L. M. Carter and J. H. Chesson

OBJECTIVES: To adapt, modify or design planters and planter controls for direct seeding into cover crops.

PROCEDURE: Determine desirable and achievable planting conditions associated with direct seeding into cover crops, including type of cover crop, method of vegetation suppression and preparation prior to planting. Test operation and performance of unmodified cross slot planter designs. Design mechanisms and procedures for improving performance to acceptable levels. Investigate application of other planter designs and procedures for direct seeding into cover crops.
PROGRESS: Combining two years experience with the unmodified cross slot planter design, six conclusions can be stated: 1) the design is acceptable only within a narrow range of application which includes the original design criteria, ie dry soil planting of grains; 2) the depth of planting varies greatly with soil tilth and moisture with all seeds; 3) the design without modification is unsuited for cotton either for planting into cover crops or into prepared soil; 4) cotton planted into cover crops with this design requires rain or simulated rain for emergence; 5) cotton planted into prepared moist soil did not emerge or the emergence was well below any acceptable standard;
6) cotton planted into dry prepared soil with postplant irrigation emerged acceptably.

     The heavy footprint of the gage-wheel-furrow-closure component was determined to be the cause of poor performance as described in conclusions 2, 3, 4, and 5. A mechanical-hydraulic servo control was designed as a combination seed depth control and footprint pressure control. The design was tested and found to perform as anticipated allowing control of seed depth within .25 inch and accurate control of footprint pressure. With the control operating seed emergence in prepared moist soil was comparable to ‘normal’ planters. With cover crops, the closure pressing could be increased and controlled for improved, if not completely adequate, emergence. The mechanism for the control was described for possible patent and therefore has not been disclosed to the public. Application to other existing designs was claimed in the patent description.

FUTURE PLANS:
The operating parameters of the control will be documented and will be determined. Depending upon interest, the control may be developed for technology transfer beyond publication of any potential patent.

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L. M. Carter and J. H. Chesson

OBJECTIVES: To develop apparatus and instrumentation for field scale survey-measuring salinity based upon theories developed by the USDA Salinity Laboratory, Riverside, CA.

PROCEDURE: The probe design was based upon earlier reported research by Carter. In concept the probe compacts a ribbon of soil .75 inch wide at the depth of operation using a curved wedge. The soil strain of .5 inch has been determined in the past for maximum mechanical compaction. To remove the surface organic material from the contact area, a forward sweeping tine was attached to the front of the probe. A five probe design, rather than the classical 4-probe design, was chosen to allow symmetrical operation behind a tractor in bedded soils. This configuration allows a probe in each of 5 furrows with the inter- probe distance fixed at the row spacing. For non-bedded soils the inter-probe distance can be varied between 20 and 42 inches. A folding 3-point mounting tool bar was designed with a detachable highway compatible truck for transportation behind a pickup. The system was designed so that one or two people could attach the tool to a tractor and prepare the system for operation within 5 minutes.

RESULTS: The system was tested in dry and wet soils without instrumentation for integrity as a tillage tool. Operation was found feasible beyond 6 mph. The instrumentation package was attached including the 5 probe monitor and geographic position sensor. The instrumentation was calibrated by Dr. Rhoades in a
very saline soil.

FUTURE PLANS: The system will be field calibrated for variability with respect to speed, moisture, and soil types and field tested for suitability to task as the Shafter contribution to the cooperative program. At completion the system will be used to map salinity of several large agricultural areas. The future plans include development of a method and apparatus to utilize a electromagnetic sensor as a measure for salinity.

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L. M. Carter, W. c. Hofmann, and J. H. Chesson

OBJECTIVES: 1. To determine the efficacy of deep application of a fumigating nematocide. 2. To develop safe and environmental acceptable methods of applying nematocides.

PROCEDURE: The 1990 study consisted of 6 treatments: a control plot with normal tillage and no nematicide (treatment A); a normal 8 gallon per acre (gpa) Telone application with 2 shanks 10 inches to each side of the intended drill operated 10 inches deep (treatment B); a 22 inch deep precision tillage control plot with no nematicide (treatment C); and 22 inch deep precision tillage application at rates of 4, 6, and 8 gpa of Telone (treatments D, E, and F). The precision tillage tool consisted of two 32-inch long sub-soil shanks mounted to a tool bar with disk type bedders mounted behind the bar on pivoting arms which allowed constant depth of furrowing. The subsoil shanks had a forward angle of 15 degrees and were operated 22 inches deep from original soil level (depth from the top of the resulting bed was approximately 32 to 34 inches) . For nematocide application, a .25 inch ID tube was welded to the trailing edge of the subsoil shanks to release the nematocide at the bottom of the slot. All nematocide treatments were applied with an experimental metering device which was controlled by ground speed and depth. A peristaltic metering pump was used for each applicator. The speed of the meter was controlled by a electro/hydraulic servo commanded by a rotary pulse sensor attached to the ground metering wheel. The metering wheel was mounted such that the meter would only operate when the shanks were deeper than 50% of the intended depth. The field chosen was known to have a high and fairly uniform population of nematodes. The treatments were applied in a latin square design (6 replications) to allow greater control over nematode population variability. Two weeks after treatment application but before planting cotton, soil samples from the 1st, 2nd, and 3rd foot were obtained from each plot and placed in small pots with a seedling tomato plant. An estimate of the initial nematode population for each plot was obtained by rating the degree of nematode galling in the tomato roots on a scale of 0 to 4 with 0 indicating no galling and 4 indicating severe galling.

RESULTS: Predictably, the application of 8 gpa of Telone with a normal application reduced the galling on tomatoes to a low level. However, that same reduction was obtained with 6 gpa applied with precision tillage. Even at the 4 gpa rate applied with precision tillage the nematode galling was drastically -2- reduced suggesting that the efficiency of Telone can be substantially improved with deep application. Both applications methods were most effective in reducing the population in the second foot. We believe it is important to note that the effectiveness was greater for precision tillage application in the third foot compared to normal application. There was an improvement in cotton yield related to precision tillage and to rate of Telone. With no nematicide, precision tillage increased the yield by 10%. However at 8 gpa of Telone the increase for precision tillage (tillage effect only) was 34%. The increase in yield with 8 gpa using normal application equipment was 16%. One way of interpreting these data is that precision tillage reduced the soil compaction limitation to root extension and the Telone reduced the nematode population, each contributing the increased yields. However, when the tillage effect and the nematocide are combined, the yield increase is greater than the sum of the individual effects. Perhaps a more important interpretation is that the low rate of 4 gpa of Telone applied with precision tillage produced a 19% yield increase compared to 8 gpa applied with normal equipment. These data suggest the possibility of dramatically reducing the applied rate of Telone with equal or better yields. An application of these findings could result in a two-fold advantage for the farmer, 1) lower input cost with greater yield and 2) reduced chemical applied to the soil and therefore less release to the air. The metering system was judged to be practical for use by farmers. For farmer use, 1) higher quality (ie longer life) peristaltic meters should be purchased, 2) commercial sized, approved tanks, tubing and valves would be needed, and 3) the supply tubes to each shank should be equipped with a positive pressure-operated check valve. The experimental system prevented leakage during turns and reduced variation in application rate resulting from wheel slippage and acceleration or deceleration at ends of fields. With the deep application, there was absolutely no noticeable odor of the Telone suggesting that the method may meet the most stringent environmental rules.

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