if competition from weeds is totally eliminated.

Organic mulches (leaves, pine nuggets, pine straw, grass clippings, and chipped limbs) were applied at depths of 10, 20, or 30 cm in a 3 × 3-m area around young pecan [Carya illinoinensis (Wangenh.) K. Koch] trees. These treatments were compared to an unmulched herbicide treatment and a common bermudagrass [Cynodon dactylon (L.) Pers.] sod. Trunk cross-sectional areas (TCSAs) of the mulched trees were larger than those of trees in the sod or unmulched plots and increased linearly as mulch depth increased. All mulches influenced TCSA similarly. Mean TCSA for mulched trees increased 14-fold compared to an increase of 8-fold for the unmulched trees and the sod in this 3-year study. Thus, common yard-waste mulches can be used effectively to increase growth of young pecan trees.